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