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64db4cff PM |
1 | /* |
2 | * Read-Copy Update mechanism for mutual exclusion | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License as published by | |
6 | * the Free Software Foundation; either version 2 of the License, or | |
7 | * (at your option) any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
15 | * along with this program; if not, write to the Free Software | |
16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
17 | * | |
18 | * Copyright IBM Corporation, 2008 | |
19 | * | |
20 | * Authors: Dipankar Sarma <dipankar@in.ibm.com> | |
21 | * Manfred Spraul <manfred@colorfullife.com> | |
22 | * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version | |
23 | * | |
24 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> | |
25 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. | |
26 | * | |
27 | * For detailed explanation of Read-Copy Update mechanism see - | |
a71fca58 | 28 | * Documentation/RCU |
64db4cff PM |
29 | */ |
30 | #include <linux/types.h> | |
31 | #include <linux/kernel.h> | |
32 | #include <linux/init.h> | |
33 | #include <linux/spinlock.h> | |
34 | #include <linux/smp.h> | |
35 | #include <linux/rcupdate.h> | |
36 | #include <linux/interrupt.h> | |
37 | #include <linux/sched.h> | |
c1dc0b9c | 38 | #include <linux/nmi.h> |
8826f3b0 | 39 | #include <linux/atomic.h> |
64db4cff | 40 | #include <linux/bitops.h> |
9984de1a | 41 | #include <linux/export.h> |
64db4cff PM |
42 | #include <linux/completion.h> |
43 | #include <linux/moduleparam.h> | |
44 | #include <linux/percpu.h> | |
45 | #include <linux/notifier.h> | |
46 | #include <linux/cpu.h> | |
47 | #include <linux/mutex.h> | |
48 | #include <linux/time.h> | |
bbad9379 | 49 | #include <linux/kernel_stat.h> |
a26ac245 PM |
50 | #include <linux/wait.h> |
51 | #include <linux/kthread.h> | |
268bb0ce | 52 | #include <linux/prefetch.h> |
3d3b7db0 PM |
53 | #include <linux/delay.h> |
54 | #include <linux/stop_machine.h> | |
661a85dc | 55 | #include <linux/random.h> |
64db4cff | 56 | |
9f77da9f | 57 | #include "rcutree.h" |
29c00b4a PM |
58 | #include <trace/events/rcu.h> |
59 | ||
60 | #include "rcu.h" | |
9f77da9f | 61 | |
64db4cff PM |
62 | /* Data structures. */ |
63 | ||
f885b7f2 | 64 | static struct lock_class_key rcu_node_class[RCU_NUM_LVLS]; |
394f2769 | 65 | static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS]; |
88b91c7c | 66 | |
037b64ed | 67 | #define RCU_STATE_INITIALIZER(sname, cr) { \ |
6c90cc7b | 68 | .level = { &sname##_state.node[0] }, \ |
037b64ed | 69 | .call = cr, \ |
af446b70 | 70 | .fqs_state = RCU_GP_IDLE, \ |
64db4cff PM |
71 | .gpnum = -300, \ |
72 | .completed = -300, \ | |
6c90cc7b PM |
73 | .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.onofflock), \ |
74 | .orphan_nxttail = &sname##_state.orphan_nxtlist, \ | |
75 | .orphan_donetail = &sname##_state.orphan_donelist, \ | |
7be7f0be | 76 | .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \ |
6c90cc7b | 77 | .name = #sname, \ |
64db4cff PM |
78 | } |
79 | ||
037b64ed PM |
80 | struct rcu_state rcu_sched_state = |
81 | RCU_STATE_INITIALIZER(rcu_sched, call_rcu_sched); | |
d6714c22 | 82 | DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); |
64db4cff | 83 | |
037b64ed | 84 | struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh, call_rcu_bh); |
6258c4fb | 85 | DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); |
b1f77b05 | 86 | |
27f4d280 | 87 | static struct rcu_state *rcu_state; |
6ce75a23 | 88 | LIST_HEAD(rcu_struct_flavors); |
27f4d280 | 89 | |
f885b7f2 PM |
90 | /* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */ |
91 | static int rcu_fanout_leaf = CONFIG_RCU_FANOUT_LEAF; | |
7e5c2dfb | 92 | module_param(rcu_fanout_leaf, int, 0444); |
f885b7f2 PM |
93 | int rcu_num_lvls __read_mostly = RCU_NUM_LVLS; |
94 | static int num_rcu_lvl[] = { /* Number of rcu_nodes at specified level. */ | |
95 | NUM_RCU_LVL_0, | |
96 | NUM_RCU_LVL_1, | |
97 | NUM_RCU_LVL_2, | |
98 | NUM_RCU_LVL_3, | |
99 | NUM_RCU_LVL_4, | |
100 | }; | |
101 | int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ | |
102 | ||
b0d30417 PM |
103 | /* |
104 | * The rcu_scheduler_active variable transitions from zero to one just | |
105 | * before the first task is spawned. So when this variable is zero, RCU | |
106 | * can assume that there is but one task, allowing RCU to (for example) | |
107 | * optimized synchronize_sched() to a simple barrier(). When this variable | |
108 | * is one, RCU must actually do all the hard work required to detect real | |
109 | * grace periods. This variable is also used to suppress boot-time false | |
110 | * positives from lockdep-RCU error checking. | |
111 | */ | |
bbad9379 PM |
112 | int rcu_scheduler_active __read_mostly; |
113 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); | |
114 | ||
b0d30417 PM |
115 | /* |
116 | * The rcu_scheduler_fully_active variable transitions from zero to one | |
117 | * during the early_initcall() processing, which is after the scheduler | |
118 | * is capable of creating new tasks. So RCU processing (for example, | |
119 | * creating tasks for RCU priority boosting) must be delayed until after | |
120 | * rcu_scheduler_fully_active transitions from zero to one. We also | |
121 | * currently delay invocation of any RCU callbacks until after this point. | |
122 | * | |
123 | * It might later prove better for people registering RCU callbacks during | |
124 | * early boot to take responsibility for these callbacks, but one step at | |
125 | * a time. | |
126 | */ | |
127 | static int rcu_scheduler_fully_active __read_mostly; | |
128 | ||
a46e0899 PM |
129 | #ifdef CONFIG_RCU_BOOST |
130 | ||
a26ac245 PM |
131 | /* |
132 | * Control variables for per-CPU and per-rcu_node kthreads. These | |
133 | * handle all flavors of RCU. | |
134 | */ | |
135 | static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); | |
d71df90e | 136 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); |
5ece5bab | 137 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); |
d71df90e | 138 | DEFINE_PER_CPU(char, rcu_cpu_has_work); |
a26ac245 | 139 | |
a46e0899 PM |
140 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
141 | ||
5d01bbd1 | 142 | static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); |
a46e0899 PM |
143 | static void invoke_rcu_core(void); |
144 | static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp); | |
a26ac245 | 145 | |
4a298656 PM |
146 | /* |
147 | * Track the rcutorture test sequence number and the update version | |
148 | * number within a given test. The rcutorture_testseq is incremented | |
149 | * on every rcutorture module load and unload, so has an odd value | |
150 | * when a test is running. The rcutorture_vernum is set to zero | |
151 | * when rcutorture starts and is incremented on each rcutorture update. | |
152 | * These variables enable correlating rcutorture output with the | |
153 | * RCU tracing information. | |
154 | */ | |
155 | unsigned long rcutorture_testseq; | |
156 | unsigned long rcutorture_vernum; | |
157 | ||
fc2219d4 PM |
158 | /* |
159 | * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s | |
160 | * permit this function to be invoked without holding the root rcu_node | |
161 | * structure's ->lock, but of course results can be subject to change. | |
162 | */ | |
163 | static int rcu_gp_in_progress(struct rcu_state *rsp) | |
164 | { | |
165 | return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); | |
166 | } | |
167 | ||
b1f77b05 | 168 | /* |
d6714c22 | 169 | * Note a quiescent state. Because we do not need to know |
b1f77b05 | 170 | * how many quiescent states passed, just if there was at least |
d6714c22 | 171 | * one since the start of the grace period, this just sets a flag. |
e4cc1f22 | 172 | * The caller must have disabled preemption. |
b1f77b05 | 173 | */ |
d6714c22 | 174 | void rcu_sched_qs(int cpu) |
b1f77b05 | 175 | { |
25502a6c | 176 | struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); |
f41d911f | 177 | |
e4cc1f22 | 178 | if (rdp->passed_quiesce == 0) |
d4c08f2a | 179 | trace_rcu_grace_period("rcu_sched", rdp->gpnum, "cpuqs"); |
e4cc1f22 | 180 | rdp->passed_quiesce = 1; |
b1f77b05 IM |
181 | } |
182 | ||
d6714c22 | 183 | void rcu_bh_qs(int cpu) |
b1f77b05 | 184 | { |
25502a6c | 185 | struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); |
f41d911f | 186 | |
e4cc1f22 | 187 | if (rdp->passed_quiesce == 0) |
d4c08f2a | 188 | trace_rcu_grace_period("rcu_bh", rdp->gpnum, "cpuqs"); |
e4cc1f22 | 189 | rdp->passed_quiesce = 1; |
b1f77b05 | 190 | } |
64db4cff | 191 | |
25502a6c PM |
192 | /* |
193 | * Note a context switch. This is a quiescent state for RCU-sched, | |
194 | * and requires special handling for preemptible RCU. | |
e4cc1f22 | 195 | * The caller must have disabled preemption. |
25502a6c PM |
196 | */ |
197 | void rcu_note_context_switch(int cpu) | |
198 | { | |
300df91c | 199 | trace_rcu_utilization("Start context switch"); |
25502a6c | 200 | rcu_sched_qs(cpu); |
cba6d0d6 | 201 | rcu_preempt_note_context_switch(cpu); |
300df91c | 202 | trace_rcu_utilization("End context switch"); |
25502a6c | 203 | } |
29ce8310 | 204 | EXPORT_SYMBOL_GPL(rcu_note_context_switch); |
25502a6c | 205 | |
90a4d2c0 | 206 | DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
29e37d81 | 207 | .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE, |
23b5c8fa | 208 | .dynticks = ATOMIC_INIT(1), |
1fd2b442 | 209 | #if defined(CONFIG_RCU_USER_QS) && !defined(CONFIG_RCU_USER_QS_FORCE) |
1e1a689f FW |
210 | .ignore_user_qs = true, |
211 | #endif | |
90a4d2c0 | 212 | }; |
64db4cff | 213 | |
e0f23060 | 214 | static int blimit = 10; /* Maximum callbacks per rcu_do_batch. */ |
64db4cff PM |
215 | static int qhimark = 10000; /* If this many pending, ignore blimit. */ |
216 | static int qlowmark = 100; /* Once only this many pending, use blimit. */ | |
217 | ||
7e5c2dfb PM |
218 | module_param(blimit, int, 0444); |
219 | module_param(qhimark, int, 0444); | |
220 | module_param(qlowmark, int, 0444); | |
3d76c082 | 221 | |
13cfcca0 PM |
222 | int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */ |
223 | int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT; | |
224 | ||
f2e0dd70 | 225 | module_param(rcu_cpu_stall_suppress, int, 0644); |
13cfcca0 | 226 | module_param(rcu_cpu_stall_timeout, int, 0644); |
742734ee | 227 | |
d40011f6 PM |
228 | static ulong jiffies_till_first_fqs = RCU_JIFFIES_TILL_FORCE_QS; |
229 | static ulong jiffies_till_next_fqs = RCU_JIFFIES_TILL_FORCE_QS; | |
230 | ||
231 | module_param(jiffies_till_first_fqs, ulong, 0644); | |
232 | module_param(jiffies_till_next_fqs, ulong, 0644); | |
233 | ||
4cdfc175 PM |
234 | static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)); |
235 | static void force_quiescent_state(struct rcu_state *rsp); | |
a157229c | 236 | static int rcu_pending(int cpu); |
64db4cff PM |
237 | |
238 | /* | |
d6714c22 | 239 | * Return the number of RCU-sched batches processed thus far for debug & stats. |
64db4cff | 240 | */ |
d6714c22 | 241 | long rcu_batches_completed_sched(void) |
64db4cff | 242 | { |
d6714c22 | 243 | return rcu_sched_state.completed; |
64db4cff | 244 | } |
d6714c22 | 245 | EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
64db4cff PM |
246 | |
247 | /* | |
248 | * Return the number of RCU BH batches processed thus far for debug & stats. | |
249 | */ | |
250 | long rcu_batches_completed_bh(void) | |
251 | { | |
252 | return rcu_bh_state.completed; | |
253 | } | |
254 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); | |
255 | ||
bf66f18e PM |
256 | /* |
257 | * Force a quiescent state for RCU BH. | |
258 | */ | |
259 | void rcu_bh_force_quiescent_state(void) | |
260 | { | |
4cdfc175 | 261 | force_quiescent_state(&rcu_bh_state); |
bf66f18e PM |
262 | } |
263 | EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); | |
264 | ||
4a298656 PM |
265 | /* |
266 | * Record the number of times rcutorture tests have been initiated and | |
267 | * terminated. This information allows the debugfs tracing stats to be | |
268 | * correlated to the rcutorture messages, even when the rcutorture module | |
269 | * is being repeatedly loaded and unloaded. In other words, we cannot | |
270 | * store this state in rcutorture itself. | |
271 | */ | |
272 | void rcutorture_record_test_transition(void) | |
273 | { | |
274 | rcutorture_testseq++; | |
275 | rcutorture_vernum = 0; | |
276 | } | |
277 | EXPORT_SYMBOL_GPL(rcutorture_record_test_transition); | |
278 | ||
279 | /* | |
280 | * Record the number of writer passes through the current rcutorture test. | |
281 | * This is also used to correlate debugfs tracing stats with the rcutorture | |
282 | * messages. | |
283 | */ | |
284 | void rcutorture_record_progress(unsigned long vernum) | |
285 | { | |
286 | rcutorture_vernum++; | |
287 | } | |
288 | EXPORT_SYMBOL_GPL(rcutorture_record_progress); | |
289 | ||
bf66f18e PM |
290 | /* |
291 | * Force a quiescent state for RCU-sched. | |
292 | */ | |
293 | void rcu_sched_force_quiescent_state(void) | |
294 | { | |
4cdfc175 | 295 | force_quiescent_state(&rcu_sched_state); |
bf66f18e PM |
296 | } |
297 | EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); | |
298 | ||
64db4cff PM |
299 | /* |
300 | * Does the CPU have callbacks ready to be invoked? | |
301 | */ | |
302 | static int | |
303 | cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) | |
304 | { | |
305 | return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]; | |
306 | } | |
307 | ||
308 | /* | |
309 | * Does the current CPU require a yet-as-unscheduled grace period? | |
310 | */ | |
311 | static int | |
312 | cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) | |
313 | { | |
a10d206e PM |
314 | return *rdp->nxttail[RCU_DONE_TAIL + |
315 | ACCESS_ONCE(rsp->completed) != rdp->completed] && | |
316 | !rcu_gp_in_progress(rsp); | |
64db4cff PM |
317 | } |
318 | ||
319 | /* | |
320 | * Return the root node of the specified rcu_state structure. | |
321 | */ | |
322 | static struct rcu_node *rcu_get_root(struct rcu_state *rsp) | |
323 | { | |
324 | return &rsp->node[0]; | |
325 | } | |
326 | ||
9b2e4f18 | 327 | /* |
adf5091e | 328 | * rcu_eqs_enter_common - current CPU is moving towards extended quiescent state |
9b2e4f18 PM |
329 | * |
330 | * If the new value of the ->dynticks_nesting counter now is zero, | |
331 | * we really have entered idle, and must do the appropriate accounting. | |
332 | * The caller must have disabled interrupts. | |
333 | */ | |
adf5091e FW |
334 | static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval, |
335 | bool user) | |
9b2e4f18 | 336 | { |
facc4e15 | 337 | trace_rcu_dyntick("Start", oldval, 0); |
cb349ca9 | 338 | if (!user && !is_idle_task(current)) { |
0989cb46 PM |
339 | struct task_struct *idle = idle_task(smp_processor_id()); |
340 | ||
facc4e15 | 341 | trace_rcu_dyntick("Error on entry: not idle task", oldval, 0); |
bf1304e9 | 342 | ftrace_dump(DUMP_ORIG); |
0989cb46 PM |
343 | WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
344 | current->pid, current->comm, | |
345 | idle->pid, idle->comm); /* must be idle task! */ | |
9b2e4f18 | 346 | } |
aea1b35e | 347 | rcu_prepare_for_idle(smp_processor_id()); |
9b2e4f18 PM |
348 | /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
349 | smp_mb__before_atomic_inc(); /* See above. */ | |
350 | atomic_inc(&rdtp->dynticks); | |
351 | smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */ | |
352 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); | |
c44e2cdd PM |
353 | |
354 | /* | |
adf5091e | 355 | * It is illegal to enter an extended quiescent state while |
c44e2cdd PM |
356 | * in an RCU read-side critical section. |
357 | */ | |
358 | rcu_lockdep_assert(!lock_is_held(&rcu_lock_map), | |
359 | "Illegal idle entry in RCU read-side critical section."); | |
360 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), | |
361 | "Illegal idle entry in RCU-bh read-side critical section."); | |
362 | rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), | |
363 | "Illegal idle entry in RCU-sched read-side critical section."); | |
9b2e4f18 | 364 | } |
64db4cff | 365 | |
adf5091e FW |
366 | /* |
367 | * Enter an RCU extended quiescent state, which can be either the | |
368 | * idle loop or adaptive-tickless usermode execution. | |
64db4cff | 369 | */ |
adf5091e | 370 | static void rcu_eqs_enter(bool user) |
64db4cff | 371 | { |
4145fa7f | 372 | long long oldval; |
64db4cff PM |
373 | struct rcu_dynticks *rdtp; |
374 | ||
64db4cff | 375 | rdtp = &__get_cpu_var(rcu_dynticks); |
4145fa7f | 376 | oldval = rdtp->dynticks_nesting; |
29e37d81 PM |
377 | WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0); |
378 | if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) | |
379 | rdtp->dynticks_nesting = 0; | |
380 | else | |
381 | rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE; | |
adf5091e | 382 | rcu_eqs_enter_common(rdtp, oldval, user); |
64db4cff | 383 | } |
adf5091e FW |
384 | |
385 | /** | |
386 | * rcu_idle_enter - inform RCU that current CPU is entering idle | |
387 | * | |
388 | * Enter idle mode, in other words, -leave- the mode in which RCU | |
389 | * read-side critical sections can occur. (Though RCU read-side | |
390 | * critical sections can occur in irq handlers in idle, a possibility | |
391 | * handled by irq_enter() and irq_exit().) | |
392 | * | |
393 | * We crowbar the ->dynticks_nesting field to zero to allow for | |
394 | * the possibility of usermode upcalls having messed up our count | |
395 | * of interrupt nesting level during the prior busy period. | |
396 | */ | |
397 | void rcu_idle_enter(void) | |
398 | { | |
c5d900bf FW |
399 | unsigned long flags; |
400 | ||
401 | local_irq_save(flags); | |
cb349ca9 | 402 | rcu_eqs_enter(false); |
c5d900bf | 403 | local_irq_restore(flags); |
adf5091e | 404 | } |
8a2ecf47 | 405 | EXPORT_SYMBOL_GPL(rcu_idle_enter); |
64db4cff | 406 | |
2b1d5024 | 407 | #ifdef CONFIG_RCU_USER_QS |
adf5091e FW |
408 | /** |
409 | * rcu_user_enter - inform RCU that we are resuming userspace. | |
410 | * | |
411 | * Enter RCU idle mode right before resuming userspace. No use of RCU | |
412 | * is permitted between this call and rcu_user_exit(). This way the | |
413 | * CPU doesn't need to maintain the tick for RCU maintenance purposes | |
414 | * when the CPU runs in userspace. | |
415 | */ | |
416 | void rcu_user_enter(void) | |
417 | { | |
c5d900bf FW |
418 | unsigned long flags; |
419 | struct rcu_dynticks *rdtp; | |
420 | ||
adf5091e FW |
421 | /* |
422 | * Some contexts may involve an exception occuring in an irq, | |
423 | * leading to that nesting: | |
424 | * rcu_irq_enter() rcu_user_exit() rcu_user_exit() rcu_irq_exit() | |
425 | * This would mess up the dyntick_nesting count though. And rcu_irq_*() | |
426 | * helpers are enough to protect RCU uses inside the exception. So | |
427 | * just return immediately if we detect we are in an IRQ. | |
428 | */ | |
429 | if (in_interrupt()) | |
430 | return; | |
431 | ||
c5d900bf FW |
432 | WARN_ON_ONCE(!current->mm); |
433 | ||
434 | local_irq_save(flags); | |
435 | rdtp = &__get_cpu_var(rcu_dynticks); | |
1e1a689f | 436 | if (!rdtp->ignore_user_qs && !rdtp->in_user) { |
c5d900bf | 437 | rdtp->in_user = true; |
cb349ca9 | 438 | rcu_eqs_enter(true); |
c5d900bf FW |
439 | } |
440 | local_irq_restore(flags); | |
adf5091e FW |
441 | } |
442 | ||
19dd1591 FW |
443 | /** |
444 | * rcu_user_enter_after_irq - inform RCU that we are going to resume userspace | |
445 | * after the current irq returns. | |
446 | * | |
447 | * This is similar to rcu_user_enter() but in the context of a non-nesting | |
448 | * irq. After this call, RCU enters into idle mode when the interrupt | |
449 | * returns. | |
450 | */ | |
451 | void rcu_user_enter_after_irq(void) | |
452 | { | |
453 | unsigned long flags; | |
454 | struct rcu_dynticks *rdtp; | |
455 | ||
456 | local_irq_save(flags); | |
457 | rdtp = &__get_cpu_var(rcu_dynticks); | |
458 | /* Ensure this irq is interrupting a non-idle RCU state. */ | |
459 | WARN_ON_ONCE(!(rdtp->dynticks_nesting & DYNTICK_TASK_MASK)); | |
460 | rdtp->dynticks_nesting = 1; | |
461 | local_irq_restore(flags); | |
462 | } | |
2b1d5024 | 463 | #endif /* CONFIG_RCU_USER_QS */ |
19dd1591 | 464 | |
9b2e4f18 PM |
465 | /** |
466 | * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle | |
467 | * | |
468 | * Exit from an interrupt handler, which might possibly result in entering | |
469 | * idle mode, in other words, leaving the mode in which read-side critical | |
470 | * sections can occur. | |
64db4cff | 471 | * |
9b2e4f18 PM |
472 | * This code assumes that the idle loop never does anything that might |
473 | * result in unbalanced calls to irq_enter() and irq_exit(). If your | |
474 | * architecture violates this assumption, RCU will give you what you | |
475 | * deserve, good and hard. But very infrequently and irreproducibly. | |
476 | * | |
477 | * Use things like work queues to work around this limitation. | |
478 | * | |
479 | * You have been warned. | |
64db4cff | 480 | */ |
9b2e4f18 | 481 | void rcu_irq_exit(void) |
64db4cff PM |
482 | { |
483 | unsigned long flags; | |
4145fa7f | 484 | long long oldval; |
64db4cff PM |
485 | struct rcu_dynticks *rdtp; |
486 | ||
487 | local_irq_save(flags); | |
488 | rdtp = &__get_cpu_var(rcu_dynticks); | |
4145fa7f | 489 | oldval = rdtp->dynticks_nesting; |
9b2e4f18 PM |
490 | rdtp->dynticks_nesting--; |
491 | WARN_ON_ONCE(rdtp->dynticks_nesting < 0); | |
b6fc6020 FW |
492 | if (rdtp->dynticks_nesting) |
493 | trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting); | |
494 | else | |
cb349ca9 | 495 | rcu_eqs_enter_common(rdtp, oldval, true); |
9b2e4f18 PM |
496 | local_irq_restore(flags); |
497 | } | |
498 | ||
499 | /* | |
adf5091e | 500 | * rcu_eqs_exit_common - current CPU moving away from extended quiescent state |
9b2e4f18 PM |
501 | * |
502 | * If the new value of the ->dynticks_nesting counter was previously zero, | |
503 | * we really have exited idle, and must do the appropriate accounting. | |
504 | * The caller must have disabled interrupts. | |
505 | */ | |
adf5091e FW |
506 | static void rcu_eqs_exit_common(struct rcu_dynticks *rdtp, long long oldval, |
507 | int user) | |
9b2e4f18 | 508 | { |
23b5c8fa PM |
509 | smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */ |
510 | atomic_inc(&rdtp->dynticks); | |
511 | /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ | |
512 | smp_mb__after_atomic_inc(); /* See above. */ | |
513 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); | |
7cb92499 | 514 | rcu_cleanup_after_idle(smp_processor_id()); |
4145fa7f | 515 | trace_rcu_dyntick("End", oldval, rdtp->dynticks_nesting); |
cb349ca9 | 516 | if (!user && !is_idle_task(current)) { |
0989cb46 PM |
517 | struct task_struct *idle = idle_task(smp_processor_id()); |
518 | ||
4145fa7f PM |
519 | trace_rcu_dyntick("Error on exit: not idle task", |
520 | oldval, rdtp->dynticks_nesting); | |
bf1304e9 | 521 | ftrace_dump(DUMP_ORIG); |
0989cb46 PM |
522 | WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
523 | current->pid, current->comm, | |
524 | idle->pid, idle->comm); /* must be idle task! */ | |
9b2e4f18 PM |
525 | } |
526 | } | |
527 | ||
adf5091e FW |
528 | /* |
529 | * Exit an RCU extended quiescent state, which can be either the | |
530 | * idle loop or adaptive-tickless usermode execution. | |
9b2e4f18 | 531 | */ |
adf5091e | 532 | static void rcu_eqs_exit(bool user) |
9b2e4f18 | 533 | { |
9b2e4f18 PM |
534 | struct rcu_dynticks *rdtp; |
535 | long long oldval; | |
536 | ||
9b2e4f18 PM |
537 | rdtp = &__get_cpu_var(rcu_dynticks); |
538 | oldval = rdtp->dynticks_nesting; | |
29e37d81 PM |
539 | WARN_ON_ONCE(oldval < 0); |
540 | if (oldval & DYNTICK_TASK_NEST_MASK) | |
541 | rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE; | |
542 | else | |
543 | rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; | |
adf5091e | 544 | rcu_eqs_exit_common(rdtp, oldval, user); |
9b2e4f18 | 545 | } |
adf5091e FW |
546 | |
547 | /** | |
548 | * rcu_idle_exit - inform RCU that current CPU is leaving idle | |
549 | * | |
550 | * Exit idle mode, in other words, -enter- the mode in which RCU | |
551 | * read-side critical sections can occur. | |
552 | * | |
553 | * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to | |
554 | * allow for the possibility of usermode upcalls messing up our count | |
555 | * of interrupt nesting level during the busy period that is just | |
556 | * now starting. | |
557 | */ | |
558 | void rcu_idle_exit(void) | |
559 | { | |
c5d900bf FW |
560 | unsigned long flags; |
561 | ||
562 | local_irq_save(flags); | |
cb349ca9 | 563 | rcu_eqs_exit(false); |
c5d900bf | 564 | local_irq_restore(flags); |
adf5091e | 565 | } |
8a2ecf47 | 566 | EXPORT_SYMBOL_GPL(rcu_idle_exit); |
9b2e4f18 | 567 | |
2b1d5024 | 568 | #ifdef CONFIG_RCU_USER_QS |
adf5091e FW |
569 | /** |
570 | * rcu_user_exit - inform RCU that we are exiting userspace. | |
571 | * | |
572 | * Exit RCU idle mode while entering the kernel because it can | |
573 | * run a RCU read side critical section anytime. | |
574 | */ | |
575 | void rcu_user_exit(void) | |
576 | { | |
c5d900bf FW |
577 | unsigned long flags; |
578 | struct rcu_dynticks *rdtp; | |
579 | ||
adf5091e FW |
580 | /* |
581 | * Some contexts may involve an exception occuring in an irq, | |
582 | * leading to that nesting: | |
583 | * rcu_irq_enter() rcu_user_exit() rcu_user_exit() rcu_irq_exit() | |
584 | * This would mess up the dyntick_nesting count though. And rcu_irq_*() | |
585 | * helpers are enough to protect RCU uses inside the exception. So | |
586 | * just return immediately if we detect we are in an IRQ. | |
587 | */ | |
588 | if (in_interrupt()) | |
589 | return; | |
590 | ||
c5d900bf FW |
591 | local_irq_save(flags); |
592 | rdtp = &__get_cpu_var(rcu_dynticks); | |
593 | if (rdtp->in_user) { | |
594 | rdtp->in_user = false; | |
cb349ca9 | 595 | rcu_eqs_exit(true); |
c5d900bf FW |
596 | } |
597 | local_irq_restore(flags); | |
adf5091e FW |
598 | } |
599 | ||
19dd1591 FW |
600 | /** |
601 | * rcu_user_exit_after_irq - inform RCU that we won't resume to userspace | |
602 | * idle mode after the current non-nesting irq returns. | |
603 | * | |
604 | * This is similar to rcu_user_exit() but in the context of an irq. | |
605 | * This is called when the irq has interrupted a userspace RCU idle mode | |
606 | * context. When the current non-nesting interrupt returns after this call, | |
607 | * the CPU won't restore the RCU idle mode. | |
608 | */ | |
609 | void rcu_user_exit_after_irq(void) | |
610 | { | |
611 | unsigned long flags; | |
612 | struct rcu_dynticks *rdtp; | |
613 | ||
614 | local_irq_save(flags); | |
615 | rdtp = &__get_cpu_var(rcu_dynticks); | |
616 | /* Ensure we are interrupting an RCU idle mode. */ | |
617 | WARN_ON_ONCE(rdtp->dynticks_nesting & DYNTICK_TASK_NEST_MASK); | |
618 | rdtp->dynticks_nesting += DYNTICK_TASK_EXIT_IDLE; | |
619 | local_irq_restore(flags); | |
620 | } | |
2b1d5024 | 621 | #endif /* CONFIG_RCU_USER_QS */ |
19dd1591 | 622 | |
9b2e4f18 PM |
623 | /** |
624 | * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle | |
625 | * | |
626 | * Enter an interrupt handler, which might possibly result in exiting | |
627 | * idle mode, in other words, entering the mode in which read-side critical | |
628 | * sections can occur. | |
629 | * | |
630 | * Note that the Linux kernel is fully capable of entering an interrupt | |
631 | * handler that it never exits, for example when doing upcalls to | |
632 | * user mode! This code assumes that the idle loop never does upcalls to | |
633 | * user mode. If your architecture does do upcalls from the idle loop (or | |
634 | * does anything else that results in unbalanced calls to the irq_enter() | |
635 | * and irq_exit() functions), RCU will give you what you deserve, good | |
636 | * and hard. But very infrequently and irreproducibly. | |
637 | * | |
638 | * Use things like work queues to work around this limitation. | |
639 | * | |
640 | * You have been warned. | |
641 | */ | |
642 | void rcu_irq_enter(void) | |
643 | { | |
644 | unsigned long flags; | |
645 | struct rcu_dynticks *rdtp; | |
646 | long long oldval; | |
647 | ||
648 | local_irq_save(flags); | |
649 | rdtp = &__get_cpu_var(rcu_dynticks); | |
650 | oldval = rdtp->dynticks_nesting; | |
651 | rdtp->dynticks_nesting++; | |
652 | WARN_ON_ONCE(rdtp->dynticks_nesting == 0); | |
b6fc6020 FW |
653 | if (oldval) |
654 | trace_rcu_dyntick("++=", oldval, rdtp->dynticks_nesting); | |
655 | else | |
cb349ca9 | 656 | rcu_eqs_exit_common(rdtp, oldval, true); |
64db4cff | 657 | local_irq_restore(flags); |
64db4cff PM |
658 | } |
659 | ||
660 | /** | |
661 | * rcu_nmi_enter - inform RCU of entry to NMI context | |
662 | * | |
663 | * If the CPU was idle with dynamic ticks active, and there is no | |
664 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
665 | * RCU grace-period handling know that the CPU is active. | |
666 | */ | |
667 | void rcu_nmi_enter(void) | |
668 | { | |
669 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
670 | ||
23b5c8fa PM |
671 | if (rdtp->dynticks_nmi_nesting == 0 && |
672 | (atomic_read(&rdtp->dynticks) & 0x1)) | |
64db4cff | 673 | return; |
23b5c8fa PM |
674 | rdtp->dynticks_nmi_nesting++; |
675 | smp_mb__before_atomic_inc(); /* Force delay from prior write. */ | |
676 | atomic_inc(&rdtp->dynticks); | |
677 | /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ | |
678 | smp_mb__after_atomic_inc(); /* See above. */ | |
679 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); | |
64db4cff PM |
680 | } |
681 | ||
682 | /** | |
683 | * rcu_nmi_exit - inform RCU of exit from NMI context | |
684 | * | |
685 | * If the CPU was idle with dynamic ticks active, and there is no | |
686 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
687 | * RCU grace-period handling know that the CPU is no longer active. | |
688 | */ | |
689 | void rcu_nmi_exit(void) | |
690 | { | |
691 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
692 | ||
23b5c8fa PM |
693 | if (rdtp->dynticks_nmi_nesting == 0 || |
694 | --rdtp->dynticks_nmi_nesting != 0) | |
64db4cff | 695 | return; |
23b5c8fa PM |
696 | /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
697 | smp_mb__before_atomic_inc(); /* See above. */ | |
698 | atomic_inc(&rdtp->dynticks); | |
699 | smp_mb__after_atomic_inc(); /* Force delay to next write. */ | |
700 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); | |
64db4cff PM |
701 | } |
702 | ||
703 | /** | |
9b2e4f18 | 704 | * rcu_is_cpu_idle - see if RCU thinks that the current CPU is idle |
64db4cff | 705 | * |
9b2e4f18 | 706 | * If the current CPU is in its idle loop and is neither in an interrupt |
34240697 | 707 | * or NMI handler, return true. |
64db4cff | 708 | */ |
9b2e4f18 | 709 | int rcu_is_cpu_idle(void) |
64db4cff | 710 | { |
34240697 PM |
711 | int ret; |
712 | ||
713 | preempt_disable(); | |
714 | ret = (atomic_read(&__get_cpu_var(rcu_dynticks).dynticks) & 0x1) == 0; | |
715 | preempt_enable(); | |
716 | return ret; | |
64db4cff | 717 | } |
e6b80a3b | 718 | EXPORT_SYMBOL(rcu_is_cpu_idle); |
64db4cff | 719 | |
04e7e951 FW |
720 | #ifdef CONFIG_RCU_USER_QS |
721 | void rcu_user_hooks_switch(struct task_struct *prev, | |
722 | struct task_struct *next) | |
723 | { | |
724 | struct rcu_dynticks *rdtp; | |
725 | ||
726 | /* Interrupts are disabled in context switch */ | |
727 | rdtp = &__get_cpu_var(rcu_dynticks); | |
728 | if (!rdtp->ignore_user_qs) { | |
729 | clear_tsk_thread_flag(prev, TIF_NOHZ); | |
730 | set_tsk_thread_flag(next, TIF_NOHZ); | |
731 | } | |
732 | } | |
733 | #endif /* #ifdef CONFIG_RCU_USER_QS */ | |
734 | ||
62fde6ed | 735 | #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) |
c0d6d01b PM |
736 | |
737 | /* | |
738 | * Is the current CPU online? Disable preemption to avoid false positives | |
739 | * that could otherwise happen due to the current CPU number being sampled, | |
740 | * this task being preempted, its old CPU being taken offline, resuming | |
741 | * on some other CPU, then determining that its old CPU is now offline. | |
742 | * It is OK to use RCU on an offline processor during initial boot, hence | |
2036d94a PM |
743 | * the check for rcu_scheduler_fully_active. Note also that it is OK |
744 | * for a CPU coming online to use RCU for one jiffy prior to marking itself | |
745 | * online in the cpu_online_mask. Similarly, it is OK for a CPU going | |
746 | * offline to continue to use RCU for one jiffy after marking itself | |
747 | * offline in the cpu_online_mask. This leniency is necessary given the | |
748 | * non-atomic nature of the online and offline processing, for example, | |
749 | * the fact that a CPU enters the scheduler after completing the CPU_DYING | |
750 | * notifiers. | |
751 | * | |
752 | * This is also why RCU internally marks CPUs online during the | |
753 | * CPU_UP_PREPARE phase and offline during the CPU_DEAD phase. | |
c0d6d01b PM |
754 | * |
755 | * Disable checking if in an NMI handler because we cannot safely report | |
756 | * errors from NMI handlers anyway. | |
757 | */ | |
758 | bool rcu_lockdep_current_cpu_online(void) | |
759 | { | |
2036d94a PM |
760 | struct rcu_data *rdp; |
761 | struct rcu_node *rnp; | |
c0d6d01b PM |
762 | bool ret; |
763 | ||
764 | if (in_nmi()) | |
765 | return 1; | |
766 | preempt_disable(); | |
2036d94a PM |
767 | rdp = &__get_cpu_var(rcu_sched_data); |
768 | rnp = rdp->mynode; | |
769 | ret = (rdp->grpmask & rnp->qsmaskinit) || | |
c0d6d01b PM |
770 | !rcu_scheduler_fully_active; |
771 | preempt_enable(); | |
772 | return ret; | |
773 | } | |
774 | EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); | |
775 | ||
62fde6ed | 776 | #endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */ |
9b2e4f18 | 777 | |
64db4cff | 778 | /** |
9b2e4f18 | 779 | * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle |
64db4cff | 780 | * |
9b2e4f18 PM |
781 | * If the current CPU is idle or running at a first-level (not nested) |
782 | * interrupt from idle, return true. The caller must have at least | |
783 | * disabled preemption. | |
64db4cff | 784 | */ |
9b2e4f18 | 785 | int rcu_is_cpu_rrupt_from_idle(void) |
64db4cff | 786 | { |
9b2e4f18 | 787 | return __get_cpu_var(rcu_dynticks).dynticks_nesting <= 1; |
64db4cff PM |
788 | } |
789 | ||
64db4cff PM |
790 | /* |
791 | * Snapshot the specified CPU's dynticks counter so that we can later | |
792 | * credit them with an implicit quiescent state. Return 1 if this CPU | |
1eba8f84 | 793 | * is in dynticks idle mode, which is an extended quiescent state. |
64db4cff PM |
794 | */ |
795 | static int dyntick_save_progress_counter(struct rcu_data *rdp) | |
796 | { | |
23b5c8fa | 797 | rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks); |
f0e7c19d | 798 | return (rdp->dynticks_snap & 0x1) == 0; |
64db4cff PM |
799 | } |
800 | ||
801 | /* | |
802 | * Return true if the specified CPU has passed through a quiescent | |
803 | * state by virtue of being in or having passed through an dynticks | |
804 | * idle state since the last call to dyntick_save_progress_counter() | |
a82dcc76 | 805 | * for this same CPU, or by virtue of having been offline. |
64db4cff PM |
806 | */ |
807 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) | |
808 | { | |
7eb4f455 PM |
809 | unsigned int curr; |
810 | unsigned int snap; | |
64db4cff | 811 | |
7eb4f455 PM |
812 | curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks); |
813 | snap = (unsigned int)rdp->dynticks_snap; | |
64db4cff PM |
814 | |
815 | /* | |
816 | * If the CPU passed through or entered a dynticks idle phase with | |
817 | * no active irq/NMI handlers, then we can safely pretend that the CPU | |
818 | * already acknowledged the request to pass through a quiescent | |
819 | * state. Either way, that CPU cannot possibly be in an RCU | |
820 | * read-side critical section that started before the beginning | |
821 | * of the current RCU grace period. | |
822 | */ | |
7eb4f455 | 823 | if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) { |
d4c08f2a | 824 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "dti"); |
64db4cff PM |
825 | rdp->dynticks_fqs++; |
826 | return 1; | |
827 | } | |
828 | ||
a82dcc76 PM |
829 | /* |
830 | * Check for the CPU being offline, but only if the grace period | |
831 | * is old enough. We don't need to worry about the CPU changing | |
832 | * state: If we see it offline even once, it has been through a | |
833 | * quiescent state. | |
834 | * | |
835 | * The reason for insisting that the grace period be at least | |
836 | * one jiffy old is that CPUs that are not quite online and that | |
837 | * have just gone offline can still execute RCU read-side critical | |
838 | * sections. | |
839 | */ | |
840 | if (ULONG_CMP_GE(rdp->rsp->gp_start + 2, jiffies)) | |
841 | return 0; /* Grace period is not old enough. */ | |
842 | barrier(); | |
843 | if (cpu_is_offline(rdp->cpu)) { | |
844 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "ofl"); | |
845 | rdp->offline_fqs++; | |
846 | return 1; | |
847 | } | |
848 | return 0; | |
64db4cff PM |
849 | } |
850 | ||
13cfcca0 PM |
851 | static int jiffies_till_stall_check(void) |
852 | { | |
853 | int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout); | |
854 | ||
855 | /* | |
856 | * Limit check must be consistent with the Kconfig limits | |
857 | * for CONFIG_RCU_CPU_STALL_TIMEOUT. | |
858 | */ | |
859 | if (till_stall_check < 3) { | |
860 | ACCESS_ONCE(rcu_cpu_stall_timeout) = 3; | |
861 | till_stall_check = 3; | |
862 | } else if (till_stall_check > 300) { | |
863 | ACCESS_ONCE(rcu_cpu_stall_timeout) = 300; | |
864 | till_stall_check = 300; | |
865 | } | |
866 | return till_stall_check * HZ + RCU_STALL_DELAY_DELTA; | |
867 | } | |
868 | ||
64db4cff PM |
869 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
870 | { | |
871 | rsp->gp_start = jiffies; | |
13cfcca0 | 872 | rsp->jiffies_stall = jiffies + jiffies_till_stall_check(); |
64db4cff PM |
873 | } |
874 | ||
875 | static void print_other_cpu_stall(struct rcu_state *rsp) | |
876 | { | |
877 | int cpu; | |
878 | long delta; | |
879 | unsigned long flags; | |
285fe294 | 880 | int ndetected = 0; |
64db4cff | 881 | struct rcu_node *rnp = rcu_get_root(rsp); |
64db4cff PM |
882 | |
883 | /* Only let one CPU complain about others per time interval. */ | |
884 | ||
1304afb2 | 885 | raw_spin_lock_irqsave(&rnp->lock, flags); |
64db4cff | 886 | delta = jiffies - rsp->jiffies_stall; |
fc2219d4 | 887 | if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
1304afb2 | 888 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
889 | return; |
890 | } | |
13cfcca0 | 891 | rsp->jiffies_stall = jiffies + 3 * jiffies_till_stall_check() + 3; |
1304afb2 | 892 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 893 | |
8cdd32a9 PM |
894 | /* |
895 | * OK, time to rat on our buddy... | |
896 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
897 | * RCU CPU stall warnings. | |
898 | */ | |
a858af28 | 899 | printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks:", |
4300aa64 | 900 | rsp->name); |
a858af28 | 901 | print_cpu_stall_info_begin(); |
a0b6c9a7 | 902 | rcu_for_each_leaf_node(rsp, rnp) { |
3acd9eb3 | 903 | raw_spin_lock_irqsave(&rnp->lock, flags); |
9bc8b558 | 904 | ndetected += rcu_print_task_stall(rnp); |
c8020a67 PM |
905 | if (rnp->qsmask != 0) { |
906 | for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) | |
907 | if (rnp->qsmask & (1UL << cpu)) { | |
908 | print_cpu_stall_info(rsp, | |
909 | rnp->grplo + cpu); | |
910 | ndetected++; | |
911 | } | |
912 | } | |
3acd9eb3 | 913 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 914 | } |
a858af28 PM |
915 | |
916 | /* | |
917 | * Now rat on any tasks that got kicked up to the root rcu_node | |
918 | * due to CPU offlining. | |
919 | */ | |
920 | rnp = rcu_get_root(rsp); | |
921 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
285fe294 | 922 | ndetected += rcu_print_task_stall(rnp); |
a858af28 PM |
923 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
924 | ||
925 | print_cpu_stall_info_end(); | |
926 | printk(KERN_CONT "(detected by %d, t=%ld jiffies)\n", | |
64db4cff | 927 | smp_processor_id(), (long)(jiffies - rsp->gp_start)); |
9bc8b558 PM |
928 | if (ndetected == 0) |
929 | printk(KERN_ERR "INFO: Stall ended before state dump start\n"); | |
930 | else if (!trigger_all_cpu_backtrace()) | |
4627e240 | 931 | dump_stack(); |
c1dc0b9c | 932 | |
4cdfc175 | 933 | /* Complain about tasks blocking the grace period. */ |
1ed509a2 PM |
934 | |
935 | rcu_print_detail_task_stall(rsp); | |
936 | ||
4cdfc175 | 937 | force_quiescent_state(rsp); /* Kick them all. */ |
64db4cff PM |
938 | } |
939 | ||
940 | static void print_cpu_stall(struct rcu_state *rsp) | |
941 | { | |
942 | unsigned long flags; | |
943 | struct rcu_node *rnp = rcu_get_root(rsp); | |
944 | ||
8cdd32a9 PM |
945 | /* |
946 | * OK, time to rat on ourselves... | |
947 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
948 | * RCU CPU stall warnings. | |
949 | */ | |
a858af28 PM |
950 | printk(KERN_ERR "INFO: %s self-detected stall on CPU", rsp->name); |
951 | print_cpu_stall_info_begin(); | |
952 | print_cpu_stall_info(rsp, smp_processor_id()); | |
953 | print_cpu_stall_info_end(); | |
954 | printk(KERN_CONT " (t=%lu jiffies)\n", jiffies - rsp->gp_start); | |
4627e240 PM |
955 | if (!trigger_all_cpu_backtrace()) |
956 | dump_stack(); | |
c1dc0b9c | 957 | |
1304afb2 | 958 | raw_spin_lock_irqsave(&rnp->lock, flags); |
20133cfc | 959 | if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall)) |
13cfcca0 PM |
960 | rsp->jiffies_stall = jiffies + |
961 | 3 * jiffies_till_stall_check() + 3; | |
1304afb2 | 962 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
c1dc0b9c | 963 | |
64db4cff PM |
964 | set_need_resched(); /* kick ourselves to get things going. */ |
965 | } | |
966 | ||
967 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) | |
968 | { | |
bad6e139 PM |
969 | unsigned long j; |
970 | unsigned long js; | |
64db4cff PM |
971 | struct rcu_node *rnp; |
972 | ||
742734ee | 973 | if (rcu_cpu_stall_suppress) |
c68de209 | 974 | return; |
bad6e139 PM |
975 | j = ACCESS_ONCE(jiffies); |
976 | js = ACCESS_ONCE(rsp->jiffies_stall); | |
64db4cff | 977 | rnp = rdp->mynode; |
c96ea7cf PM |
978 | if (rcu_gp_in_progress(rsp) && |
979 | (ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) { | |
64db4cff PM |
980 | |
981 | /* We haven't checked in, so go dump stack. */ | |
982 | print_cpu_stall(rsp); | |
983 | ||
bad6e139 PM |
984 | } else if (rcu_gp_in_progress(rsp) && |
985 | ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) { | |
64db4cff | 986 | |
bad6e139 | 987 | /* They had a few time units to dump stack, so complain. */ |
64db4cff PM |
988 | print_other_cpu_stall(rsp); |
989 | } | |
990 | } | |
991 | ||
c68de209 PM |
992 | static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr) |
993 | { | |
742734ee | 994 | rcu_cpu_stall_suppress = 1; |
c68de209 PM |
995 | return NOTIFY_DONE; |
996 | } | |
997 | ||
53d84e00 PM |
998 | /** |
999 | * rcu_cpu_stall_reset - prevent further stall warnings in current grace period | |
1000 | * | |
1001 | * Set the stall-warning timeout way off into the future, thus preventing | |
1002 | * any RCU CPU stall-warning messages from appearing in the current set of | |
1003 | * RCU grace periods. | |
1004 | * | |
1005 | * The caller must disable hard irqs. | |
1006 | */ | |
1007 | void rcu_cpu_stall_reset(void) | |
1008 | { | |
6ce75a23 PM |
1009 | struct rcu_state *rsp; |
1010 | ||
1011 | for_each_rcu_flavor(rsp) | |
1012 | rsp->jiffies_stall = jiffies + ULONG_MAX / 2; | |
53d84e00 PM |
1013 | } |
1014 | ||
c68de209 PM |
1015 | static struct notifier_block rcu_panic_block = { |
1016 | .notifier_call = rcu_panic, | |
1017 | }; | |
1018 | ||
1019 | static void __init check_cpu_stall_init(void) | |
1020 | { | |
1021 | atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block); | |
1022 | } | |
1023 | ||
64db4cff PM |
1024 | /* |
1025 | * Update CPU-local rcu_data state to record the newly noticed grace period. | |
1026 | * This is used both when we started the grace period and when we notice | |
9160306e PM |
1027 | * that someone else started the grace period. The caller must hold the |
1028 | * ->lock of the leaf rcu_node structure corresponding to the current CPU, | |
1029 | * and must have irqs disabled. | |
64db4cff | 1030 | */ |
9160306e PM |
1031 | static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
1032 | { | |
1033 | if (rdp->gpnum != rnp->gpnum) { | |
121dfc4b PM |
1034 | /* |
1035 | * If the current grace period is waiting for this CPU, | |
1036 | * set up to detect a quiescent state, otherwise don't | |
1037 | * go looking for one. | |
1038 | */ | |
9160306e | 1039 | rdp->gpnum = rnp->gpnum; |
d4c08f2a | 1040 | trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpustart"); |
d7d6a11e PM |
1041 | rdp->passed_quiesce = 0; |
1042 | rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask); | |
a858af28 | 1043 | zero_cpu_stall_ticks(rdp); |
9160306e PM |
1044 | } |
1045 | } | |
1046 | ||
64db4cff PM |
1047 | static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) |
1048 | { | |
9160306e PM |
1049 | unsigned long flags; |
1050 | struct rcu_node *rnp; | |
1051 | ||
1052 | local_irq_save(flags); | |
1053 | rnp = rdp->mynode; | |
1054 | if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */ | |
1304afb2 | 1055 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
9160306e PM |
1056 | local_irq_restore(flags); |
1057 | return; | |
1058 | } | |
1059 | __note_new_gpnum(rsp, rnp, rdp); | |
1304afb2 | 1060 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1061 | } |
1062 | ||
1063 | /* | |
1064 | * Did someone else start a new RCU grace period start since we last | |
1065 | * checked? Update local state appropriately if so. Must be called | |
1066 | * on the CPU corresponding to rdp. | |
1067 | */ | |
1068 | static int | |
1069 | check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp) | |
1070 | { | |
1071 | unsigned long flags; | |
1072 | int ret = 0; | |
1073 | ||
1074 | local_irq_save(flags); | |
1075 | if (rdp->gpnum != rsp->gpnum) { | |
1076 | note_new_gpnum(rsp, rdp); | |
1077 | ret = 1; | |
1078 | } | |
1079 | local_irq_restore(flags); | |
1080 | return ret; | |
1081 | } | |
1082 | ||
3f5d3ea6 PM |
1083 | /* |
1084 | * Initialize the specified rcu_data structure's callback list to empty. | |
1085 | */ | |
1086 | static void init_callback_list(struct rcu_data *rdp) | |
1087 | { | |
1088 | int i; | |
1089 | ||
1090 | rdp->nxtlist = NULL; | |
1091 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
1092 | rdp->nxttail[i] = &rdp->nxtlist; | |
1093 | } | |
1094 | ||
d09b62df PM |
1095 | /* |
1096 | * Advance this CPU's callbacks, but only if the current grace period | |
1097 | * has ended. This may be called only from the CPU to whom the rdp | |
1098 | * belongs. In addition, the corresponding leaf rcu_node structure's | |
1099 | * ->lock must be held by the caller, with irqs disabled. | |
1100 | */ | |
1101 | static void | |
1102 | __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) | |
1103 | { | |
1104 | /* Did another grace period end? */ | |
1105 | if (rdp->completed != rnp->completed) { | |
1106 | ||
1107 | /* Advance callbacks. No harm if list empty. */ | |
1108 | rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL]; | |
1109 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL]; | |
1110 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
1111 | ||
1112 | /* Remember that we saw this grace-period completion. */ | |
1113 | rdp->completed = rnp->completed; | |
d4c08f2a | 1114 | trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuend"); |
20377f32 | 1115 | |
5ff8e6f0 FW |
1116 | /* |
1117 | * If we were in an extended quiescent state, we may have | |
121dfc4b | 1118 | * missed some grace periods that others CPUs handled on |
5ff8e6f0 | 1119 | * our behalf. Catch up with this state to avoid noting |
121dfc4b PM |
1120 | * spurious new grace periods. If another grace period |
1121 | * has started, then rnp->gpnum will have advanced, so | |
d7d6a11e PM |
1122 | * we will detect this later on. Of course, any quiescent |
1123 | * states we found for the old GP are now invalid. | |
5ff8e6f0 | 1124 | */ |
d7d6a11e | 1125 | if (ULONG_CMP_LT(rdp->gpnum, rdp->completed)) { |
5ff8e6f0 | 1126 | rdp->gpnum = rdp->completed; |
d7d6a11e PM |
1127 | rdp->passed_quiesce = 0; |
1128 | } | |
5ff8e6f0 | 1129 | |
20377f32 | 1130 | /* |
121dfc4b PM |
1131 | * If RCU does not need a quiescent state from this CPU, |
1132 | * then make sure that this CPU doesn't go looking for one. | |
20377f32 | 1133 | */ |
121dfc4b | 1134 | if ((rnp->qsmask & rdp->grpmask) == 0) |
20377f32 | 1135 | rdp->qs_pending = 0; |
d09b62df PM |
1136 | } |
1137 | } | |
1138 | ||
1139 | /* | |
1140 | * Advance this CPU's callbacks, but only if the current grace period | |
1141 | * has ended. This may be called only from the CPU to whom the rdp | |
1142 | * belongs. | |
1143 | */ | |
1144 | static void | |
1145 | rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) | |
1146 | { | |
1147 | unsigned long flags; | |
1148 | struct rcu_node *rnp; | |
1149 | ||
1150 | local_irq_save(flags); | |
1151 | rnp = rdp->mynode; | |
1152 | if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */ | |
1304afb2 | 1153 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
d09b62df PM |
1154 | local_irq_restore(flags); |
1155 | return; | |
1156 | } | |
1157 | __rcu_process_gp_end(rsp, rnp, rdp); | |
1304afb2 | 1158 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
d09b62df PM |
1159 | } |
1160 | ||
1161 | /* | |
1162 | * Do per-CPU grace-period initialization for running CPU. The caller | |
1163 | * must hold the lock of the leaf rcu_node structure corresponding to | |
1164 | * this CPU. | |
1165 | */ | |
1166 | static void | |
1167 | rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) | |
1168 | { | |
1169 | /* Prior grace period ended, so advance callbacks for current CPU. */ | |
1170 | __rcu_process_gp_end(rsp, rnp, rdp); | |
1171 | ||
9160306e PM |
1172 | /* Set state so that this CPU will detect the next quiescent state. */ |
1173 | __note_new_gpnum(rsp, rnp, rdp); | |
d09b62df PM |
1174 | } |
1175 | ||
b3dbec76 | 1176 | /* |
7fdefc10 | 1177 | * Initialize a new grace period. |
b3dbec76 | 1178 | */ |
7fdefc10 | 1179 | static int rcu_gp_init(struct rcu_state *rsp) |
b3dbec76 PM |
1180 | { |
1181 | struct rcu_data *rdp; | |
7fdefc10 | 1182 | struct rcu_node *rnp = rcu_get_root(rsp); |
b3dbec76 | 1183 | |
7fdefc10 | 1184 | raw_spin_lock_irq(&rnp->lock); |
4cdfc175 | 1185 | rsp->gp_flags = 0; /* Clear all flags: New grace period. */ |
b3dbec76 | 1186 | |
7fdefc10 PM |
1187 | if (rcu_gp_in_progress(rsp)) { |
1188 | /* Grace period already in progress, don't start another. */ | |
1189 | raw_spin_unlock_irq(&rnp->lock); | |
1190 | return 0; | |
1191 | } | |
1192 | ||
7fdefc10 PM |
1193 | /* Advance to a new grace period and initialize state. */ |
1194 | rsp->gpnum++; | |
1195 | trace_rcu_grace_period(rsp->name, rsp->gpnum, "start"); | |
7fdefc10 PM |
1196 | record_gp_stall_check_time(rsp); |
1197 | raw_spin_unlock_irq(&rnp->lock); | |
1198 | ||
1199 | /* Exclude any concurrent CPU-hotplug operations. */ | |
1200 | get_online_cpus(); | |
1201 | ||
1202 | /* | |
1203 | * Set the quiescent-state-needed bits in all the rcu_node | |
1204 | * structures for all currently online CPUs in breadth-first order, | |
1205 | * starting from the root rcu_node structure, relying on the layout | |
1206 | * of the tree within the rsp->node[] array. Note that other CPUs | |
1207 | * will access only the leaves of the hierarchy, thus seeing that no | |
1208 | * grace period is in progress, at least until the corresponding | |
1209 | * leaf node has been initialized. In addition, we have excluded | |
1210 | * CPU-hotplug operations. | |
1211 | * | |
1212 | * The grace period cannot complete until the initialization | |
1213 | * process finishes, because this kthread handles both. | |
1214 | */ | |
1215 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
b3dbec76 | 1216 | raw_spin_lock_irq(&rnp->lock); |
b3dbec76 | 1217 | rdp = this_cpu_ptr(rsp->rda); |
7fdefc10 PM |
1218 | rcu_preempt_check_blocked_tasks(rnp); |
1219 | rnp->qsmask = rnp->qsmaskinit; | |
1220 | rnp->gpnum = rsp->gpnum; | |
25d30cf4 | 1221 | WARN_ON_ONCE(rnp->completed != rsp->completed); |
7fdefc10 PM |
1222 | rnp->completed = rsp->completed; |
1223 | if (rnp == rdp->mynode) | |
1224 | rcu_start_gp_per_cpu(rsp, rnp, rdp); | |
1225 | rcu_preempt_boost_start_gp(rnp); | |
1226 | trace_rcu_grace_period_init(rsp->name, rnp->gpnum, | |
1227 | rnp->level, rnp->grplo, | |
1228 | rnp->grphi, rnp->qsmask); | |
1229 | raw_spin_unlock_irq(&rnp->lock); | |
661a85dc PM |
1230 | #ifdef CONFIG_PROVE_RCU_DELAY |
1231 | if ((random32() % (rcu_num_nodes * 8)) == 0) | |
1232 | schedule_timeout_uninterruptible(2); | |
1233 | #endif /* #ifdef CONFIG_PROVE_RCU_DELAY */ | |
7fdefc10 PM |
1234 | cond_resched(); |
1235 | } | |
b3dbec76 | 1236 | |
7fdefc10 PM |
1237 | put_online_cpus(); |
1238 | return 1; | |
1239 | } | |
b3dbec76 | 1240 | |
4cdfc175 PM |
1241 | /* |
1242 | * Do one round of quiescent-state forcing. | |
1243 | */ | |
1244 | int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in) | |
1245 | { | |
1246 | int fqs_state = fqs_state_in; | |
1247 | struct rcu_node *rnp = rcu_get_root(rsp); | |
1248 | ||
1249 | rsp->n_force_qs++; | |
1250 | if (fqs_state == RCU_SAVE_DYNTICK) { | |
1251 | /* Collect dyntick-idle snapshots. */ | |
1252 | force_qs_rnp(rsp, dyntick_save_progress_counter); | |
1253 | fqs_state = RCU_FORCE_QS; | |
1254 | } else { | |
1255 | /* Handle dyntick-idle and offline CPUs. */ | |
1256 | force_qs_rnp(rsp, rcu_implicit_dynticks_qs); | |
1257 | } | |
1258 | /* Clear flag to prevent immediate re-entry. */ | |
1259 | if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { | |
1260 | raw_spin_lock_irq(&rnp->lock); | |
1261 | rsp->gp_flags &= ~RCU_GP_FLAG_FQS; | |
1262 | raw_spin_unlock_irq(&rnp->lock); | |
1263 | } | |
1264 | return fqs_state; | |
1265 | } | |
1266 | ||
7fdefc10 PM |
1267 | /* |
1268 | * Clean up after the old grace period. | |
1269 | */ | |
4cdfc175 | 1270 | static void rcu_gp_cleanup(struct rcu_state *rsp) |
7fdefc10 PM |
1271 | { |
1272 | unsigned long gp_duration; | |
1273 | struct rcu_data *rdp; | |
1274 | struct rcu_node *rnp = rcu_get_root(rsp); | |
b3dbec76 | 1275 | |
7fdefc10 PM |
1276 | raw_spin_lock_irq(&rnp->lock); |
1277 | gp_duration = jiffies - rsp->gp_start; | |
1278 | if (gp_duration > rsp->gp_max) | |
1279 | rsp->gp_max = gp_duration; | |
b3dbec76 | 1280 | |
7fdefc10 PM |
1281 | /* |
1282 | * We know the grace period is complete, but to everyone else | |
1283 | * it appears to still be ongoing. But it is also the case | |
1284 | * that to everyone else it looks like there is nothing that | |
1285 | * they can do to advance the grace period. It is therefore | |
1286 | * safe for us to drop the lock in order to mark the grace | |
1287 | * period as completed in all of the rcu_node structures. | |
7fdefc10 | 1288 | */ |
5d4b8659 | 1289 | raw_spin_unlock_irq(&rnp->lock); |
b3dbec76 | 1290 | |
5d4b8659 PM |
1291 | /* |
1292 | * Propagate new ->completed value to rcu_node structures so | |
1293 | * that other CPUs don't have to wait until the start of the next | |
1294 | * grace period to process their callbacks. This also avoids | |
1295 | * some nasty RCU grace-period initialization races by forcing | |
1296 | * the end of the current grace period to be completely recorded in | |
1297 | * all of the rcu_node structures before the beginning of the next | |
1298 | * grace period is recorded in any of the rcu_node structures. | |
1299 | */ | |
1300 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
755609a9 | 1301 | raw_spin_lock_irq(&rnp->lock); |
5d4b8659 PM |
1302 | rnp->completed = rsp->gpnum; |
1303 | raw_spin_unlock_irq(&rnp->lock); | |
1304 | cond_resched(); | |
7fdefc10 | 1305 | } |
5d4b8659 PM |
1306 | rnp = rcu_get_root(rsp); |
1307 | raw_spin_lock_irq(&rnp->lock); | |
7fdefc10 PM |
1308 | |
1309 | rsp->completed = rsp->gpnum; /* Declare grace period done. */ | |
1310 | trace_rcu_grace_period(rsp->name, rsp->completed, "end"); | |
1311 | rsp->fqs_state = RCU_GP_IDLE; | |
5d4b8659 | 1312 | rdp = this_cpu_ptr(rsp->rda); |
7fdefc10 PM |
1313 | if (cpu_needs_another_gp(rsp, rdp)) |
1314 | rsp->gp_flags = 1; | |
1315 | raw_spin_unlock_irq(&rnp->lock); | |
7fdefc10 PM |
1316 | } |
1317 | ||
1318 | /* | |
1319 | * Body of kthread that handles grace periods. | |
1320 | */ | |
1321 | static int __noreturn rcu_gp_kthread(void *arg) | |
1322 | { | |
4cdfc175 | 1323 | int fqs_state; |
d40011f6 | 1324 | unsigned long j; |
4cdfc175 | 1325 | int ret; |
7fdefc10 PM |
1326 | struct rcu_state *rsp = arg; |
1327 | struct rcu_node *rnp = rcu_get_root(rsp); | |
1328 | ||
1329 | for (;;) { | |
1330 | ||
1331 | /* Handle grace-period start. */ | |
1332 | for (;;) { | |
4cdfc175 PM |
1333 | wait_event_interruptible(rsp->gp_wq, |
1334 | rsp->gp_flags & | |
1335 | RCU_GP_FLAG_INIT); | |
1336 | if ((rsp->gp_flags & RCU_GP_FLAG_INIT) && | |
1337 | rcu_gp_init(rsp)) | |
7fdefc10 PM |
1338 | break; |
1339 | cond_resched(); | |
1340 | flush_signals(current); | |
1341 | } | |
cabc49c1 | 1342 | |
4cdfc175 PM |
1343 | /* Handle quiescent-state forcing. */ |
1344 | fqs_state = RCU_SAVE_DYNTICK; | |
d40011f6 PM |
1345 | j = jiffies_till_first_fqs; |
1346 | if (j > HZ) { | |
1347 | j = HZ; | |
1348 | jiffies_till_first_fqs = HZ; | |
1349 | } | |
cabc49c1 | 1350 | for (;;) { |
d40011f6 | 1351 | rsp->jiffies_force_qs = jiffies + j; |
4cdfc175 PM |
1352 | ret = wait_event_interruptible_timeout(rsp->gp_wq, |
1353 | (rsp->gp_flags & RCU_GP_FLAG_FQS) || | |
1354 | (!ACCESS_ONCE(rnp->qsmask) && | |
1355 | !rcu_preempt_blocked_readers_cgp(rnp)), | |
d40011f6 | 1356 | j); |
4cdfc175 | 1357 | /* If grace period done, leave loop. */ |
cabc49c1 | 1358 | if (!ACCESS_ONCE(rnp->qsmask) && |
4cdfc175 | 1359 | !rcu_preempt_blocked_readers_cgp(rnp)) |
cabc49c1 | 1360 | break; |
4cdfc175 PM |
1361 | /* If time for quiescent-state forcing, do it. */ |
1362 | if (ret == 0 || (rsp->gp_flags & RCU_GP_FLAG_FQS)) { | |
1363 | fqs_state = rcu_gp_fqs(rsp, fqs_state); | |
1364 | cond_resched(); | |
1365 | } else { | |
1366 | /* Deal with stray signal. */ | |
1367 | cond_resched(); | |
1368 | flush_signals(current); | |
1369 | } | |
d40011f6 PM |
1370 | j = jiffies_till_next_fqs; |
1371 | if (j > HZ) { | |
1372 | j = HZ; | |
1373 | jiffies_till_next_fqs = HZ; | |
1374 | } else if (j < 1) { | |
1375 | j = 1; | |
1376 | jiffies_till_next_fqs = 1; | |
1377 | } | |
cabc49c1 | 1378 | } |
4cdfc175 PM |
1379 | |
1380 | /* Handle grace-period end. */ | |
1381 | rcu_gp_cleanup(rsp); | |
b3dbec76 | 1382 | } |
b3dbec76 PM |
1383 | } |
1384 | ||
64db4cff PM |
1385 | /* |
1386 | * Start a new RCU grace period if warranted, re-initializing the hierarchy | |
1387 | * in preparation for detecting the next grace period. The caller must hold | |
1388 | * the root node's ->lock, which is released before return. Hard irqs must | |
1389 | * be disabled. | |
e5601400 PM |
1390 | * |
1391 | * Note that it is legal for a dying CPU (which is marked as offline) to | |
1392 | * invoke this function. This can happen when the dying CPU reports its | |
1393 | * quiescent state. | |
64db4cff PM |
1394 | */ |
1395 | static void | |
1396 | rcu_start_gp(struct rcu_state *rsp, unsigned long flags) | |
1397 | __releases(rcu_get_root(rsp)->lock) | |
1398 | { | |
394f99a9 | 1399 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); |
64db4cff | 1400 | struct rcu_node *rnp = rcu_get_root(rsp); |
64db4cff | 1401 | |
b3dbec76 | 1402 | if (!rsp->gp_kthread || |
afe24b12 PM |
1403 | !cpu_needs_another_gp(rsp, rdp)) { |
1404 | /* | |
b3dbec76 PM |
1405 | * Either we have not yet spawned the grace-period |
1406 | * task or this CPU does not need another grace period. | |
1407 | * Either way, don't start a new grace period. | |
afe24b12 PM |
1408 | */ |
1409 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
1410 | return; | |
1411 | } | |
b32e9eb6 | 1412 | |
4cdfc175 | 1413 | rsp->gp_flags = RCU_GP_FLAG_INIT; |
b3dbec76 PM |
1414 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1415 | wake_up(&rsp->gp_wq); | |
64db4cff PM |
1416 | } |
1417 | ||
f41d911f | 1418 | /* |
d3f6bad3 PM |
1419 | * Report a full set of quiescent states to the specified rcu_state |
1420 | * data structure. This involves cleaning up after the prior grace | |
1421 | * period and letting rcu_start_gp() start up the next grace period | |
1422 | * if one is needed. Note that the caller must hold rnp->lock, as | |
1423 | * required by rcu_start_gp(), which will release it. | |
f41d911f | 1424 | */ |
d3f6bad3 | 1425 | static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) |
fc2219d4 | 1426 | __releases(rcu_get_root(rsp)->lock) |
f41d911f | 1427 | { |
fc2219d4 | 1428 | WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
cabc49c1 PM |
1429 | raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags); |
1430 | wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */ | |
f41d911f PM |
1431 | } |
1432 | ||
64db4cff | 1433 | /* |
d3f6bad3 PM |
1434 | * Similar to rcu_report_qs_rdp(), for which it is a helper function. |
1435 | * Allows quiescent states for a group of CPUs to be reported at one go | |
1436 | * to the specified rcu_node structure, though all the CPUs in the group | |
1437 | * must be represented by the same rcu_node structure (which need not be | |
1438 | * a leaf rcu_node structure, though it often will be). That structure's | |
1439 | * lock must be held upon entry, and it is released before return. | |
64db4cff PM |
1440 | */ |
1441 | static void | |
d3f6bad3 PM |
1442 | rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, |
1443 | struct rcu_node *rnp, unsigned long flags) | |
64db4cff PM |
1444 | __releases(rnp->lock) |
1445 | { | |
28ecd580 PM |
1446 | struct rcu_node *rnp_c; |
1447 | ||
64db4cff PM |
1448 | /* Walk up the rcu_node hierarchy. */ |
1449 | for (;;) { | |
1450 | if (!(rnp->qsmask & mask)) { | |
1451 | ||
1452 | /* Our bit has already been cleared, so done. */ | |
1304afb2 | 1453 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1454 | return; |
1455 | } | |
1456 | rnp->qsmask &= ~mask; | |
d4c08f2a PM |
1457 | trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum, |
1458 | mask, rnp->qsmask, rnp->level, | |
1459 | rnp->grplo, rnp->grphi, | |
1460 | !!rnp->gp_tasks); | |
27f4d280 | 1461 | if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { |
64db4cff PM |
1462 | |
1463 | /* Other bits still set at this level, so done. */ | |
1304afb2 | 1464 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1465 | return; |
1466 | } | |
1467 | mask = rnp->grpmask; | |
1468 | if (rnp->parent == NULL) { | |
1469 | ||
1470 | /* No more levels. Exit loop holding root lock. */ | |
1471 | ||
1472 | break; | |
1473 | } | |
1304afb2 | 1474 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
28ecd580 | 1475 | rnp_c = rnp; |
64db4cff | 1476 | rnp = rnp->parent; |
1304afb2 | 1477 | raw_spin_lock_irqsave(&rnp->lock, flags); |
28ecd580 | 1478 | WARN_ON_ONCE(rnp_c->qsmask); |
64db4cff PM |
1479 | } |
1480 | ||
1481 | /* | |
1482 | * Get here if we are the last CPU to pass through a quiescent | |
d3f6bad3 | 1483 | * state for this grace period. Invoke rcu_report_qs_rsp() |
f41d911f | 1484 | * to clean up and start the next grace period if one is needed. |
64db4cff | 1485 | */ |
d3f6bad3 | 1486 | rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ |
64db4cff PM |
1487 | } |
1488 | ||
1489 | /* | |
d3f6bad3 PM |
1490 | * Record a quiescent state for the specified CPU to that CPU's rcu_data |
1491 | * structure. This must be either called from the specified CPU, or | |
1492 | * called when the specified CPU is known to be offline (and when it is | |
1493 | * also known that no other CPU is concurrently trying to help the offline | |
1494 | * CPU). The lastcomp argument is used to make sure we are still in the | |
1495 | * grace period of interest. We don't want to end the current grace period | |
1496 | * based on quiescent states detected in an earlier grace period! | |
64db4cff PM |
1497 | */ |
1498 | static void | |
d7d6a11e | 1499 | rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) |
64db4cff PM |
1500 | { |
1501 | unsigned long flags; | |
1502 | unsigned long mask; | |
1503 | struct rcu_node *rnp; | |
1504 | ||
1505 | rnp = rdp->mynode; | |
1304afb2 | 1506 | raw_spin_lock_irqsave(&rnp->lock, flags); |
d7d6a11e PM |
1507 | if (rdp->passed_quiesce == 0 || rdp->gpnum != rnp->gpnum || |
1508 | rnp->completed == rnp->gpnum) { | |
64db4cff PM |
1509 | |
1510 | /* | |
e4cc1f22 PM |
1511 | * The grace period in which this quiescent state was |
1512 | * recorded has ended, so don't report it upwards. | |
1513 | * We will instead need a new quiescent state that lies | |
1514 | * within the current grace period. | |
64db4cff | 1515 | */ |
e4cc1f22 | 1516 | rdp->passed_quiesce = 0; /* need qs for new gp. */ |
1304afb2 | 1517 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1518 | return; |
1519 | } | |
1520 | mask = rdp->grpmask; | |
1521 | if ((rnp->qsmask & mask) == 0) { | |
1304afb2 | 1522 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1523 | } else { |
1524 | rdp->qs_pending = 0; | |
1525 | ||
1526 | /* | |
1527 | * This GP can't end until cpu checks in, so all of our | |
1528 | * callbacks can be processed during the next GP. | |
1529 | */ | |
64db4cff PM |
1530 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
1531 | ||
d3f6bad3 | 1532 | rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */ |
64db4cff PM |
1533 | } |
1534 | } | |
1535 | ||
1536 | /* | |
1537 | * Check to see if there is a new grace period of which this CPU | |
1538 | * is not yet aware, and if so, set up local rcu_data state for it. | |
1539 | * Otherwise, see if this CPU has just passed through its first | |
1540 | * quiescent state for this grace period, and record that fact if so. | |
1541 | */ | |
1542 | static void | |
1543 | rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) | |
1544 | { | |
1545 | /* If there is now a new grace period, record and return. */ | |
1546 | if (check_for_new_grace_period(rsp, rdp)) | |
1547 | return; | |
1548 | ||
1549 | /* | |
1550 | * Does this CPU still need to do its part for current grace period? | |
1551 | * If no, return and let the other CPUs do their part as well. | |
1552 | */ | |
1553 | if (!rdp->qs_pending) | |
1554 | return; | |
1555 | ||
1556 | /* | |
1557 | * Was there a quiescent state since the beginning of the grace | |
1558 | * period? If no, then exit and wait for the next call. | |
1559 | */ | |
e4cc1f22 | 1560 | if (!rdp->passed_quiesce) |
64db4cff PM |
1561 | return; |
1562 | ||
d3f6bad3 PM |
1563 | /* |
1564 | * Tell RCU we are done (but rcu_report_qs_rdp() will be the | |
1565 | * judge of that). | |
1566 | */ | |
d7d6a11e | 1567 | rcu_report_qs_rdp(rdp->cpu, rsp, rdp); |
64db4cff PM |
1568 | } |
1569 | ||
1570 | #ifdef CONFIG_HOTPLUG_CPU | |
1571 | ||
e74f4c45 | 1572 | /* |
b1420f1c PM |
1573 | * Send the specified CPU's RCU callbacks to the orphanage. The |
1574 | * specified CPU must be offline, and the caller must hold the | |
1575 | * ->onofflock. | |
e74f4c45 | 1576 | */ |
b1420f1c PM |
1577 | static void |
1578 | rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp, | |
1579 | struct rcu_node *rnp, struct rcu_data *rdp) | |
e74f4c45 | 1580 | { |
b1420f1c PM |
1581 | /* |
1582 | * Orphan the callbacks. First adjust the counts. This is safe | |
1583 | * because ->onofflock excludes _rcu_barrier()'s adoption of | |
1584 | * the callbacks, thus no memory barrier is required. | |
1585 | */ | |
a50c3af9 | 1586 | if (rdp->nxtlist != NULL) { |
b1420f1c PM |
1587 | rsp->qlen_lazy += rdp->qlen_lazy; |
1588 | rsp->qlen += rdp->qlen; | |
1589 | rdp->n_cbs_orphaned += rdp->qlen; | |
a50c3af9 | 1590 | rdp->qlen_lazy = 0; |
1d1fb395 | 1591 | ACCESS_ONCE(rdp->qlen) = 0; |
a50c3af9 PM |
1592 | } |
1593 | ||
1594 | /* | |
b1420f1c PM |
1595 | * Next, move those callbacks still needing a grace period to |
1596 | * the orphanage, where some other CPU will pick them up. | |
1597 | * Some of the callbacks might have gone partway through a grace | |
1598 | * period, but that is too bad. They get to start over because we | |
1599 | * cannot assume that grace periods are synchronized across CPUs. | |
1600 | * We don't bother updating the ->nxttail[] array yet, instead | |
1601 | * we just reset the whole thing later on. | |
a50c3af9 | 1602 | */ |
b1420f1c PM |
1603 | if (*rdp->nxttail[RCU_DONE_TAIL] != NULL) { |
1604 | *rsp->orphan_nxttail = *rdp->nxttail[RCU_DONE_TAIL]; | |
1605 | rsp->orphan_nxttail = rdp->nxttail[RCU_NEXT_TAIL]; | |
1606 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
a50c3af9 PM |
1607 | } |
1608 | ||
1609 | /* | |
b1420f1c PM |
1610 | * Then move the ready-to-invoke callbacks to the orphanage, |
1611 | * where some other CPU will pick them up. These will not be | |
1612 | * required to pass though another grace period: They are done. | |
a50c3af9 | 1613 | */ |
e5601400 | 1614 | if (rdp->nxtlist != NULL) { |
b1420f1c PM |
1615 | *rsp->orphan_donetail = rdp->nxtlist; |
1616 | rsp->orphan_donetail = rdp->nxttail[RCU_DONE_TAIL]; | |
e5601400 | 1617 | } |
e74f4c45 | 1618 | |
b1420f1c | 1619 | /* Finally, initialize the rcu_data structure's list to empty. */ |
3f5d3ea6 | 1620 | init_callback_list(rdp); |
b1420f1c PM |
1621 | } |
1622 | ||
1623 | /* | |
1624 | * Adopt the RCU callbacks from the specified rcu_state structure's | |
1625 | * orphanage. The caller must hold the ->onofflock. | |
1626 | */ | |
1627 | static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) | |
1628 | { | |
1629 | int i; | |
1630 | struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); | |
1631 | ||
b1420f1c PM |
1632 | /* Do the accounting first. */ |
1633 | rdp->qlen_lazy += rsp->qlen_lazy; | |
1634 | rdp->qlen += rsp->qlen; | |
1635 | rdp->n_cbs_adopted += rsp->qlen; | |
8f5af6f1 PM |
1636 | if (rsp->qlen_lazy != rsp->qlen) |
1637 | rcu_idle_count_callbacks_posted(); | |
b1420f1c PM |
1638 | rsp->qlen_lazy = 0; |
1639 | rsp->qlen = 0; | |
1640 | ||
1641 | /* | |
1642 | * We do not need a memory barrier here because the only way we | |
1643 | * can get here if there is an rcu_barrier() in flight is if | |
1644 | * we are the task doing the rcu_barrier(). | |
1645 | */ | |
1646 | ||
1647 | /* First adopt the ready-to-invoke callbacks. */ | |
1648 | if (rsp->orphan_donelist != NULL) { | |
1649 | *rsp->orphan_donetail = *rdp->nxttail[RCU_DONE_TAIL]; | |
1650 | *rdp->nxttail[RCU_DONE_TAIL] = rsp->orphan_donelist; | |
1651 | for (i = RCU_NEXT_SIZE - 1; i >= RCU_DONE_TAIL; i--) | |
1652 | if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) | |
1653 | rdp->nxttail[i] = rsp->orphan_donetail; | |
1654 | rsp->orphan_donelist = NULL; | |
1655 | rsp->orphan_donetail = &rsp->orphan_donelist; | |
1656 | } | |
1657 | ||
1658 | /* And then adopt the callbacks that still need a grace period. */ | |
1659 | if (rsp->orphan_nxtlist != NULL) { | |
1660 | *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxtlist; | |
1661 | rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxttail; | |
1662 | rsp->orphan_nxtlist = NULL; | |
1663 | rsp->orphan_nxttail = &rsp->orphan_nxtlist; | |
1664 | } | |
1665 | } | |
1666 | ||
1667 | /* | |
1668 | * Trace the fact that this CPU is going offline. | |
1669 | */ | |
1670 | static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) | |
1671 | { | |
1672 | RCU_TRACE(unsigned long mask); | |
1673 | RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda)); | |
1674 | RCU_TRACE(struct rcu_node *rnp = rdp->mynode); | |
1675 | ||
1676 | RCU_TRACE(mask = rdp->grpmask); | |
e5601400 PM |
1677 | trace_rcu_grace_period(rsp->name, |
1678 | rnp->gpnum + 1 - !!(rnp->qsmask & mask), | |
1679 | "cpuofl"); | |
64db4cff PM |
1680 | } |
1681 | ||
1682 | /* | |
e5601400 | 1683 | * The CPU has been completely removed, and some other CPU is reporting |
b1420f1c PM |
1684 | * this fact from process context. Do the remainder of the cleanup, |
1685 | * including orphaning the outgoing CPU's RCU callbacks, and also | |
1331e7a1 PM |
1686 | * adopting them. There can only be one CPU hotplug operation at a time, |
1687 | * so no other CPU can be attempting to update rcu_cpu_kthread_task. | |
64db4cff | 1688 | */ |
e5601400 | 1689 | static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) |
64db4cff | 1690 | { |
2036d94a PM |
1691 | unsigned long flags; |
1692 | unsigned long mask; | |
1693 | int need_report = 0; | |
e5601400 | 1694 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
b1420f1c | 1695 | struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ |
e5601400 | 1696 | |
2036d94a | 1697 | /* Adjust any no-longer-needed kthreads. */ |
5d01bbd1 | 1698 | rcu_boost_kthread_setaffinity(rnp, -1); |
2036d94a | 1699 | |
b1420f1c | 1700 | /* Remove the dead CPU from the bitmasks in the rcu_node hierarchy. */ |
2036d94a PM |
1701 | |
1702 | /* Exclude any attempts to start a new grace period. */ | |
1703 | raw_spin_lock_irqsave(&rsp->onofflock, flags); | |
1704 | ||
b1420f1c PM |
1705 | /* Orphan the dead CPU's callbacks, and adopt them if appropriate. */ |
1706 | rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp); | |
1707 | rcu_adopt_orphan_cbs(rsp); | |
1708 | ||
2036d94a PM |
1709 | /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ |
1710 | mask = rdp->grpmask; /* rnp->grplo is constant. */ | |
1711 | do { | |
1712 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ | |
1713 | rnp->qsmaskinit &= ~mask; | |
1714 | if (rnp->qsmaskinit != 0) { | |
1715 | if (rnp != rdp->mynode) | |
1716 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
1717 | break; | |
1718 | } | |
1719 | if (rnp == rdp->mynode) | |
1720 | need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp); | |
1721 | else | |
1722 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
1723 | mask = rnp->grpmask; | |
1724 | rnp = rnp->parent; | |
1725 | } while (rnp != NULL); | |
1726 | ||
1727 | /* | |
1728 | * We still hold the leaf rcu_node structure lock here, and | |
1729 | * irqs are still disabled. The reason for this subterfuge is | |
1730 | * because invoking rcu_report_unblock_qs_rnp() with ->onofflock | |
1731 | * held leads to deadlock. | |
1732 | */ | |
1733 | raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ | |
1734 | rnp = rdp->mynode; | |
1735 | if (need_report & RCU_OFL_TASKS_NORM_GP) | |
1736 | rcu_report_unblock_qs_rnp(rnp, flags); | |
1737 | else | |
1738 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
1739 | if (need_report & RCU_OFL_TASKS_EXP_GP) | |
1740 | rcu_report_exp_rnp(rsp, rnp, true); | |
cf01537e PM |
1741 | WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL, |
1742 | "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n", | |
1743 | cpu, rdp->qlen, rdp->nxtlist); | |
0d8ee37e PM |
1744 | init_callback_list(rdp); |
1745 | /* Disallow further callbacks on this CPU. */ | |
1746 | rdp->nxttail[RCU_NEXT_TAIL] = NULL; | |
64db4cff PM |
1747 | } |
1748 | ||
1749 | #else /* #ifdef CONFIG_HOTPLUG_CPU */ | |
1750 | ||
e5601400 | 1751 | static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) |
e74f4c45 PM |
1752 | { |
1753 | } | |
1754 | ||
e5601400 | 1755 | static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) |
64db4cff PM |
1756 | { |
1757 | } | |
1758 | ||
1759 | #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ | |
1760 | ||
1761 | /* | |
1762 | * Invoke any RCU callbacks that have made it to the end of their grace | |
1763 | * period. Thottle as specified by rdp->blimit. | |
1764 | */ | |
37c72e56 | 1765 | static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) |
64db4cff PM |
1766 | { |
1767 | unsigned long flags; | |
1768 | struct rcu_head *next, *list, **tail; | |
b41772ab | 1769 | int bl, count, count_lazy, i; |
64db4cff PM |
1770 | |
1771 | /* If no callbacks are ready, just return.*/ | |
29c00b4a | 1772 | if (!cpu_has_callbacks_ready_to_invoke(rdp)) { |
486e2593 | 1773 | trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0); |
4968c300 PM |
1774 | trace_rcu_batch_end(rsp->name, 0, !!ACCESS_ONCE(rdp->nxtlist), |
1775 | need_resched(), is_idle_task(current), | |
1776 | rcu_is_callbacks_kthread()); | |
64db4cff | 1777 | return; |
29c00b4a | 1778 | } |
64db4cff PM |
1779 | |
1780 | /* | |
1781 | * Extract the list of ready callbacks, disabling to prevent | |
1782 | * races with call_rcu() from interrupt handlers. | |
1783 | */ | |
1784 | local_irq_save(flags); | |
8146c4e2 | 1785 | WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); |
29c00b4a | 1786 | bl = rdp->blimit; |
486e2593 | 1787 | trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl); |
64db4cff PM |
1788 | list = rdp->nxtlist; |
1789 | rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; | |
1790 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
1791 | tail = rdp->nxttail[RCU_DONE_TAIL]; | |
b41772ab PM |
1792 | for (i = RCU_NEXT_SIZE - 1; i >= 0; i--) |
1793 | if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) | |
1794 | rdp->nxttail[i] = &rdp->nxtlist; | |
64db4cff PM |
1795 | local_irq_restore(flags); |
1796 | ||
1797 | /* Invoke callbacks. */ | |
486e2593 | 1798 | count = count_lazy = 0; |
64db4cff PM |
1799 | while (list) { |
1800 | next = list->next; | |
1801 | prefetch(next); | |
551d55a9 | 1802 | debug_rcu_head_unqueue(list); |
486e2593 PM |
1803 | if (__rcu_reclaim(rsp->name, list)) |
1804 | count_lazy++; | |
64db4cff | 1805 | list = next; |
dff1672d PM |
1806 | /* Stop only if limit reached and CPU has something to do. */ |
1807 | if (++count >= bl && | |
1808 | (need_resched() || | |
1809 | (!is_idle_task(current) && !rcu_is_callbacks_kthread()))) | |
64db4cff PM |
1810 | break; |
1811 | } | |
1812 | ||
1813 | local_irq_save(flags); | |
4968c300 PM |
1814 | trace_rcu_batch_end(rsp->name, count, !!list, need_resched(), |
1815 | is_idle_task(current), | |
1816 | rcu_is_callbacks_kthread()); | |
64db4cff PM |
1817 | |
1818 | /* Update count, and requeue any remaining callbacks. */ | |
64db4cff PM |
1819 | if (list != NULL) { |
1820 | *tail = rdp->nxtlist; | |
1821 | rdp->nxtlist = list; | |
b41772ab PM |
1822 | for (i = 0; i < RCU_NEXT_SIZE; i++) |
1823 | if (&rdp->nxtlist == rdp->nxttail[i]) | |
1824 | rdp->nxttail[i] = tail; | |
64db4cff PM |
1825 | else |
1826 | break; | |
1827 | } | |
b1420f1c PM |
1828 | smp_mb(); /* List handling before counting for rcu_barrier(). */ |
1829 | rdp->qlen_lazy -= count_lazy; | |
1d1fb395 | 1830 | ACCESS_ONCE(rdp->qlen) -= count; |
b1420f1c | 1831 | rdp->n_cbs_invoked += count; |
64db4cff PM |
1832 | |
1833 | /* Reinstate batch limit if we have worked down the excess. */ | |
1834 | if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) | |
1835 | rdp->blimit = blimit; | |
1836 | ||
37c72e56 PM |
1837 | /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
1838 | if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { | |
1839 | rdp->qlen_last_fqs_check = 0; | |
1840 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
1841 | } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) | |
1842 | rdp->qlen_last_fqs_check = rdp->qlen; | |
cfca9279 | 1843 | WARN_ON_ONCE((rdp->nxtlist == NULL) != (rdp->qlen == 0)); |
37c72e56 | 1844 | |
64db4cff PM |
1845 | local_irq_restore(flags); |
1846 | ||
e0f23060 | 1847 | /* Re-invoke RCU core processing if there are callbacks remaining. */ |
64db4cff | 1848 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
a46e0899 | 1849 | invoke_rcu_core(); |
64db4cff PM |
1850 | } |
1851 | ||
1852 | /* | |
1853 | * Check to see if this CPU is in a non-context-switch quiescent state | |
1854 | * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). | |
e0f23060 | 1855 | * Also schedule RCU core processing. |
64db4cff | 1856 | * |
9b2e4f18 | 1857 | * This function must be called from hardirq context. It is normally |
64db4cff PM |
1858 | * invoked from the scheduling-clock interrupt. If rcu_pending returns |
1859 | * false, there is no point in invoking rcu_check_callbacks(). | |
1860 | */ | |
1861 | void rcu_check_callbacks(int cpu, int user) | |
1862 | { | |
300df91c | 1863 | trace_rcu_utilization("Start scheduler-tick"); |
a858af28 | 1864 | increment_cpu_stall_ticks(); |
9b2e4f18 | 1865 | if (user || rcu_is_cpu_rrupt_from_idle()) { |
64db4cff PM |
1866 | |
1867 | /* | |
1868 | * Get here if this CPU took its interrupt from user | |
1869 | * mode or from the idle loop, and if this is not a | |
1870 | * nested interrupt. In this case, the CPU is in | |
d6714c22 | 1871 | * a quiescent state, so note it. |
64db4cff PM |
1872 | * |
1873 | * No memory barrier is required here because both | |
d6714c22 PM |
1874 | * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
1875 | * variables that other CPUs neither access nor modify, | |
1876 | * at least not while the corresponding CPU is online. | |
64db4cff PM |
1877 | */ |
1878 | ||
d6714c22 PM |
1879 | rcu_sched_qs(cpu); |
1880 | rcu_bh_qs(cpu); | |
64db4cff PM |
1881 | |
1882 | } else if (!in_softirq()) { | |
1883 | ||
1884 | /* | |
1885 | * Get here if this CPU did not take its interrupt from | |
1886 | * softirq, in other words, if it is not interrupting | |
1887 | * a rcu_bh read-side critical section. This is an _bh | |
d6714c22 | 1888 | * critical section, so note it. |
64db4cff PM |
1889 | */ |
1890 | ||
d6714c22 | 1891 | rcu_bh_qs(cpu); |
64db4cff | 1892 | } |
f41d911f | 1893 | rcu_preempt_check_callbacks(cpu); |
d21670ac | 1894 | if (rcu_pending(cpu)) |
a46e0899 | 1895 | invoke_rcu_core(); |
300df91c | 1896 | trace_rcu_utilization("End scheduler-tick"); |
64db4cff PM |
1897 | } |
1898 | ||
64db4cff PM |
1899 | /* |
1900 | * Scan the leaf rcu_node structures, processing dyntick state for any that | |
1901 | * have not yet encountered a quiescent state, using the function specified. | |
27f4d280 PM |
1902 | * Also initiate boosting for any threads blocked on the root rcu_node. |
1903 | * | |
ee47eb9f | 1904 | * The caller must have suppressed start of new grace periods. |
64db4cff | 1905 | */ |
45f014c5 | 1906 | static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)) |
64db4cff PM |
1907 | { |
1908 | unsigned long bit; | |
1909 | int cpu; | |
1910 | unsigned long flags; | |
1911 | unsigned long mask; | |
a0b6c9a7 | 1912 | struct rcu_node *rnp; |
64db4cff | 1913 | |
a0b6c9a7 | 1914 | rcu_for_each_leaf_node(rsp, rnp) { |
b4be093f | 1915 | cond_resched(); |
64db4cff | 1916 | mask = 0; |
1304afb2 | 1917 | raw_spin_lock_irqsave(&rnp->lock, flags); |
ee47eb9f | 1918 | if (!rcu_gp_in_progress(rsp)) { |
1304afb2 | 1919 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
0f10dc82 | 1920 | return; |
64db4cff | 1921 | } |
a0b6c9a7 | 1922 | if (rnp->qsmask == 0) { |
1217ed1b | 1923 | rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ |
64db4cff PM |
1924 | continue; |
1925 | } | |
a0b6c9a7 | 1926 | cpu = rnp->grplo; |
64db4cff | 1927 | bit = 1; |
a0b6c9a7 | 1928 | for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { |
394f99a9 LJ |
1929 | if ((rnp->qsmask & bit) != 0 && |
1930 | f(per_cpu_ptr(rsp->rda, cpu))) | |
64db4cff PM |
1931 | mask |= bit; |
1932 | } | |
45f014c5 | 1933 | if (mask != 0) { |
64db4cff | 1934 | |
d3f6bad3 PM |
1935 | /* rcu_report_qs_rnp() releases rnp->lock. */ |
1936 | rcu_report_qs_rnp(mask, rsp, rnp, flags); | |
64db4cff PM |
1937 | continue; |
1938 | } | |
1304afb2 | 1939 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 1940 | } |
27f4d280 | 1941 | rnp = rcu_get_root(rsp); |
1217ed1b PM |
1942 | if (rnp->qsmask == 0) { |
1943 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
1944 | rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */ | |
1945 | } | |
64db4cff PM |
1946 | } |
1947 | ||
1948 | /* | |
1949 | * Force quiescent states on reluctant CPUs, and also detect which | |
1950 | * CPUs are in dyntick-idle mode. | |
1951 | */ | |
4cdfc175 | 1952 | static void force_quiescent_state(struct rcu_state *rsp) |
64db4cff PM |
1953 | { |
1954 | unsigned long flags; | |
394f2769 PM |
1955 | bool ret; |
1956 | struct rcu_node *rnp; | |
1957 | struct rcu_node *rnp_old = NULL; | |
1958 | ||
1959 | /* Funnel through hierarchy to reduce memory contention. */ | |
1960 | rnp = per_cpu_ptr(rsp->rda, raw_smp_processor_id())->mynode; | |
1961 | for (; rnp != NULL; rnp = rnp->parent) { | |
1962 | ret = (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) || | |
1963 | !raw_spin_trylock(&rnp->fqslock); | |
1964 | if (rnp_old != NULL) | |
1965 | raw_spin_unlock(&rnp_old->fqslock); | |
1966 | if (ret) { | |
1967 | rsp->n_force_qs_lh++; | |
1968 | return; | |
1969 | } | |
1970 | rnp_old = rnp; | |
1971 | } | |
1972 | /* rnp_old == rcu_get_root(rsp), rnp == NULL. */ | |
64db4cff | 1973 | |
394f2769 PM |
1974 | /* Reached the root of the rcu_node tree, acquire lock. */ |
1975 | raw_spin_lock_irqsave(&rnp_old->lock, flags); | |
1976 | raw_spin_unlock(&rnp_old->fqslock); | |
1977 | if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { | |
1978 | rsp->n_force_qs_lh++; | |
1979 | raw_spin_unlock_irqrestore(&rnp_old->lock, flags); | |
4cdfc175 | 1980 | return; /* Someone beat us to it. */ |
46a1e34e | 1981 | } |
4cdfc175 | 1982 | rsp->gp_flags |= RCU_GP_FLAG_FQS; |
394f2769 | 1983 | raw_spin_unlock_irqrestore(&rnp_old->lock, flags); |
4cdfc175 | 1984 | wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */ |
64db4cff PM |
1985 | } |
1986 | ||
64db4cff | 1987 | /* |
e0f23060 PM |
1988 | * This does the RCU core processing work for the specified rcu_state |
1989 | * and rcu_data structures. This may be called only from the CPU to | |
1990 | * whom the rdp belongs. | |
64db4cff PM |
1991 | */ |
1992 | static void | |
1bca8cf1 | 1993 | __rcu_process_callbacks(struct rcu_state *rsp) |
64db4cff PM |
1994 | { |
1995 | unsigned long flags; | |
1bca8cf1 | 1996 | struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); |
64db4cff | 1997 | |
2e597558 PM |
1998 | WARN_ON_ONCE(rdp->beenonline == 0); |
1999 | ||
64db4cff PM |
2000 | /* |
2001 | * Advance callbacks in response to end of earlier grace | |
2002 | * period that some other CPU ended. | |
2003 | */ | |
2004 | rcu_process_gp_end(rsp, rdp); | |
2005 | ||
2006 | /* Update RCU state based on any recent quiescent states. */ | |
2007 | rcu_check_quiescent_state(rsp, rdp); | |
2008 | ||
2009 | /* Does this CPU require a not-yet-started grace period? */ | |
2010 | if (cpu_needs_another_gp(rsp, rdp)) { | |
1304afb2 | 2011 | raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags); |
64db4cff PM |
2012 | rcu_start_gp(rsp, flags); /* releases above lock */ |
2013 | } | |
2014 | ||
2015 | /* If there are callbacks ready, invoke them. */ | |
09223371 | 2016 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
a46e0899 | 2017 | invoke_rcu_callbacks(rsp, rdp); |
09223371 SL |
2018 | } |
2019 | ||
64db4cff | 2020 | /* |
e0f23060 | 2021 | * Do RCU core processing for the current CPU. |
64db4cff | 2022 | */ |
09223371 | 2023 | static void rcu_process_callbacks(struct softirq_action *unused) |
64db4cff | 2024 | { |
6ce75a23 PM |
2025 | struct rcu_state *rsp; |
2026 | ||
bfa00b4c PM |
2027 | if (cpu_is_offline(smp_processor_id())) |
2028 | return; | |
300df91c | 2029 | trace_rcu_utilization("Start RCU core"); |
6ce75a23 PM |
2030 | for_each_rcu_flavor(rsp) |
2031 | __rcu_process_callbacks(rsp); | |
300df91c | 2032 | trace_rcu_utilization("End RCU core"); |
64db4cff PM |
2033 | } |
2034 | ||
a26ac245 | 2035 | /* |
e0f23060 PM |
2036 | * Schedule RCU callback invocation. If the specified type of RCU |
2037 | * does not support RCU priority boosting, just do a direct call, | |
2038 | * otherwise wake up the per-CPU kernel kthread. Note that because we | |
2039 | * are running on the current CPU with interrupts disabled, the | |
2040 | * rcu_cpu_kthread_task cannot disappear out from under us. | |
a26ac245 | 2041 | */ |
a46e0899 | 2042 | static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) |
a26ac245 | 2043 | { |
b0d30417 PM |
2044 | if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active))) |
2045 | return; | |
a46e0899 PM |
2046 | if (likely(!rsp->boost)) { |
2047 | rcu_do_batch(rsp, rdp); | |
a26ac245 PM |
2048 | return; |
2049 | } | |
a46e0899 | 2050 | invoke_rcu_callbacks_kthread(); |
a26ac245 PM |
2051 | } |
2052 | ||
a46e0899 | 2053 | static void invoke_rcu_core(void) |
09223371 SL |
2054 | { |
2055 | raise_softirq(RCU_SOFTIRQ); | |
2056 | } | |
2057 | ||
29154c57 PM |
2058 | /* |
2059 | * Handle any core-RCU processing required by a call_rcu() invocation. | |
2060 | */ | |
2061 | static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp, | |
2062 | struct rcu_head *head, unsigned long flags) | |
64db4cff | 2063 | { |
62fde6ed PM |
2064 | /* |
2065 | * If called from an extended quiescent state, invoke the RCU | |
2066 | * core in order to force a re-evaluation of RCU's idleness. | |
2067 | */ | |
a16b7a69 | 2068 | if (rcu_is_cpu_idle() && cpu_online(smp_processor_id())) |
62fde6ed PM |
2069 | invoke_rcu_core(); |
2070 | ||
a16b7a69 | 2071 | /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ |
29154c57 | 2072 | if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) |
2655d57e | 2073 | return; |
64db4cff | 2074 | |
37c72e56 PM |
2075 | /* |
2076 | * Force the grace period if too many callbacks or too long waiting. | |
2077 | * Enforce hysteresis, and don't invoke force_quiescent_state() | |
2078 | * if some other CPU has recently done so. Also, don't bother | |
2079 | * invoking force_quiescent_state() if the newly enqueued callback | |
2080 | * is the only one waiting for a grace period to complete. | |
2081 | */ | |
2655d57e | 2082 | if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { |
b52573d2 PM |
2083 | |
2084 | /* Are we ignoring a completed grace period? */ | |
2085 | rcu_process_gp_end(rsp, rdp); | |
2086 | check_for_new_grace_period(rsp, rdp); | |
2087 | ||
2088 | /* Start a new grace period if one not already started. */ | |
2089 | if (!rcu_gp_in_progress(rsp)) { | |
2090 | unsigned long nestflag; | |
2091 | struct rcu_node *rnp_root = rcu_get_root(rsp); | |
2092 | ||
2093 | raw_spin_lock_irqsave(&rnp_root->lock, nestflag); | |
2094 | rcu_start_gp(rsp, nestflag); /* rlses rnp_root->lock */ | |
2095 | } else { | |
2096 | /* Give the grace period a kick. */ | |
2097 | rdp->blimit = LONG_MAX; | |
2098 | if (rsp->n_force_qs == rdp->n_force_qs_snap && | |
2099 | *rdp->nxttail[RCU_DONE_TAIL] != head) | |
4cdfc175 | 2100 | force_quiescent_state(rsp); |
b52573d2 PM |
2101 | rdp->n_force_qs_snap = rsp->n_force_qs; |
2102 | rdp->qlen_last_fqs_check = rdp->qlen; | |
2103 | } | |
4cdfc175 | 2104 | } |
29154c57 PM |
2105 | } |
2106 | ||
64db4cff PM |
2107 | static void |
2108 | __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), | |
486e2593 | 2109 | struct rcu_state *rsp, bool lazy) |
64db4cff PM |
2110 | { |
2111 | unsigned long flags; | |
2112 | struct rcu_data *rdp; | |
2113 | ||
0bb7b59d | 2114 | WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */ |
551d55a9 | 2115 | debug_rcu_head_queue(head); |
64db4cff PM |
2116 | head->func = func; |
2117 | head->next = NULL; | |
2118 | ||
64db4cff PM |
2119 | /* |
2120 | * Opportunistically note grace-period endings and beginnings. | |
2121 | * Note that we might see a beginning right after we see an | |
2122 | * end, but never vice versa, since this CPU has to pass through | |
2123 | * a quiescent state betweentimes. | |
2124 | */ | |
2125 | local_irq_save(flags); | |
394f99a9 | 2126 | rdp = this_cpu_ptr(rsp->rda); |
64db4cff PM |
2127 | |
2128 | /* Add the callback to our list. */ | |
0d8ee37e PM |
2129 | if (unlikely(rdp->nxttail[RCU_NEXT_TAIL] == NULL)) { |
2130 | /* _call_rcu() is illegal on offline CPU; leak the callback. */ | |
2131 | WARN_ON_ONCE(1); | |
2132 | local_irq_restore(flags); | |
2133 | return; | |
2134 | } | |
29154c57 | 2135 | ACCESS_ONCE(rdp->qlen)++; |
486e2593 PM |
2136 | if (lazy) |
2137 | rdp->qlen_lazy++; | |
c57afe80 PM |
2138 | else |
2139 | rcu_idle_count_callbacks_posted(); | |
b1420f1c PM |
2140 | smp_mb(); /* Count before adding callback for rcu_barrier(). */ |
2141 | *rdp->nxttail[RCU_NEXT_TAIL] = head; | |
2142 | rdp->nxttail[RCU_NEXT_TAIL] = &head->next; | |
2655d57e | 2143 | |
d4c08f2a PM |
2144 | if (__is_kfree_rcu_offset((unsigned long)func)) |
2145 | trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func, | |
486e2593 | 2146 | rdp->qlen_lazy, rdp->qlen); |
d4c08f2a | 2147 | else |
486e2593 | 2148 | trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen); |
d4c08f2a | 2149 | |
29154c57 PM |
2150 | /* Go handle any RCU core processing required. */ |
2151 | __call_rcu_core(rsp, rdp, head, flags); | |
64db4cff PM |
2152 | local_irq_restore(flags); |
2153 | } | |
2154 | ||
2155 | /* | |
d6714c22 | 2156 | * Queue an RCU-sched callback for invocation after a grace period. |
64db4cff | 2157 | */ |
d6714c22 | 2158 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
64db4cff | 2159 | { |
486e2593 | 2160 | __call_rcu(head, func, &rcu_sched_state, 0); |
64db4cff | 2161 | } |
d6714c22 | 2162 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
64db4cff PM |
2163 | |
2164 | /* | |
486e2593 | 2165 | * Queue an RCU callback for invocation after a quicker grace period. |
64db4cff PM |
2166 | */ |
2167 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
2168 | { | |
486e2593 | 2169 | __call_rcu(head, func, &rcu_bh_state, 0); |
64db4cff PM |
2170 | } |
2171 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
2172 | ||
6d813391 PM |
2173 | /* |
2174 | * Because a context switch is a grace period for RCU-sched and RCU-bh, | |
2175 | * any blocking grace-period wait automatically implies a grace period | |
2176 | * if there is only one CPU online at any point time during execution | |
2177 | * of either synchronize_sched() or synchronize_rcu_bh(). It is OK to | |
2178 | * occasionally incorrectly indicate that there are multiple CPUs online | |
2179 | * when there was in fact only one the whole time, as this just adds | |
2180 | * some overhead: RCU still operates correctly. | |
6d813391 PM |
2181 | */ |
2182 | static inline int rcu_blocking_is_gp(void) | |
2183 | { | |
95f0c1de PM |
2184 | int ret; |
2185 | ||
6d813391 | 2186 | might_sleep(); /* Check for RCU read-side critical section. */ |
95f0c1de PM |
2187 | preempt_disable(); |
2188 | ret = num_online_cpus() <= 1; | |
2189 | preempt_enable(); | |
2190 | return ret; | |
6d813391 PM |
2191 | } |
2192 | ||
6ebb237b PM |
2193 | /** |
2194 | * synchronize_sched - wait until an rcu-sched grace period has elapsed. | |
2195 | * | |
2196 | * Control will return to the caller some time after a full rcu-sched | |
2197 | * grace period has elapsed, in other words after all currently executing | |
2198 | * rcu-sched read-side critical sections have completed. These read-side | |
2199 | * critical sections are delimited by rcu_read_lock_sched() and | |
2200 | * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), | |
2201 | * local_irq_disable(), and so on may be used in place of | |
2202 | * rcu_read_lock_sched(). | |
2203 | * | |
2204 | * This means that all preempt_disable code sequences, including NMI and | |
2205 | * hardware-interrupt handlers, in progress on entry will have completed | |
2206 | * before this primitive returns. However, this does not guarantee that | |
2207 | * softirq handlers will have completed, since in some kernels, these | |
2208 | * handlers can run in process context, and can block. | |
2209 | * | |
2210 | * This primitive provides the guarantees made by the (now removed) | |
2211 | * synchronize_kernel() API. In contrast, synchronize_rcu() only | |
2212 | * guarantees that rcu_read_lock() sections will have completed. | |
2213 | * In "classic RCU", these two guarantees happen to be one and | |
2214 | * the same, but can differ in realtime RCU implementations. | |
2215 | */ | |
2216 | void synchronize_sched(void) | |
2217 | { | |
fe15d706 PM |
2218 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
2219 | !lock_is_held(&rcu_lock_map) && | |
2220 | !lock_is_held(&rcu_sched_lock_map), | |
2221 | "Illegal synchronize_sched() in RCU-sched read-side critical section"); | |
6ebb237b PM |
2222 | if (rcu_blocking_is_gp()) |
2223 | return; | |
2c42818e | 2224 | wait_rcu_gp(call_rcu_sched); |
6ebb237b PM |
2225 | } |
2226 | EXPORT_SYMBOL_GPL(synchronize_sched); | |
2227 | ||
2228 | /** | |
2229 | * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. | |
2230 | * | |
2231 | * Control will return to the caller some time after a full rcu_bh grace | |
2232 | * period has elapsed, in other words after all currently executing rcu_bh | |
2233 | * read-side critical sections have completed. RCU read-side critical | |
2234 | * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), | |
2235 | * and may be nested. | |
2236 | */ | |
2237 | void synchronize_rcu_bh(void) | |
2238 | { | |
fe15d706 PM |
2239 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
2240 | !lock_is_held(&rcu_lock_map) && | |
2241 | !lock_is_held(&rcu_sched_lock_map), | |
2242 | "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section"); | |
6ebb237b PM |
2243 | if (rcu_blocking_is_gp()) |
2244 | return; | |
2c42818e | 2245 | wait_rcu_gp(call_rcu_bh); |
6ebb237b PM |
2246 | } |
2247 | EXPORT_SYMBOL_GPL(synchronize_rcu_bh); | |
2248 | ||
3d3b7db0 PM |
2249 | static atomic_t sync_sched_expedited_started = ATOMIC_INIT(0); |
2250 | static atomic_t sync_sched_expedited_done = ATOMIC_INIT(0); | |
2251 | ||
2252 | static int synchronize_sched_expedited_cpu_stop(void *data) | |
2253 | { | |
2254 | /* | |
2255 | * There must be a full memory barrier on each affected CPU | |
2256 | * between the time that try_stop_cpus() is called and the | |
2257 | * time that it returns. | |
2258 | * | |
2259 | * In the current initial implementation of cpu_stop, the | |
2260 | * above condition is already met when the control reaches | |
2261 | * this point and the following smp_mb() is not strictly | |
2262 | * necessary. Do smp_mb() anyway for documentation and | |
2263 | * robustness against future implementation changes. | |
2264 | */ | |
2265 | smp_mb(); /* See above comment block. */ | |
2266 | return 0; | |
2267 | } | |
2268 | ||
236fefaf PM |
2269 | /** |
2270 | * synchronize_sched_expedited - Brute-force RCU-sched grace period | |
2271 | * | |
2272 | * Wait for an RCU-sched grace period to elapse, but use a "big hammer" | |
2273 | * approach to force the grace period to end quickly. This consumes | |
2274 | * significant time on all CPUs and is unfriendly to real-time workloads, | |
2275 | * so is thus not recommended for any sort of common-case code. In fact, | |
2276 | * if you are using synchronize_sched_expedited() in a loop, please | |
2277 | * restructure your code to batch your updates, and then use a single | |
2278 | * synchronize_sched() instead. | |
3d3b7db0 | 2279 | * |
236fefaf PM |
2280 | * Note that it is illegal to call this function while holding any lock |
2281 | * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal | |
2282 | * to call this function from a CPU-hotplug notifier. Failing to observe | |
2283 | * these restriction will result in deadlock. | |
3d3b7db0 PM |
2284 | * |
2285 | * This implementation can be thought of as an application of ticket | |
2286 | * locking to RCU, with sync_sched_expedited_started and | |
2287 | * sync_sched_expedited_done taking on the roles of the halves | |
2288 | * of the ticket-lock word. Each task atomically increments | |
2289 | * sync_sched_expedited_started upon entry, snapshotting the old value, | |
2290 | * then attempts to stop all the CPUs. If this succeeds, then each | |
2291 | * CPU will have executed a context switch, resulting in an RCU-sched | |
2292 | * grace period. We are then done, so we use atomic_cmpxchg() to | |
2293 | * update sync_sched_expedited_done to match our snapshot -- but | |
2294 | * only if someone else has not already advanced past our snapshot. | |
2295 | * | |
2296 | * On the other hand, if try_stop_cpus() fails, we check the value | |
2297 | * of sync_sched_expedited_done. If it has advanced past our | |
2298 | * initial snapshot, then someone else must have forced a grace period | |
2299 | * some time after we took our snapshot. In this case, our work is | |
2300 | * done for us, and we can simply return. Otherwise, we try again, | |
2301 | * but keep our initial snapshot for purposes of checking for someone | |
2302 | * doing our work for us. | |
2303 | * | |
2304 | * If we fail too many times in a row, we fall back to synchronize_sched(). | |
2305 | */ | |
2306 | void synchronize_sched_expedited(void) | |
2307 | { | |
2308 | int firstsnap, s, snap, trycount = 0; | |
2309 | ||
2310 | /* Note that atomic_inc_return() implies full memory barrier. */ | |
2311 | firstsnap = snap = atomic_inc_return(&sync_sched_expedited_started); | |
2312 | get_online_cpus(); | |
1cc85961 | 2313 | WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id())); |
3d3b7db0 PM |
2314 | |
2315 | /* | |
2316 | * Each pass through the following loop attempts to force a | |
2317 | * context switch on each CPU. | |
2318 | */ | |
2319 | while (try_stop_cpus(cpu_online_mask, | |
2320 | synchronize_sched_expedited_cpu_stop, | |
2321 | NULL) == -EAGAIN) { | |
2322 | put_online_cpus(); | |
2323 | ||
2324 | /* No joy, try again later. Or just synchronize_sched(). */ | |
c701d5d9 | 2325 | if (trycount++ < 10) { |
3d3b7db0 | 2326 | udelay(trycount * num_online_cpus()); |
c701d5d9 | 2327 | } else { |
3d3b7db0 PM |
2328 | synchronize_sched(); |
2329 | return; | |
2330 | } | |
2331 | ||
2332 | /* Check to see if someone else did our work for us. */ | |
2333 | s = atomic_read(&sync_sched_expedited_done); | |
2334 | if (UINT_CMP_GE((unsigned)s, (unsigned)firstsnap)) { | |
2335 | smp_mb(); /* ensure test happens before caller kfree */ | |
2336 | return; | |
2337 | } | |
2338 | ||
2339 | /* | |
2340 | * Refetching sync_sched_expedited_started allows later | |
2341 | * callers to piggyback on our grace period. We subtract | |
2342 | * 1 to get the same token that the last incrementer got. | |
2343 | * We retry after they started, so our grace period works | |
2344 | * for them, and they started after our first try, so their | |
2345 | * grace period works for us. | |
2346 | */ | |
2347 | get_online_cpus(); | |
2348 | snap = atomic_read(&sync_sched_expedited_started); | |
2349 | smp_mb(); /* ensure read is before try_stop_cpus(). */ | |
2350 | } | |
2351 | ||
2352 | /* | |
2353 | * Everyone up to our most recent fetch is covered by our grace | |
2354 | * period. Update the counter, but only if our work is still | |
2355 | * relevant -- which it won't be if someone who started later | |
2356 | * than we did beat us to the punch. | |
2357 | */ | |
2358 | do { | |
2359 | s = atomic_read(&sync_sched_expedited_done); | |
2360 | if (UINT_CMP_GE((unsigned)s, (unsigned)snap)) { | |
2361 | smp_mb(); /* ensure test happens before caller kfree */ | |
2362 | break; | |
2363 | } | |
2364 | } while (atomic_cmpxchg(&sync_sched_expedited_done, s, snap) != s); | |
2365 | ||
2366 | put_online_cpus(); | |
2367 | } | |
2368 | EXPORT_SYMBOL_GPL(synchronize_sched_expedited); | |
2369 | ||
64db4cff PM |
2370 | /* |
2371 | * Check to see if there is any immediate RCU-related work to be done | |
2372 | * by the current CPU, for the specified type of RCU, returning 1 if so. | |
2373 | * The checks are in order of increasing expense: checks that can be | |
2374 | * carried out against CPU-local state are performed first. However, | |
2375 | * we must check for CPU stalls first, else we might not get a chance. | |
2376 | */ | |
2377 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) | |
2378 | { | |
2f51f988 PM |
2379 | struct rcu_node *rnp = rdp->mynode; |
2380 | ||
64db4cff PM |
2381 | rdp->n_rcu_pending++; |
2382 | ||
2383 | /* Check for CPU stalls, if enabled. */ | |
2384 | check_cpu_stall(rsp, rdp); | |
2385 | ||
2386 | /* Is the RCU core waiting for a quiescent state from this CPU? */ | |
5c51dd73 PM |
2387 | if (rcu_scheduler_fully_active && |
2388 | rdp->qs_pending && !rdp->passed_quiesce) { | |
d21670ac | 2389 | rdp->n_rp_qs_pending++; |
e4cc1f22 | 2390 | } else if (rdp->qs_pending && rdp->passed_quiesce) { |
d21670ac | 2391 | rdp->n_rp_report_qs++; |
64db4cff | 2392 | return 1; |
7ba5c840 | 2393 | } |
64db4cff PM |
2394 | |
2395 | /* Does this CPU have callbacks ready to invoke? */ | |
7ba5c840 PM |
2396 | if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
2397 | rdp->n_rp_cb_ready++; | |
64db4cff | 2398 | return 1; |
7ba5c840 | 2399 | } |
64db4cff PM |
2400 | |
2401 | /* Has RCU gone idle with this CPU needing another grace period? */ | |
7ba5c840 PM |
2402 | if (cpu_needs_another_gp(rsp, rdp)) { |
2403 | rdp->n_rp_cpu_needs_gp++; | |
64db4cff | 2404 | return 1; |
7ba5c840 | 2405 | } |
64db4cff PM |
2406 | |
2407 | /* Has another RCU grace period completed? */ | |
2f51f988 | 2408 | if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ |
7ba5c840 | 2409 | rdp->n_rp_gp_completed++; |
64db4cff | 2410 | return 1; |
7ba5c840 | 2411 | } |
64db4cff PM |
2412 | |
2413 | /* Has a new RCU grace period started? */ | |
2f51f988 | 2414 | if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */ |
7ba5c840 | 2415 | rdp->n_rp_gp_started++; |
64db4cff | 2416 | return 1; |
7ba5c840 | 2417 | } |
64db4cff | 2418 | |
64db4cff | 2419 | /* nothing to do */ |
7ba5c840 | 2420 | rdp->n_rp_need_nothing++; |
64db4cff PM |
2421 | return 0; |
2422 | } | |
2423 | ||
2424 | /* | |
2425 | * Check to see if there is any immediate RCU-related work to be done | |
2426 | * by the current CPU, returning 1 if so. This function is part of the | |
2427 | * RCU implementation; it is -not- an exported member of the RCU API. | |
2428 | */ | |
a157229c | 2429 | static int rcu_pending(int cpu) |
64db4cff | 2430 | { |
6ce75a23 PM |
2431 | struct rcu_state *rsp; |
2432 | ||
2433 | for_each_rcu_flavor(rsp) | |
2434 | if (__rcu_pending(rsp, per_cpu_ptr(rsp->rda, cpu))) | |
2435 | return 1; | |
2436 | return 0; | |
64db4cff PM |
2437 | } |
2438 | ||
2439 | /* | |
2440 | * Check to see if any future RCU-related work will need to be done | |
2441 | * by the current CPU, even if none need be done immediately, returning | |
8bd93a2c | 2442 | * 1 if so. |
64db4cff | 2443 | */ |
aea1b35e | 2444 | static int rcu_cpu_has_callbacks(int cpu) |
64db4cff | 2445 | { |
6ce75a23 PM |
2446 | struct rcu_state *rsp; |
2447 | ||
64db4cff | 2448 | /* RCU callbacks either ready or pending? */ |
6ce75a23 PM |
2449 | for_each_rcu_flavor(rsp) |
2450 | if (per_cpu_ptr(rsp->rda, cpu)->nxtlist) | |
2451 | return 1; | |
2452 | return 0; | |
64db4cff PM |
2453 | } |
2454 | ||
a83eff0a PM |
2455 | /* |
2456 | * Helper function for _rcu_barrier() tracing. If tracing is disabled, | |
2457 | * the compiler is expected to optimize this away. | |
2458 | */ | |
2459 | static void _rcu_barrier_trace(struct rcu_state *rsp, char *s, | |
2460 | int cpu, unsigned long done) | |
2461 | { | |
2462 | trace_rcu_barrier(rsp->name, s, cpu, | |
2463 | atomic_read(&rsp->barrier_cpu_count), done); | |
2464 | } | |
2465 | ||
b1420f1c PM |
2466 | /* |
2467 | * RCU callback function for _rcu_barrier(). If we are last, wake | |
2468 | * up the task executing _rcu_barrier(). | |
2469 | */ | |
24ebbca8 | 2470 | static void rcu_barrier_callback(struct rcu_head *rhp) |
d0ec774c | 2471 | { |
24ebbca8 PM |
2472 | struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head); |
2473 | struct rcu_state *rsp = rdp->rsp; | |
2474 | ||
a83eff0a PM |
2475 | if (atomic_dec_and_test(&rsp->barrier_cpu_count)) { |
2476 | _rcu_barrier_trace(rsp, "LastCB", -1, rsp->n_barrier_done); | |
7db74df8 | 2477 | complete(&rsp->barrier_completion); |
a83eff0a PM |
2478 | } else { |
2479 | _rcu_barrier_trace(rsp, "CB", -1, rsp->n_barrier_done); | |
2480 | } | |
d0ec774c PM |
2481 | } |
2482 | ||
2483 | /* | |
2484 | * Called with preemption disabled, and from cross-cpu IRQ context. | |
2485 | */ | |
2486 | static void rcu_barrier_func(void *type) | |
2487 | { | |
037b64ed | 2488 | struct rcu_state *rsp = type; |
06668efa | 2489 | struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); |
d0ec774c | 2490 | |
a83eff0a | 2491 | _rcu_barrier_trace(rsp, "IRQ", -1, rsp->n_barrier_done); |
24ebbca8 | 2492 | atomic_inc(&rsp->barrier_cpu_count); |
06668efa | 2493 | rsp->call(&rdp->barrier_head, rcu_barrier_callback); |
d0ec774c PM |
2494 | } |
2495 | ||
d0ec774c PM |
2496 | /* |
2497 | * Orchestrate the specified type of RCU barrier, waiting for all | |
2498 | * RCU callbacks of the specified type to complete. | |
2499 | */ | |
037b64ed | 2500 | static void _rcu_barrier(struct rcu_state *rsp) |
d0ec774c | 2501 | { |
b1420f1c | 2502 | int cpu; |
b1420f1c | 2503 | struct rcu_data *rdp; |
cf3a9c48 PM |
2504 | unsigned long snap = ACCESS_ONCE(rsp->n_barrier_done); |
2505 | unsigned long snap_done; | |
b1420f1c | 2506 | |
a83eff0a | 2507 | _rcu_barrier_trace(rsp, "Begin", -1, snap); |
b1420f1c | 2508 | |
e74f4c45 | 2509 | /* Take mutex to serialize concurrent rcu_barrier() requests. */ |
7be7f0be | 2510 | mutex_lock(&rsp->barrier_mutex); |
b1420f1c | 2511 | |
cf3a9c48 PM |
2512 | /* |
2513 | * Ensure that all prior references, including to ->n_barrier_done, | |
2514 | * are ordered before the _rcu_barrier() machinery. | |
2515 | */ | |
2516 | smp_mb(); /* See above block comment. */ | |
2517 | ||
2518 | /* | |
2519 | * Recheck ->n_barrier_done to see if others did our work for us. | |
2520 | * This means checking ->n_barrier_done for an even-to-odd-to-even | |
2521 | * transition. The "if" expression below therefore rounds the old | |
2522 | * value up to the next even number and adds two before comparing. | |
2523 | */ | |
2524 | snap_done = ACCESS_ONCE(rsp->n_barrier_done); | |
a83eff0a | 2525 | _rcu_barrier_trace(rsp, "Check", -1, snap_done); |
cf3a9c48 | 2526 | if (ULONG_CMP_GE(snap_done, ((snap + 1) & ~0x1) + 2)) { |
a83eff0a | 2527 | _rcu_barrier_trace(rsp, "EarlyExit", -1, snap_done); |
cf3a9c48 PM |
2528 | smp_mb(); /* caller's subsequent code after above check. */ |
2529 | mutex_unlock(&rsp->barrier_mutex); | |
2530 | return; | |
2531 | } | |
2532 | ||
2533 | /* | |
2534 | * Increment ->n_barrier_done to avoid duplicate work. Use | |
2535 | * ACCESS_ONCE() to prevent the compiler from speculating | |
2536 | * the increment to precede the early-exit check. | |
2537 | */ | |
2538 | ACCESS_ONCE(rsp->n_barrier_done)++; | |
2539 | WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 1); | |
a83eff0a | 2540 | _rcu_barrier_trace(rsp, "Inc1", -1, rsp->n_barrier_done); |
cf3a9c48 | 2541 | smp_mb(); /* Order ->n_barrier_done increment with below mechanism. */ |
b1420f1c | 2542 | |
d0ec774c | 2543 | /* |
b1420f1c PM |
2544 | * Initialize the count to one rather than to zero in order to |
2545 | * avoid a too-soon return to zero in case of a short grace period | |
1331e7a1 PM |
2546 | * (or preemption of this task). Exclude CPU-hotplug operations |
2547 | * to ensure that no offline CPU has callbacks queued. | |
d0ec774c | 2548 | */ |
7db74df8 | 2549 | init_completion(&rsp->barrier_completion); |
24ebbca8 | 2550 | atomic_set(&rsp->barrier_cpu_count, 1); |
1331e7a1 | 2551 | get_online_cpus(); |
b1420f1c PM |
2552 | |
2553 | /* | |
1331e7a1 PM |
2554 | * Force each CPU with callbacks to register a new callback. |
2555 | * When that callback is invoked, we will know that all of the | |
2556 | * corresponding CPU's preceding callbacks have been invoked. | |
b1420f1c | 2557 | */ |
1331e7a1 | 2558 | for_each_online_cpu(cpu) { |
b1420f1c | 2559 | rdp = per_cpu_ptr(rsp->rda, cpu); |
1331e7a1 | 2560 | if (ACCESS_ONCE(rdp->qlen)) { |
a83eff0a PM |
2561 | _rcu_barrier_trace(rsp, "OnlineQ", cpu, |
2562 | rsp->n_barrier_done); | |
037b64ed | 2563 | smp_call_function_single(cpu, rcu_barrier_func, rsp, 1); |
b1420f1c | 2564 | } else { |
a83eff0a PM |
2565 | _rcu_barrier_trace(rsp, "OnlineNQ", cpu, |
2566 | rsp->n_barrier_done); | |
b1420f1c PM |
2567 | } |
2568 | } | |
1331e7a1 | 2569 | put_online_cpus(); |
b1420f1c PM |
2570 | |
2571 | /* | |
2572 | * Now that we have an rcu_barrier_callback() callback on each | |
2573 | * CPU, and thus each counted, remove the initial count. | |
2574 | */ | |
24ebbca8 | 2575 | if (atomic_dec_and_test(&rsp->barrier_cpu_count)) |
7db74df8 | 2576 | complete(&rsp->barrier_completion); |
b1420f1c | 2577 | |
cf3a9c48 PM |
2578 | /* Increment ->n_barrier_done to prevent duplicate work. */ |
2579 | smp_mb(); /* Keep increment after above mechanism. */ | |
2580 | ACCESS_ONCE(rsp->n_barrier_done)++; | |
2581 | WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 0); | |
a83eff0a | 2582 | _rcu_barrier_trace(rsp, "Inc2", -1, rsp->n_barrier_done); |
cf3a9c48 PM |
2583 | smp_mb(); /* Keep increment before caller's subsequent code. */ |
2584 | ||
b1420f1c | 2585 | /* Wait for all rcu_barrier_callback() callbacks to be invoked. */ |
7db74df8 | 2586 | wait_for_completion(&rsp->barrier_completion); |
b1420f1c PM |
2587 | |
2588 | /* Other rcu_barrier() invocations can now safely proceed. */ | |
7be7f0be | 2589 | mutex_unlock(&rsp->barrier_mutex); |
d0ec774c | 2590 | } |
d0ec774c PM |
2591 | |
2592 | /** | |
2593 | * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. | |
2594 | */ | |
2595 | void rcu_barrier_bh(void) | |
2596 | { | |
037b64ed | 2597 | _rcu_barrier(&rcu_bh_state); |
d0ec774c PM |
2598 | } |
2599 | EXPORT_SYMBOL_GPL(rcu_barrier_bh); | |
2600 | ||
2601 | /** | |
2602 | * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. | |
2603 | */ | |
2604 | void rcu_barrier_sched(void) | |
2605 | { | |
037b64ed | 2606 | _rcu_barrier(&rcu_sched_state); |
d0ec774c PM |
2607 | } |
2608 | EXPORT_SYMBOL_GPL(rcu_barrier_sched); | |
2609 | ||
64db4cff | 2610 | /* |
27569620 | 2611 | * Do boot-time initialization of a CPU's per-CPU RCU data. |
64db4cff | 2612 | */ |
27569620 PM |
2613 | static void __init |
2614 | rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) | |
64db4cff PM |
2615 | { |
2616 | unsigned long flags; | |
394f99a9 | 2617 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
27569620 PM |
2618 | struct rcu_node *rnp = rcu_get_root(rsp); |
2619 | ||
2620 | /* Set up local state, ensuring consistent view of global state. */ | |
1304afb2 | 2621 | raw_spin_lock_irqsave(&rnp->lock, flags); |
27569620 | 2622 | rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); |
3f5d3ea6 | 2623 | init_callback_list(rdp); |
486e2593 | 2624 | rdp->qlen_lazy = 0; |
1d1fb395 | 2625 | ACCESS_ONCE(rdp->qlen) = 0; |
27569620 | 2626 | rdp->dynticks = &per_cpu(rcu_dynticks, cpu); |
29e37d81 | 2627 | WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE); |
9b2e4f18 | 2628 | WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1); |
c5d900bf FW |
2629 | #ifdef CONFIG_RCU_USER_QS |
2630 | WARN_ON_ONCE(rdp->dynticks->in_user); | |
2631 | #endif | |
27569620 | 2632 | rdp->cpu = cpu; |
d4c08f2a | 2633 | rdp->rsp = rsp; |
1304afb2 | 2634 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27569620 PM |
2635 | } |
2636 | ||
2637 | /* | |
2638 | * Initialize a CPU's per-CPU RCU data. Note that only one online or | |
2639 | * offline event can be happening at a given time. Note also that we | |
2640 | * can accept some slop in the rsp->completed access due to the fact | |
2641 | * that this CPU cannot possibly have any RCU callbacks in flight yet. | |
64db4cff | 2642 | */ |
e4fa4c97 | 2643 | static void __cpuinit |
6cc68793 | 2644 | rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) |
64db4cff PM |
2645 | { |
2646 | unsigned long flags; | |
64db4cff | 2647 | unsigned long mask; |
394f99a9 | 2648 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
64db4cff PM |
2649 | struct rcu_node *rnp = rcu_get_root(rsp); |
2650 | ||
2651 | /* Set up local state, ensuring consistent view of global state. */ | |
1304afb2 | 2652 | raw_spin_lock_irqsave(&rnp->lock, flags); |
64db4cff | 2653 | rdp->beenonline = 1; /* We have now been online. */ |
6cc68793 | 2654 | rdp->preemptible = preemptible; |
37c72e56 PM |
2655 | rdp->qlen_last_fqs_check = 0; |
2656 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
64db4cff | 2657 | rdp->blimit = blimit; |
0d8ee37e | 2658 | init_callback_list(rdp); /* Re-enable callbacks on this CPU. */ |
29e37d81 | 2659 | rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; |
c92b131b PM |
2660 | atomic_set(&rdp->dynticks->dynticks, |
2661 | (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1); | |
7cb92499 | 2662 | rcu_prepare_for_idle_init(cpu); |
1304afb2 | 2663 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
2664 | |
2665 | /* | |
2666 | * A new grace period might start here. If so, we won't be part | |
2667 | * of it, but that is OK, as we are currently in a quiescent state. | |
2668 | */ | |
2669 | ||
2670 | /* Exclude any attempts to start a new GP on large systems. */ | |
1304afb2 | 2671 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
64db4cff PM |
2672 | |
2673 | /* Add CPU to rcu_node bitmasks. */ | |
2674 | rnp = rdp->mynode; | |
2675 | mask = rdp->grpmask; | |
2676 | do { | |
2677 | /* Exclude any attempts to start a new GP on small systems. */ | |
1304afb2 | 2678 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
2679 | rnp->qsmaskinit |= mask; |
2680 | mask = rnp->grpmask; | |
d09b62df | 2681 | if (rnp == rdp->mynode) { |
06ae115a PM |
2682 | /* |
2683 | * If there is a grace period in progress, we will | |
2684 | * set up to wait for it next time we run the | |
2685 | * RCU core code. | |
2686 | */ | |
2687 | rdp->gpnum = rnp->completed; | |
d09b62df | 2688 | rdp->completed = rnp->completed; |
06ae115a PM |
2689 | rdp->passed_quiesce = 0; |
2690 | rdp->qs_pending = 0; | |
d4c08f2a | 2691 | trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuonl"); |
d09b62df | 2692 | } |
1304afb2 | 2693 | raw_spin_unlock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
2694 | rnp = rnp->parent; |
2695 | } while (rnp != NULL && !(rnp->qsmaskinit & mask)); | |
2696 | ||
1304afb2 | 2697 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
64db4cff PM |
2698 | } |
2699 | ||
d72bce0e | 2700 | static void __cpuinit rcu_prepare_cpu(int cpu) |
64db4cff | 2701 | { |
6ce75a23 PM |
2702 | struct rcu_state *rsp; |
2703 | ||
2704 | for_each_rcu_flavor(rsp) | |
2705 | rcu_init_percpu_data(cpu, rsp, | |
2706 | strcmp(rsp->name, "rcu_preempt") == 0); | |
64db4cff PM |
2707 | } |
2708 | ||
2709 | /* | |
f41d911f | 2710 | * Handle CPU online/offline notification events. |
64db4cff | 2711 | */ |
9f680ab4 PM |
2712 | static int __cpuinit rcu_cpu_notify(struct notifier_block *self, |
2713 | unsigned long action, void *hcpu) | |
64db4cff PM |
2714 | { |
2715 | long cpu = (long)hcpu; | |
27f4d280 | 2716 | struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu); |
a26ac245 | 2717 | struct rcu_node *rnp = rdp->mynode; |
6ce75a23 | 2718 | struct rcu_state *rsp; |
64db4cff | 2719 | |
300df91c | 2720 | trace_rcu_utilization("Start CPU hotplug"); |
64db4cff PM |
2721 | switch (action) { |
2722 | case CPU_UP_PREPARE: | |
2723 | case CPU_UP_PREPARE_FROZEN: | |
d72bce0e PZ |
2724 | rcu_prepare_cpu(cpu); |
2725 | rcu_prepare_kthreads(cpu); | |
a26ac245 PM |
2726 | break; |
2727 | case CPU_ONLINE: | |
0f962a5e | 2728 | case CPU_DOWN_FAILED: |
5d01bbd1 | 2729 | rcu_boost_kthread_setaffinity(rnp, -1); |
0f962a5e PM |
2730 | break; |
2731 | case CPU_DOWN_PREPARE: | |
5d01bbd1 | 2732 | rcu_boost_kthread_setaffinity(rnp, cpu); |
64db4cff | 2733 | break; |
d0ec774c PM |
2734 | case CPU_DYING: |
2735 | case CPU_DYING_FROZEN: | |
2736 | /* | |
2d999e03 PM |
2737 | * The whole machine is "stopped" except this CPU, so we can |
2738 | * touch any data without introducing corruption. We send the | |
2739 | * dying CPU's callbacks to an arbitrarily chosen online CPU. | |
d0ec774c | 2740 | */ |
6ce75a23 PM |
2741 | for_each_rcu_flavor(rsp) |
2742 | rcu_cleanup_dying_cpu(rsp); | |
7cb92499 | 2743 | rcu_cleanup_after_idle(cpu); |
d0ec774c | 2744 | break; |
64db4cff PM |
2745 | case CPU_DEAD: |
2746 | case CPU_DEAD_FROZEN: | |
2747 | case CPU_UP_CANCELED: | |
2748 | case CPU_UP_CANCELED_FROZEN: | |
6ce75a23 PM |
2749 | for_each_rcu_flavor(rsp) |
2750 | rcu_cleanup_dead_cpu(cpu, rsp); | |
64db4cff PM |
2751 | break; |
2752 | default: | |
2753 | break; | |
2754 | } | |
300df91c | 2755 | trace_rcu_utilization("End CPU hotplug"); |
64db4cff PM |
2756 | return NOTIFY_OK; |
2757 | } | |
2758 | ||
b3dbec76 PM |
2759 | /* |
2760 | * Spawn the kthread that handles this RCU flavor's grace periods. | |
2761 | */ | |
2762 | static int __init rcu_spawn_gp_kthread(void) | |
2763 | { | |
2764 | unsigned long flags; | |
2765 | struct rcu_node *rnp; | |
2766 | struct rcu_state *rsp; | |
2767 | struct task_struct *t; | |
2768 | ||
2769 | for_each_rcu_flavor(rsp) { | |
2770 | t = kthread_run(rcu_gp_kthread, rsp, rsp->name); | |
2771 | BUG_ON(IS_ERR(t)); | |
2772 | rnp = rcu_get_root(rsp); | |
2773 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
2774 | rsp->gp_kthread = t; | |
2775 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
2776 | } | |
2777 | return 0; | |
2778 | } | |
2779 | early_initcall(rcu_spawn_gp_kthread); | |
2780 | ||
bbad9379 PM |
2781 | /* |
2782 | * This function is invoked towards the end of the scheduler's initialization | |
2783 | * process. Before this is called, the idle task might contain | |
2784 | * RCU read-side critical sections (during which time, this idle | |
2785 | * task is booting the system). After this function is called, the | |
2786 | * idle tasks are prohibited from containing RCU read-side critical | |
2787 | * sections. This function also enables RCU lockdep checking. | |
2788 | */ | |
2789 | void rcu_scheduler_starting(void) | |
2790 | { | |
2791 | WARN_ON(num_online_cpus() != 1); | |
2792 | WARN_ON(nr_context_switches() > 0); | |
2793 | rcu_scheduler_active = 1; | |
2794 | } | |
2795 | ||
64db4cff PM |
2796 | /* |
2797 | * Compute the per-level fanout, either using the exact fanout specified | |
2798 | * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. | |
2799 | */ | |
2800 | #ifdef CONFIG_RCU_FANOUT_EXACT | |
2801 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
2802 | { | |
2803 | int i; | |
2804 | ||
f885b7f2 | 2805 | for (i = rcu_num_lvls - 1; i > 0; i--) |
64db4cff | 2806 | rsp->levelspread[i] = CONFIG_RCU_FANOUT; |
f885b7f2 | 2807 | rsp->levelspread[0] = rcu_fanout_leaf; |
64db4cff PM |
2808 | } |
2809 | #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
2810 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
2811 | { | |
2812 | int ccur; | |
2813 | int cprv; | |
2814 | int i; | |
2815 | ||
4dbd6bb3 | 2816 | cprv = nr_cpu_ids; |
f885b7f2 | 2817 | for (i = rcu_num_lvls - 1; i >= 0; i--) { |
64db4cff PM |
2818 | ccur = rsp->levelcnt[i]; |
2819 | rsp->levelspread[i] = (cprv + ccur - 1) / ccur; | |
2820 | cprv = ccur; | |
2821 | } | |
2822 | } | |
2823 | #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
2824 | ||
2825 | /* | |
2826 | * Helper function for rcu_init() that initializes one rcu_state structure. | |
2827 | */ | |
394f99a9 LJ |
2828 | static void __init rcu_init_one(struct rcu_state *rsp, |
2829 | struct rcu_data __percpu *rda) | |
64db4cff | 2830 | { |
394f2769 PM |
2831 | static char *buf[] = { "rcu_node_0", |
2832 | "rcu_node_1", | |
2833 | "rcu_node_2", | |
2834 | "rcu_node_3" }; /* Match MAX_RCU_LVLS */ | |
2835 | static char *fqs[] = { "rcu_node_fqs_0", | |
2836 | "rcu_node_fqs_1", | |
2837 | "rcu_node_fqs_2", | |
2838 | "rcu_node_fqs_3" }; /* Match MAX_RCU_LVLS */ | |
64db4cff PM |
2839 | int cpustride = 1; |
2840 | int i; | |
2841 | int j; | |
2842 | struct rcu_node *rnp; | |
2843 | ||
b6407e86 PM |
2844 | BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ |
2845 | ||
64db4cff PM |
2846 | /* Initialize the level-tracking arrays. */ |
2847 | ||
f885b7f2 PM |
2848 | for (i = 0; i < rcu_num_lvls; i++) |
2849 | rsp->levelcnt[i] = num_rcu_lvl[i]; | |
2850 | for (i = 1; i < rcu_num_lvls; i++) | |
64db4cff PM |
2851 | rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; |
2852 | rcu_init_levelspread(rsp); | |
2853 | ||
2854 | /* Initialize the elements themselves, starting from the leaves. */ | |
2855 | ||
f885b7f2 | 2856 | for (i = rcu_num_lvls - 1; i >= 0; i--) { |
64db4cff PM |
2857 | cpustride *= rsp->levelspread[i]; |
2858 | rnp = rsp->level[i]; | |
2859 | for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { | |
1304afb2 | 2860 | raw_spin_lock_init(&rnp->lock); |
b6407e86 PM |
2861 | lockdep_set_class_and_name(&rnp->lock, |
2862 | &rcu_node_class[i], buf[i]); | |
394f2769 PM |
2863 | raw_spin_lock_init(&rnp->fqslock); |
2864 | lockdep_set_class_and_name(&rnp->fqslock, | |
2865 | &rcu_fqs_class[i], fqs[i]); | |
25d30cf4 PM |
2866 | rnp->gpnum = rsp->gpnum; |
2867 | rnp->completed = rsp->completed; | |
64db4cff PM |
2868 | rnp->qsmask = 0; |
2869 | rnp->qsmaskinit = 0; | |
2870 | rnp->grplo = j * cpustride; | |
2871 | rnp->grphi = (j + 1) * cpustride - 1; | |
2872 | if (rnp->grphi >= NR_CPUS) | |
2873 | rnp->grphi = NR_CPUS - 1; | |
2874 | if (i == 0) { | |
2875 | rnp->grpnum = 0; | |
2876 | rnp->grpmask = 0; | |
2877 | rnp->parent = NULL; | |
2878 | } else { | |
2879 | rnp->grpnum = j % rsp->levelspread[i - 1]; | |
2880 | rnp->grpmask = 1UL << rnp->grpnum; | |
2881 | rnp->parent = rsp->level[i - 1] + | |
2882 | j / rsp->levelspread[i - 1]; | |
2883 | } | |
2884 | rnp->level = i; | |
12f5f524 | 2885 | INIT_LIST_HEAD(&rnp->blkd_tasks); |
64db4cff PM |
2886 | } |
2887 | } | |
0c34029a | 2888 | |
394f99a9 | 2889 | rsp->rda = rda; |
b3dbec76 | 2890 | init_waitqueue_head(&rsp->gp_wq); |
f885b7f2 | 2891 | rnp = rsp->level[rcu_num_lvls - 1]; |
0c34029a | 2892 | for_each_possible_cpu(i) { |
4a90a068 | 2893 | while (i > rnp->grphi) |
0c34029a | 2894 | rnp++; |
394f99a9 | 2895 | per_cpu_ptr(rsp->rda, i)->mynode = rnp; |
0c34029a LJ |
2896 | rcu_boot_init_percpu_data(i, rsp); |
2897 | } | |
6ce75a23 | 2898 | list_add(&rsp->flavors, &rcu_struct_flavors); |
64db4cff PM |
2899 | } |
2900 | ||
f885b7f2 PM |
2901 | /* |
2902 | * Compute the rcu_node tree geometry from kernel parameters. This cannot | |
2903 | * replace the definitions in rcutree.h because those are needed to size | |
2904 | * the ->node array in the rcu_state structure. | |
2905 | */ | |
2906 | static void __init rcu_init_geometry(void) | |
2907 | { | |
2908 | int i; | |
2909 | int j; | |
cca6f393 | 2910 | int n = nr_cpu_ids; |
f885b7f2 PM |
2911 | int rcu_capacity[MAX_RCU_LVLS + 1]; |
2912 | ||
2913 | /* If the compile-time values are accurate, just leave. */ | |
b17c7035 PM |
2914 | if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF && |
2915 | nr_cpu_ids == NR_CPUS) | |
f885b7f2 PM |
2916 | return; |
2917 | ||
2918 | /* | |
2919 | * Compute number of nodes that can be handled an rcu_node tree | |
2920 | * with the given number of levels. Setting rcu_capacity[0] makes | |
2921 | * some of the arithmetic easier. | |
2922 | */ | |
2923 | rcu_capacity[0] = 1; | |
2924 | rcu_capacity[1] = rcu_fanout_leaf; | |
2925 | for (i = 2; i <= MAX_RCU_LVLS; i++) | |
2926 | rcu_capacity[i] = rcu_capacity[i - 1] * CONFIG_RCU_FANOUT; | |
2927 | ||
2928 | /* | |
2929 | * The boot-time rcu_fanout_leaf parameter is only permitted | |
2930 | * to increase the leaf-level fanout, not decrease it. Of course, | |
2931 | * the leaf-level fanout cannot exceed the number of bits in | |
2932 | * the rcu_node masks. Finally, the tree must be able to accommodate | |
2933 | * the configured number of CPUs. Complain and fall back to the | |
2934 | * compile-time values if these limits are exceeded. | |
2935 | */ | |
2936 | if (rcu_fanout_leaf < CONFIG_RCU_FANOUT_LEAF || | |
2937 | rcu_fanout_leaf > sizeof(unsigned long) * 8 || | |
2938 | n > rcu_capacity[MAX_RCU_LVLS]) { | |
2939 | WARN_ON(1); | |
2940 | return; | |
2941 | } | |
2942 | ||
2943 | /* Calculate the number of rcu_nodes at each level of the tree. */ | |
2944 | for (i = 1; i <= MAX_RCU_LVLS; i++) | |
2945 | if (n <= rcu_capacity[i]) { | |
2946 | for (j = 0; j <= i; j++) | |
2947 | num_rcu_lvl[j] = | |
2948 | DIV_ROUND_UP(n, rcu_capacity[i - j]); | |
2949 | rcu_num_lvls = i; | |
2950 | for (j = i + 1; j <= MAX_RCU_LVLS; j++) | |
2951 | num_rcu_lvl[j] = 0; | |
2952 | break; | |
2953 | } | |
2954 | ||
2955 | /* Calculate the total number of rcu_node structures. */ | |
2956 | rcu_num_nodes = 0; | |
2957 | for (i = 0; i <= MAX_RCU_LVLS; i++) | |
2958 | rcu_num_nodes += num_rcu_lvl[i]; | |
2959 | rcu_num_nodes -= n; | |
2960 | } | |
2961 | ||
9f680ab4 | 2962 | void __init rcu_init(void) |
64db4cff | 2963 | { |
017c4261 | 2964 | int cpu; |
9f680ab4 | 2965 | |
f41d911f | 2966 | rcu_bootup_announce(); |
f885b7f2 | 2967 | rcu_init_geometry(); |
394f99a9 LJ |
2968 | rcu_init_one(&rcu_sched_state, &rcu_sched_data); |
2969 | rcu_init_one(&rcu_bh_state, &rcu_bh_data); | |
f41d911f | 2970 | __rcu_init_preempt(); |
09223371 | 2971 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
9f680ab4 PM |
2972 | |
2973 | /* | |
2974 | * We don't need protection against CPU-hotplug here because | |
2975 | * this is called early in boot, before either interrupts | |
2976 | * or the scheduler are operational. | |
2977 | */ | |
2978 | cpu_notifier(rcu_cpu_notify, 0); | |
017c4261 PM |
2979 | for_each_online_cpu(cpu) |
2980 | rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); | |
c68de209 | 2981 | check_cpu_stall_init(); |
64db4cff PM |
2982 | } |
2983 | ||
1eba8f84 | 2984 | #include "rcutree_plugin.h" |