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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> | |
64db4cff | 55 | |
9f77da9f | 56 | #include "rcutree.h" |
29c00b4a PM |
57 | #include <trace/events/rcu.h> |
58 | ||
59 | #include "rcu.h" | |
9f77da9f | 60 | |
64db4cff PM |
61 | /* Data structures. */ |
62 | ||
f885b7f2 | 63 | static struct lock_class_key rcu_node_class[RCU_NUM_LVLS]; |
88b91c7c | 64 | |
037b64ed | 65 | #define RCU_STATE_INITIALIZER(sname, cr) { \ |
6c90cc7b | 66 | .level = { &sname##_state.node[0] }, \ |
037b64ed | 67 | .call = cr, \ |
af446b70 | 68 | .fqs_state = RCU_GP_IDLE, \ |
64db4cff PM |
69 | .gpnum = -300, \ |
70 | .completed = -300, \ | |
6c90cc7b PM |
71 | .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.onofflock), \ |
72 | .orphan_nxttail = &sname##_state.orphan_nxtlist, \ | |
73 | .orphan_donetail = &sname##_state.orphan_donelist, \ | |
7be7f0be | 74 | .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \ |
6c90cc7b | 75 | .name = #sname, \ |
64db4cff PM |
76 | } |
77 | ||
037b64ed PM |
78 | struct rcu_state rcu_sched_state = |
79 | RCU_STATE_INITIALIZER(rcu_sched, call_rcu_sched); | |
d6714c22 | 80 | DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); |
64db4cff | 81 | |
037b64ed | 82 | struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh, call_rcu_bh); |
6258c4fb | 83 | DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); |
b1f77b05 | 84 | |
27f4d280 | 85 | static struct rcu_state *rcu_state; |
6ce75a23 | 86 | LIST_HEAD(rcu_struct_flavors); |
27f4d280 | 87 | |
f885b7f2 PM |
88 | /* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */ |
89 | static int rcu_fanout_leaf = CONFIG_RCU_FANOUT_LEAF; | |
90 | module_param(rcu_fanout_leaf, int, 0); | |
91 | int rcu_num_lvls __read_mostly = RCU_NUM_LVLS; | |
92 | static int num_rcu_lvl[] = { /* Number of rcu_nodes at specified level. */ | |
93 | NUM_RCU_LVL_0, | |
94 | NUM_RCU_LVL_1, | |
95 | NUM_RCU_LVL_2, | |
96 | NUM_RCU_LVL_3, | |
97 | NUM_RCU_LVL_4, | |
98 | }; | |
99 | int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ | |
100 | ||
b0d30417 PM |
101 | /* |
102 | * The rcu_scheduler_active variable transitions from zero to one just | |
103 | * before the first task is spawned. So when this variable is zero, RCU | |
104 | * can assume that there is but one task, allowing RCU to (for example) | |
105 | * optimized synchronize_sched() to a simple barrier(). When this variable | |
106 | * is one, RCU must actually do all the hard work required to detect real | |
107 | * grace periods. This variable is also used to suppress boot-time false | |
108 | * positives from lockdep-RCU error checking. | |
109 | */ | |
bbad9379 PM |
110 | int rcu_scheduler_active __read_mostly; |
111 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); | |
112 | ||
b0d30417 PM |
113 | /* |
114 | * The rcu_scheduler_fully_active variable transitions from zero to one | |
115 | * during the early_initcall() processing, which is after the scheduler | |
116 | * is capable of creating new tasks. So RCU processing (for example, | |
117 | * creating tasks for RCU priority boosting) must be delayed until after | |
118 | * rcu_scheduler_fully_active transitions from zero to one. We also | |
119 | * currently delay invocation of any RCU callbacks until after this point. | |
120 | * | |
121 | * It might later prove better for people registering RCU callbacks during | |
122 | * early boot to take responsibility for these callbacks, but one step at | |
123 | * a time. | |
124 | */ | |
125 | static int rcu_scheduler_fully_active __read_mostly; | |
126 | ||
a46e0899 PM |
127 | #ifdef CONFIG_RCU_BOOST |
128 | ||
a26ac245 PM |
129 | /* |
130 | * Control variables for per-CPU and per-rcu_node kthreads. These | |
131 | * handle all flavors of RCU. | |
132 | */ | |
133 | static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); | |
d71df90e | 134 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); |
15ba0ba8 | 135 | DEFINE_PER_CPU(int, rcu_cpu_kthread_cpu); |
5ece5bab | 136 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); |
d71df90e | 137 | DEFINE_PER_CPU(char, rcu_cpu_has_work); |
a26ac245 | 138 | |
a46e0899 PM |
139 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
140 | ||
0f962a5e | 141 | static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); |
a46e0899 PM |
142 | static void invoke_rcu_core(void); |
143 | static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp); | |
a26ac245 | 144 | |
4a298656 PM |
145 | /* |
146 | * Track the rcutorture test sequence number and the update version | |
147 | * number within a given test. The rcutorture_testseq is incremented | |
148 | * on every rcutorture module load and unload, so has an odd value | |
149 | * when a test is running. The rcutorture_vernum is set to zero | |
150 | * when rcutorture starts and is incremented on each rcutorture update. | |
151 | * These variables enable correlating rcutorture output with the | |
152 | * RCU tracing information. | |
153 | */ | |
154 | unsigned long rcutorture_testseq; | |
155 | unsigned long rcutorture_vernum; | |
156 | ||
fc2219d4 PM |
157 | /* |
158 | * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s | |
159 | * permit this function to be invoked without holding the root rcu_node | |
160 | * structure's ->lock, but of course results can be subject to change. | |
161 | */ | |
162 | static int rcu_gp_in_progress(struct rcu_state *rsp) | |
163 | { | |
164 | return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); | |
165 | } | |
166 | ||
b1f77b05 | 167 | /* |
d6714c22 | 168 | * Note a quiescent state. Because we do not need to know |
b1f77b05 | 169 | * how many quiescent states passed, just if there was at least |
d6714c22 | 170 | * one since the start of the grace period, this just sets a flag. |
e4cc1f22 | 171 | * The caller must have disabled preemption. |
b1f77b05 | 172 | */ |
d6714c22 | 173 | void rcu_sched_qs(int cpu) |
b1f77b05 | 174 | { |
25502a6c | 175 | struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); |
f41d911f | 176 | |
e4cc1f22 | 177 | rdp->passed_quiesce_gpnum = rdp->gpnum; |
c3422bea | 178 | barrier(); |
e4cc1f22 | 179 | if (rdp->passed_quiesce == 0) |
d4c08f2a | 180 | trace_rcu_grace_period("rcu_sched", rdp->gpnum, "cpuqs"); |
e4cc1f22 | 181 | rdp->passed_quiesce = 1; |
b1f77b05 IM |
182 | } |
183 | ||
d6714c22 | 184 | void rcu_bh_qs(int cpu) |
b1f77b05 | 185 | { |
25502a6c | 186 | struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); |
f41d911f | 187 | |
e4cc1f22 | 188 | rdp->passed_quiesce_gpnum = rdp->gpnum; |
c3422bea | 189 | barrier(); |
e4cc1f22 | 190 | if (rdp->passed_quiesce == 0) |
d4c08f2a | 191 | trace_rcu_grace_period("rcu_bh", rdp->gpnum, "cpuqs"); |
e4cc1f22 | 192 | rdp->passed_quiesce = 1; |
b1f77b05 | 193 | } |
64db4cff | 194 | |
25502a6c PM |
195 | /* |
196 | * Note a context switch. This is a quiescent state for RCU-sched, | |
197 | * and requires special handling for preemptible RCU. | |
e4cc1f22 | 198 | * The caller must have disabled preemption. |
25502a6c PM |
199 | */ |
200 | void rcu_note_context_switch(int cpu) | |
201 | { | |
300df91c | 202 | trace_rcu_utilization("Start context switch"); |
25502a6c | 203 | rcu_sched_qs(cpu); |
cba6d0d6 | 204 | rcu_preempt_note_context_switch(cpu); |
300df91c | 205 | trace_rcu_utilization("End context switch"); |
25502a6c | 206 | } |
29ce8310 | 207 | EXPORT_SYMBOL_GPL(rcu_note_context_switch); |
25502a6c | 208 | |
90a4d2c0 | 209 | DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
29e37d81 | 210 | .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE, |
23b5c8fa | 211 | .dynticks = ATOMIC_INIT(1), |
90a4d2c0 | 212 | }; |
64db4cff | 213 | |
e0f23060 | 214 | static int blimit = 10; /* Maximum callbacks per rcu_do_batch. */ |
64db4cff PM |
215 | static int qhimark = 10000; /* If this many pending, ignore blimit. */ |
216 | static int qlowmark = 100; /* Once only this many pending, use blimit. */ | |
217 | ||
3d76c082 PM |
218 | module_param(blimit, int, 0); |
219 | module_param(qhimark, int, 0); | |
220 | module_param(qlowmark, int, 0); | |
221 | ||
13cfcca0 PM |
222 | int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */ |
223 | int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT; | |
224 | ||
f2e0dd70 | 225 | module_param(rcu_cpu_stall_suppress, int, 0644); |
13cfcca0 | 226 | module_param(rcu_cpu_stall_timeout, int, 0644); |
742734ee | 227 | |
4cdfc175 PM |
228 | static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)); |
229 | static void force_quiescent_state(struct rcu_state *rsp); | |
a157229c | 230 | static int rcu_pending(int cpu); |
64db4cff PM |
231 | |
232 | /* | |
d6714c22 | 233 | * Return the number of RCU-sched batches processed thus far for debug & stats. |
64db4cff | 234 | */ |
d6714c22 | 235 | long rcu_batches_completed_sched(void) |
64db4cff | 236 | { |
d6714c22 | 237 | return rcu_sched_state.completed; |
64db4cff | 238 | } |
d6714c22 | 239 | EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
64db4cff PM |
240 | |
241 | /* | |
242 | * Return the number of RCU BH batches processed thus far for debug & stats. | |
243 | */ | |
244 | long rcu_batches_completed_bh(void) | |
245 | { | |
246 | return rcu_bh_state.completed; | |
247 | } | |
248 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); | |
249 | ||
bf66f18e PM |
250 | /* |
251 | * Force a quiescent state for RCU BH. | |
252 | */ | |
253 | void rcu_bh_force_quiescent_state(void) | |
254 | { | |
4cdfc175 | 255 | force_quiescent_state(&rcu_bh_state); |
bf66f18e PM |
256 | } |
257 | EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); | |
258 | ||
4a298656 PM |
259 | /* |
260 | * Record the number of times rcutorture tests have been initiated and | |
261 | * terminated. This information allows the debugfs tracing stats to be | |
262 | * correlated to the rcutorture messages, even when the rcutorture module | |
263 | * is being repeatedly loaded and unloaded. In other words, we cannot | |
264 | * store this state in rcutorture itself. | |
265 | */ | |
266 | void rcutorture_record_test_transition(void) | |
267 | { | |
268 | rcutorture_testseq++; | |
269 | rcutorture_vernum = 0; | |
270 | } | |
271 | EXPORT_SYMBOL_GPL(rcutorture_record_test_transition); | |
272 | ||
273 | /* | |
274 | * Record the number of writer passes through the current rcutorture test. | |
275 | * This is also used to correlate debugfs tracing stats with the rcutorture | |
276 | * messages. | |
277 | */ | |
278 | void rcutorture_record_progress(unsigned long vernum) | |
279 | { | |
280 | rcutorture_vernum++; | |
281 | } | |
282 | EXPORT_SYMBOL_GPL(rcutorture_record_progress); | |
283 | ||
bf66f18e PM |
284 | /* |
285 | * Force a quiescent state for RCU-sched. | |
286 | */ | |
287 | void rcu_sched_force_quiescent_state(void) | |
288 | { | |
4cdfc175 | 289 | force_quiescent_state(&rcu_sched_state); |
bf66f18e PM |
290 | } |
291 | EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); | |
292 | ||
64db4cff PM |
293 | /* |
294 | * Does the CPU have callbacks ready to be invoked? | |
295 | */ | |
296 | static int | |
297 | cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) | |
298 | { | |
299 | return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]; | |
300 | } | |
301 | ||
302 | /* | |
303 | * Does the current CPU require a yet-as-unscheduled grace period? | |
304 | */ | |
305 | static int | |
306 | cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) | |
307 | { | |
a10d206e PM |
308 | return *rdp->nxttail[RCU_DONE_TAIL + |
309 | ACCESS_ONCE(rsp->completed) != rdp->completed] && | |
310 | !rcu_gp_in_progress(rsp); | |
64db4cff PM |
311 | } |
312 | ||
313 | /* | |
314 | * Return the root node of the specified rcu_state structure. | |
315 | */ | |
316 | static struct rcu_node *rcu_get_root(struct rcu_state *rsp) | |
317 | { | |
318 | return &rsp->node[0]; | |
319 | } | |
320 | ||
64db4cff PM |
321 | /* |
322 | * If the specified CPU is offline, tell the caller that it is in | |
323 | * a quiescent state. Otherwise, whack it with a reschedule IPI. | |
324 | * Grace periods can end up waiting on an offline CPU when that | |
325 | * CPU is in the process of coming online -- it will be added to the | |
326 | * rcu_node bitmasks before it actually makes it online. The same thing | |
327 | * can happen while a CPU is in the process of coming online. Because this | |
328 | * race is quite rare, we check for it after detecting that the grace | |
329 | * period has been delayed rather than checking each and every CPU | |
330 | * each and every time we start a new grace period. | |
331 | */ | |
332 | static int rcu_implicit_offline_qs(struct rcu_data *rdp) | |
333 | { | |
334 | /* | |
2036d94a PM |
335 | * If the CPU is offline for more than a jiffy, it is in a quiescent |
336 | * state. We can trust its state not to change because interrupts | |
337 | * are disabled. The reason for the jiffy's worth of slack is to | |
338 | * handle CPUs initializing on the way up and finding their way | |
339 | * to the idle loop on the way down. | |
64db4cff | 340 | */ |
2036d94a PM |
341 | if (cpu_is_offline(rdp->cpu) && |
342 | ULONG_CMP_LT(rdp->rsp->gp_start + 2, jiffies)) { | |
d4c08f2a | 343 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "ofl"); |
64db4cff PM |
344 | rdp->offline_fqs++; |
345 | return 1; | |
346 | } | |
64db4cff PM |
347 | return 0; |
348 | } | |
349 | ||
9b2e4f18 PM |
350 | /* |
351 | * rcu_idle_enter_common - inform RCU that current CPU is moving towards idle | |
352 | * | |
353 | * If the new value of the ->dynticks_nesting counter now is zero, | |
354 | * we really have entered idle, and must do the appropriate accounting. | |
355 | * The caller must have disabled interrupts. | |
356 | */ | |
4145fa7f | 357 | static void rcu_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval) |
9b2e4f18 | 358 | { |
facc4e15 | 359 | trace_rcu_dyntick("Start", oldval, 0); |
99745b6a | 360 | if (!is_idle_task(current)) { |
0989cb46 PM |
361 | struct task_struct *idle = idle_task(smp_processor_id()); |
362 | ||
facc4e15 | 363 | trace_rcu_dyntick("Error on entry: not idle task", oldval, 0); |
bf1304e9 | 364 | ftrace_dump(DUMP_ORIG); |
0989cb46 PM |
365 | WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
366 | current->pid, current->comm, | |
367 | idle->pid, idle->comm); /* must be idle task! */ | |
9b2e4f18 | 368 | } |
aea1b35e | 369 | rcu_prepare_for_idle(smp_processor_id()); |
9b2e4f18 PM |
370 | /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
371 | smp_mb__before_atomic_inc(); /* See above. */ | |
372 | atomic_inc(&rdtp->dynticks); | |
373 | smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */ | |
374 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); | |
c44e2cdd PM |
375 | |
376 | /* | |
377 | * The idle task is not permitted to enter the idle loop while | |
378 | * in an RCU read-side critical section. | |
379 | */ | |
380 | rcu_lockdep_assert(!lock_is_held(&rcu_lock_map), | |
381 | "Illegal idle entry in RCU read-side critical section."); | |
382 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), | |
383 | "Illegal idle entry in RCU-bh read-side critical section."); | |
384 | rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), | |
385 | "Illegal idle entry in RCU-sched read-side critical section."); | |
9b2e4f18 | 386 | } |
64db4cff PM |
387 | |
388 | /** | |
9b2e4f18 | 389 | * rcu_idle_enter - inform RCU that current CPU is entering idle |
64db4cff | 390 | * |
9b2e4f18 | 391 | * Enter idle mode, in other words, -leave- the mode in which RCU |
64db4cff | 392 | * read-side critical sections can occur. (Though RCU read-side |
9b2e4f18 PM |
393 | * critical sections can occur in irq handlers in idle, a possibility |
394 | * handled by irq_enter() and irq_exit().) | |
395 | * | |
396 | * We crowbar the ->dynticks_nesting field to zero to allow for | |
397 | * the possibility of usermode upcalls having messed up our count | |
398 | * of interrupt nesting level during the prior busy period. | |
64db4cff | 399 | */ |
9b2e4f18 | 400 | void rcu_idle_enter(void) |
64db4cff PM |
401 | { |
402 | unsigned long flags; | |
4145fa7f | 403 | long long oldval; |
64db4cff PM |
404 | struct rcu_dynticks *rdtp; |
405 | ||
64db4cff PM |
406 | local_irq_save(flags); |
407 | rdtp = &__get_cpu_var(rcu_dynticks); | |
4145fa7f | 408 | oldval = rdtp->dynticks_nesting; |
29e37d81 PM |
409 | WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0); |
410 | if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) | |
411 | rdtp->dynticks_nesting = 0; | |
412 | else | |
413 | rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE; | |
4145fa7f | 414 | rcu_idle_enter_common(rdtp, oldval); |
64db4cff PM |
415 | local_irq_restore(flags); |
416 | } | |
8a2ecf47 | 417 | EXPORT_SYMBOL_GPL(rcu_idle_enter); |
64db4cff | 418 | |
9b2e4f18 PM |
419 | /** |
420 | * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle | |
421 | * | |
422 | * Exit from an interrupt handler, which might possibly result in entering | |
423 | * idle mode, in other words, leaving the mode in which read-side critical | |
424 | * sections can occur. | |
64db4cff | 425 | * |
9b2e4f18 PM |
426 | * This code assumes that the idle loop never does anything that might |
427 | * result in unbalanced calls to irq_enter() and irq_exit(). If your | |
428 | * architecture violates this assumption, RCU will give you what you | |
429 | * deserve, good and hard. But very infrequently and irreproducibly. | |
430 | * | |
431 | * Use things like work queues to work around this limitation. | |
432 | * | |
433 | * You have been warned. | |
64db4cff | 434 | */ |
9b2e4f18 | 435 | void rcu_irq_exit(void) |
64db4cff PM |
436 | { |
437 | unsigned long flags; | |
4145fa7f | 438 | long long oldval; |
64db4cff PM |
439 | struct rcu_dynticks *rdtp; |
440 | ||
441 | local_irq_save(flags); | |
442 | rdtp = &__get_cpu_var(rcu_dynticks); | |
4145fa7f | 443 | oldval = rdtp->dynticks_nesting; |
9b2e4f18 PM |
444 | rdtp->dynticks_nesting--; |
445 | WARN_ON_ONCE(rdtp->dynticks_nesting < 0); | |
b6fc6020 FW |
446 | if (rdtp->dynticks_nesting) |
447 | trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting); | |
448 | else | |
449 | rcu_idle_enter_common(rdtp, oldval); | |
9b2e4f18 PM |
450 | local_irq_restore(flags); |
451 | } | |
452 | ||
453 | /* | |
454 | * rcu_idle_exit_common - inform RCU that current CPU is moving away from idle | |
455 | * | |
456 | * If the new value of the ->dynticks_nesting counter was previously zero, | |
457 | * we really have exited idle, and must do the appropriate accounting. | |
458 | * The caller must have disabled interrupts. | |
459 | */ | |
460 | static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval) | |
461 | { | |
23b5c8fa PM |
462 | smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */ |
463 | atomic_inc(&rdtp->dynticks); | |
464 | /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ | |
465 | smp_mb__after_atomic_inc(); /* See above. */ | |
466 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); | |
7cb92499 | 467 | rcu_cleanup_after_idle(smp_processor_id()); |
4145fa7f | 468 | trace_rcu_dyntick("End", oldval, rdtp->dynticks_nesting); |
99745b6a | 469 | if (!is_idle_task(current)) { |
0989cb46 PM |
470 | struct task_struct *idle = idle_task(smp_processor_id()); |
471 | ||
4145fa7f PM |
472 | trace_rcu_dyntick("Error on exit: not idle task", |
473 | oldval, rdtp->dynticks_nesting); | |
bf1304e9 | 474 | ftrace_dump(DUMP_ORIG); |
0989cb46 PM |
475 | WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
476 | current->pid, current->comm, | |
477 | idle->pid, idle->comm); /* must be idle task! */ | |
9b2e4f18 PM |
478 | } |
479 | } | |
480 | ||
481 | /** | |
482 | * rcu_idle_exit - inform RCU that current CPU is leaving idle | |
483 | * | |
484 | * Exit idle mode, in other words, -enter- the mode in which RCU | |
485 | * read-side critical sections can occur. | |
486 | * | |
29e37d81 | 487 | * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to |
4145fa7f | 488 | * allow for the possibility of usermode upcalls messing up our count |
9b2e4f18 PM |
489 | * of interrupt nesting level during the busy period that is just |
490 | * now starting. | |
491 | */ | |
492 | void rcu_idle_exit(void) | |
493 | { | |
494 | unsigned long flags; | |
495 | struct rcu_dynticks *rdtp; | |
496 | long long oldval; | |
497 | ||
498 | local_irq_save(flags); | |
499 | rdtp = &__get_cpu_var(rcu_dynticks); | |
500 | oldval = rdtp->dynticks_nesting; | |
29e37d81 PM |
501 | WARN_ON_ONCE(oldval < 0); |
502 | if (oldval & DYNTICK_TASK_NEST_MASK) | |
503 | rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE; | |
504 | else | |
505 | rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; | |
9b2e4f18 PM |
506 | rcu_idle_exit_common(rdtp, oldval); |
507 | local_irq_restore(flags); | |
508 | } | |
8a2ecf47 | 509 | EXPORT_SYMBOL_GPL(rcu_idle_exit); |
9b2e4f18 PM |
510 | |
511 | /** | |
512 | * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle | |
513 | * | |
514 | * Enter an interrupt handler, which might possibly result in exiting | |
515 | * idle mode, in other words, entering the mode in which read-side critical | |
516 | * sections can occur. | |
517 | * | |
518 | * Note that the Linux kernel is fully capable of entering an interrupt | |
519 | * handler that it never exits, for example when doing upcalls to | |
520 | * user mode! This code assumes that the idle loop never does upcalls to | |
521 | * user mode. If your architecture does do upcalls from the idle loop (or | |
522 | * does anything else that results in unbalanced calls to the irq_enter() | |
523 | * and irq_exit() functions), RCU will give you what you deserve, good | |
524 | * and hard. But very infrequently and irreproducibly. | |
525 | * | |
526 | * Use things like work queues to work around this limitation. | |
527 | * | |
528 | * You have been warned. | |
529 | */ | |
530 | void rcu_irq_enter(void) | |
531 | { | |
532 | unsigned long flags; | |
533 | struct rcu_dynticks *rdtp; | |
534 | long long oldval; | |
535 | ||
536 | local_irq_save(flags); | |
537 | rdtp = &__get_cpu_var(rcu_dynticks); | |
538 | oldval = rdtp->dynticks_nesting; | |
539 | rdtp->dynticks_nesting++; | |
540 | WARN_ON_ONCE(rdtp->dynticks_nesting == 0); | |
b6fc6020 FW |
541 | if (oldval) |
542 | trace_rcu_dyntick("++=", oldval, rdtp->dynticks_nesting); | |
543 | else | |
544 | rcu_idle_exit_common(rdtp, oldval); | |
64db4cff | 545 | local_irq_restore(flags); |
64db4cff PM |
546 | } |
547 | ||
548 | /** | |
549 | * rcu_nmi_enter - inform RCU of entry to NMI context | |
550 | * | |
551 | * If the CPU was idle with dynamic ticks active, and there is no | |
552 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
553 | * RCU grace-period handling know that the CPU is active. | |
554 | */ | |
555 | void rcu_nmi_enter(void) | |
556 | { | |
557 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
558 | ||
23b5c8fa PM |
559 | if (rdtp->dynticks_nmi_nesting == 0 && |
560 | (atomic_read(&rdtp->dynticks) & 0x1)) | |
64db4cff | 561 | return; |
23b5c8fa PM |
562 | rdtp->dynticks_nmi_nesting++; |
563 | smp_mb__before_atomic_inc(); /* Force delay from prior write. */ | |
564 | atomic_inc(&rdtp->dynticks); | |
565 | /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ | |
566 | smp_mb__after_atomic_inc(); /* See above. */ | |
567 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); | |
64db4cff PM |
568 | } |
569 | ||
570 | /** | |
571 | * rcu_nmi_exit - inform RCU of exit from NMI context | |
572 | * | |
573 | * If the CPU was idle with dynamic ticks active, and there is no | |
574 | * irq handler running, this updates rdtp->dynticks_nmi to let the | |
575 | * RCU grace-period handling know that the CPU is no longer active. | |
576 | */ | |
577 | void rcu_nmi_exit(void) | |
578 | { | |
579 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); | |
580 | ||
23b5c8fa PM |
581 | if (rdtp->dynticks_nmi_nesting == 0 || |
582 | --rdtp->dynticks_nmi_nesting != 0) | |
64db4cff | 583 | return; |
23b5c8fa PM |
584 | /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
585 | smp_mb__before_atomic_inc(); /* See above. */ | |
586 | atomic_inc(&rdtp->dynticks); | |
587 | smp_mb__after_atomic_inc(); /* Force delay to next write. */ | |
588 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); | |
64db4cff PM |
589 | } |
590 | ||
591 | /** | |
9b2e4f18 | 592 | * rcu_is_cpu_idle - see if RCU thinks that the current CPU is idle |
64db4cff | 593 | * |
9b2e4f18 | 594 | * If the current CPU is in its idle loop and is neither in an interrupt |
34240697 | 595 | * or NMI handler, return true. |
64db4cff | 596 | */ |
9b2e4f18 | 597 | int rcu_is_cpu_idle(void) |
64db4cff | 598 | { |
34240697 PM |
599 | int ret; |
600 | ||
601 | preempt_disable(); | |
602 | ret = (atomic_read(&__get_cpu_var(rcu_dynticks).dynticks) & 0x1) == 0; | |
603 | preempt_enable(); | |
604 | return ret; | |
64db4cff | 605 | } |
e6b80a3b | 606 | EXPORT_SYMBOL(rcu_is_cpu_idle); |
64db4cff | 607 | |
62fde6ed | 608 | #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) |
c0d6d01b PM |
609 | |
610 | /* | |
611 | * Is the current CPU online? Disable preemption to avoid false positives | |
612 | * that could otherwise happen due to the current CPU number being sampled, | |
613 | * this task being preempted, its old CPU being taken offline, resuming | |
614 | * on some other CPU, then determining that its old CPU is now offline. | |
615 | * It is OK to use RCU on an offline processor during initial boot, hence | |
2036d94a PM |
616 | * the check for rcu_scheduler_fully_active. Note also that it is OK |
617 | * for a CPU coming online to use RCU for one jiffy prior to marking itself | |
618 | * online in the cpu_online_mask. Similarly, it is OK for a CPU going | |
619 | * offline to continue to use RCU for one jiffy after marking itself | |
620 | * offline in the cpu_online_mask. This leniency is necessary given the | |
621 | * non-atomic nature of the online and offline processing, for example, | |
622 | * the fact that a CPU enters the scheduler after completing the CPU_DYING | |
623 | * notifiers. | |
624 | * | |
625 | * This is also why RCU internally marks CPUs online during the | |
626 | * CPU_UP_PREPARE phase and offline during the CPU_DEAD phase. | |
c0d6d01b PM |
627 | * |
628 | * Disable checking if in an NMI handler because we cannot safely report | |
629 | * errors from NMI handlers anyway. | |
630 | */ | |
631 | bool rcu_lockdep_current_cpu_online(void) | |
632 | { | |
2036d94a PM |
633 | struct rcu_data *rdp; |
634 | struct rcu_node *rnp; | |
c0d6d01b PM |
635 | bool ret; |
636 | ||
637 | if (in_nmi()) | |
638 | return 1; | |
639 | preempt_disable(); | |
2036d94a PM |
640 | rdp = &__get_cpu_var(rcu_sched_data); |
641 | rnp = rdp->mynode; | |
642 | ret = (rdp->grpmask & rnp->qsmaskinit) || | |
c0d6d01b PM |
643 | !rcu_scheduler_fully_active; |
644 | preempt_enable(); | |
645 | return ret; | |
646 | } | |
647 | EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); | |
648 | ||
62fde6ed | 649 | #endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */ |
9b2e4f18 | 650 | |
64db4cff | 651 | /** |
9b2e4f18 | 652 | * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle |
64db4cff | 653 | * |
9b2e4f18 PM |
654 | * If the current CPU is idle or running at a first-level (not nested) |
655 | * interrupt from idle, return true. The caller must have at least | |
656 | * disabled preemption. | |
64db4cff | 657 | */ |
9b2e4f18 | 658 | int rcu_is_cpu_rrupt_from_idle(void) |
64db4cff | 659 | { |
9b2e4f18 | 660 | return __get_cpu_var(rcu_dynticks).dynticks_nesting <= 1; |
64db4cff PM |
661 | } |
662 | ||
64db4cff PM |
663 | /* |
664 | * Snapshot the specified CPU's dynticks counter so that we can later | |
665 | * credit them with an implicit quiescent state. Return 1 if this CPU | |
1eba8f84 | 666 | * is in dynticks idle mode, which is an extended quiescent state. |
64db4cff PM |
667 | */ |
668 | static int dyntick_save_progress_counter(struct rcu_data *rdp) | |
669 | { | |
23b5c8fa | 670 | rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks); |
f0e7c19d | 671 | return (rdp->dynticks_snap & 0x1) == 0; |
64db4cff PM |
672 | } |
673 | ||
674 | /* | |
675 | * Return true if the specified CPU has passed through a quiescent | |
676 | * state by virtue of being in or having passed through an dynticks | |
677 | * idle state since the last call to dyntick_save_progress_counter() | |
678 | * for this same CPU. | |
679 | */ | |
680 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) | |
681 | { | |
7eb4f455 PM |
682 | unsigned int curr; |
683 | unsigned int snap; | |
64db4cff | 684 | |
7eb4f455 PM |
685 | curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks); |
686 | snap = (unsigned int)rdp->dynticks_snap; | |
64db4cff PM |
687 | |
688 | /* | |
689 | * If the CPU passed through or entered a dynticks idle phase with | |
690 | * no active irq/NMI handlers, then we can safely pretend that the CPU | |
691 | * already acknowledged the request to pass through a quiescent | |
692 | * state. Either way, that CPU cannot possibly be in an RCU | |
693 | * read-side critical section that started before the beginning | |
694 | * of the current RCU grace period. | |
695 | */ | |
7eb4f455 | 696 | if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) { |
d4c08f2a | 697 | trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "dti"); |
64db4cff PM |
698 | rdp->dynticks_fqs++; |
699 | return 1; | |
700 | } | |
701 | ||
702 | /* Go check for the CPU being offline. */ | |
703 | return rcu_implicit_offline_qs(rdp); | |
704 | } | |
705 | ||
13cfcca0 PM |
706 | static int jiffies_till_stall_check(void) |
707 | { | |
708 | int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout); | |
709 | ||
710 | /* | |
711 | * Limit check must be consistent with the Kconfig limits | |
712 | * for CONFIG_RCU_CPU_STALL_TIMEOUT. | |
713 | */ | |
714 | if (till_stall_check < 3) { | |
715 | ACCESS_ONCE(rcu_cpu_stall_timeout) = 3; | |
716 | till_stall_check = 3; | |
717 | } else if (till_stall_check > 300) { | |
718 | ACCESS_ONCE(rcu_cpu_stall_timeout) = 300; | |
719 | till_stall_check = 300; | |
720 | } | |
721 | return till_stall_check * HZ + RCU_STALL_DELAY_DELTA; | |
722 | } | |
723 | ||
64db4cff PM |
724 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
725 | { | |
726 | rsp->gp_start = jiffies; | |
13cfcca0 | 727 | rsp->jiffies_stall = jiffies + jiffies_till_stall_check(); |
64db4cff PM |
728 | } |
729 | ||
730 | static void print_other_cpu_stall(struct rcu_state *rsp) | |
731 | { | |
732 | int cpu; | |
733 | long delta; | |
734 | unsigned long flags; | |
285fe294 | 735 | int ndetected = 0; |
64db4cff | 736 | struct rcu_node *rnp = rcu_get_root(rsp); |
64db4cff PM |
737 | |
738 | /* Only let one CPU complain about others per time interval. */ | |
739 | ||
1304afb2 | 740 | raw_spin_lock_irqsave(&rnp->lock, flags); |
64db4cff | 741 | delta = jiffies - rsp->jiffies_stall; |
fc2219d4 | 742 | if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
1304afb2 | 743 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
744 | return; |
745 | } | |
13cfcca0 | 746 | rsp->jiffies_stall = jiffies + 3 * jiffies_till_stall_check() + 3; |
1304afb2 | 747 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 748 | |
8cdd32a9 PM |
749 | /* |
750 | * OK, time to rat on our buddy... | |
751 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
752 | * RCU CPU stall warnings. | |
753 | */ | |
a858af28 | 754 | printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks:", |
4300aa64 | 755 | rsp->name); |
a858af28 | 756 | print_cpu_stall_info_begin(); |
a0b6c9a7 | 757 | rcu_for_each_leaf_node(rsp, rnp) { |
3acd9eb3 | 758 | raw_spin_lock_irqsave(&rnp->lock, flags); |
9bc8b558 | 759 | ndetected += rcu_print_task_stall(rnp); |
3acd9eb3 | 760 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
a0b6c9a7 | 761 | if (rnp->qsmask == 0) |
64db4cff | 762 | continue; |
a0b6c9a7 | 763 | for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) |
9bc8b558 | 764 | if (rnp->qsmask & (1UL << cpu)) { |
a858af28 | 765 | print_cpu_stall_info(rsp, rnp->grplo + cpu); |
9bc8b558 PM |
766 | ndetected++; |
767 | } | |
64db4cff | 768 | } |
a858af28 PM |
769 | |
770 | /* | |
771 | * Now rat on any tasks that got kicked up to the root rcu_node | |
772 | * due to CPU offlining. | |
773 | */ | |
774 | rnp = rcu_get_root(rsp); | |
775 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
285fe294 | 776 | ndetected += rcu_print_task_stall(rnp); |
a858af28 PM |
777 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
778 | ||
779 | print_cpu_stall_info_end(); | |
780 | printk(KERN_CONT "(detected by %d, t=%ld jiffies)\n", | |
64db4cff | 781 | smp_processor_id(), (long)(jiffies - rsp->gp_start)); |
9bc8b558 PM |
782 | if (ndetected == 0) |
783 | printk(KERN_ERR "INFO: Stall ended before state dump start\n"); | |
784 | else if (!trigger_all_cpu_backtrace()) | |
4627e240 | 785 | dump_stack(); |
c1dc0b9c | 786 | |
4cdfc175 | 787 | /* Complain about tasks blocking the grace period. */ |
1ed509a2 PM |
788 | |
789 | rcu_print_detail_task_stall(rsp); | |
790 | ||
4cdfc175 | 791 | force_quiescent_state(rsp); /* Kick them all. */ |
64db4cff PM |
792 | } |
793 | ||
794 | static void print_cpu_stall(struct rcu_state *rsp) | |
795 | { | |
796 | unsigned long flags; | |
797 | struct rcu_node *rnp = rcu_get_root(rsp); | |
798 | ||
8cdd32a9 PM |
799 | /* |
800 | * OK, time to rat on ourselves... | |
801 | * See Documentation/RCU/stallwarn.txt for info on how to debug | |
802 | * RCU CPU stall warnings. | |
803 | */ | |
a858af28 PM |
804 | printk(KERN_ERR "INFO: %s self-detected stall on CPU", rsp->name); |
805 | print_cpu_stall_info_begin(); | |
806 | print_cpu_stall_info(rsp, smp_processor_id()); | |
807 | print_cpu_stall_info_end(); | |
808 | printk(KERN_CONT " (t=%lu jiffies)\n", jiffies - rsp->gp_start); | |
4627e240 PM |
809 | if (!trigger_all_cpu_backtrace()) |
810 | dump_stack(); | |
c1dc0b9c | 811 | |
1304afb2 | 812 | raw_spin_lock_irqsave(&rnp->lock, flags); |
20133cfc | 813 | if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall)) |
13cfcca0 PM |
814 | rsp->jiffies_stall = jiffies + |
815 | 3 * jiffies_till_stall_check() + 3; | |
1304afb2 | 816 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
c1dc0b9c | 817 | |
64db4cff PM |
818 | set_need_resched(); /* kick ourselves to get things going. */ |
819 | } | |
820 | ||
821 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) | |
822 | { | |
bad6e139 PM |
823 | unsigned long j; |
824 | unsigned long js; | |
64db4cff PM |
825 | struct rcu_node *rnp; |
826 | ||
742734ee | 827 | if (rcu_cpu_stall_suppress) |
c68de209 | 828 | return; |
bad6e139 PM |
829 | j = ACCESS_ONCE(jiffies); |
830 | js = ACCESS_ONCE(rsp->jiffies_stall); | |
64db4cff | 831 | rnp = rdp->mynode; |
bad6e139 | 832 | if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) { |
64db4cff PM |
833 | |
834 | /* We haven't checked in, so go dump stack. */ | |
835 | print_cpu_stall(rsp); | |
836 | ||
bad6e139 PM |
837 | } else if (rcu_gp_in_progress(rsp) && |
838 | ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) { | |
64db4cff | 839 | |
bad6e139 | 840 | /* They had a few time units to dump stack, so complain. */ |
64db4cff PM |
841 | print_other_cpu_stall(rsp); |
842 | } | |
843 | } | |
844 | ||
c68de209 PM |
845 | static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr) |
846 | { | |
742734ee | 847 | rcu_cpu_stall_suppress = 1; |
c68de209 PM |
848 | return NOTIFY_DONE; |
849 | } | |
850 | ||
53d84e00 PM |
851 | /** |
852 | * rcu_cpu_stall_reset - prevent further stall warnings in current grace period | |
853 | * | |
854 | * Set the stall-warning timeout way off into the future, thus preventing | |
855 | * any RCU CPU stall-warning messages from appearing in the current set of | |
856 | * RCU grace periods. | |
857 | * | |
858 | * The caller must disable hard irqs. | |
859 | */ | |
860 | void rcu_cpu_stall_reset(void) | |
861 | { | |
6ce75a23 PM |
862 | struct rcu_state *rsp; |
863 | ||
864 | for_each_rcu_flavor(rsp) | |
865 | rsp->jiffies_stall = jiffies + ULONG_MAX / 2; | |
53d84e00 PM |
866 | } |
867 | ||
c68de209 PM |
868 | static struct notifier_block rcu_panic_block = { |
869 | .notifier_call = rcu_panic, | |
870 | }; | |
871 | ||
872 | static void __init check_cpu_stall_init(void) | |
873 | { | |
874 | atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block); | |
875 | } | |
876 | ||
64db4cff PM |
877 | /* |
878 | * Update CPU-local rcu_data state to record the newly noticed grace period. | |
879 | * This is used both when we started the grace period and when we notice | |
9160306e PM |
880 | * that someone else started the grace period. The caller must hold the |
881 | * ->lock of the leaf rcu_node structure corresponding to the current CPU, | |
882 | * and must have irqs disabled. | |
64db4cff | 883 | */ |
9160306e PM |
884 | static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
885 | { | |
886 | if (rdp->gpnum != rnp->gpnum) { | |
121dfc4b PM |
887 | /* |
888 | * If the current grace period is waiting for this CPU, | |
889 | * set up to detect a quiescent state, otherwise don't | |
890 | * go looking for one. | |
891 | */ | |
9160306e | 892 | rdp->gpnum = rnp->gpnum; |
d4c08f2a | 893 | trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpustart"); |
121dfc4b PM |
894 | if (rnp->qsmask & rdp->grpmask) { |
895 | rdp->qs_pending = 1; | |
e4cc1f22 | 896 | rdp->passed_quiesce = 0; |
c701d5d9 | 897 | } else { |
121dfc4b | 898 | rdp->qs_pending = 0; |
c701d5d9 | 899 | } |
a858af28 | 900 | zero_cpu_stall_ticks(rdp); |
9160306e PM |
901 | } |
902 | } | |
903 | ||
64db4cff PM |
904 | static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) |
905 | { | |
9160306e PM |
906 | unsigned long flags; |
907 | struct rcu_node *rnp; | |
908 | ||
909 | local_irq_save(flags); | |
910 | rnp = rdp->mynode; | |
911 | if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */ | |
1304afb2 | 912 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
9160306e PM |
913 | local_irq_restore(flags); |
914 | return; | |
915 | } | |
916 | __note_new_gpnum(rsp, rnp, rdp); | |
1304afb2 | 917 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
918 | } |
919 | ||
920 | /* | |
921 | * Did someone else start a new RCU grace period start since we last | |
922 | * checked? Update local state appropriately if so. Must be called | |
923 | * on the CPU corresponding to rdp. | |
924 | */ | |
925 | static int | |
926 | check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp) | |
927 | { | |
928 | unsigned long flags; | |
929 | int ret = 0; | |
930 | ||
931 | local_irq_save(flags); | |
932 | if (rdp->gpnum != rsp->gpnum) { | |
933 | note_new_gpnum(rsp, rdp); | |
934 | ret = 1; | |
935 | } | |
936 | local_irq_restore(flags); | |
937 | return ret; | |
938 | } | |
939 | ||
3f5d3ea6 PM |
940 | /* |
941 | * Initialize the specified rcu_data structure's callback list to empty. | |
942 | */ | |
943 | static void init_callback_list(struct rcu_data *rdp) | |
944 | { | |
945 | int i; | |
946 | ||
947 | rdp->nxtlist = NULL; | |
948 | for (i = 0; i < RCU_NEXT_SIZE; i++) | |
949 | rdp->nxttail[i] = &rdp->nxtlist; | |
950 | } | |
951 | ||
d09b62df PM |
952 | /* |
953 | * Advance this CPU's callbacks, but only if the current grace period | |
954 | * has ended. This may be called only from the CPU to whom the rdp | |
955 | * belongs. In addition, the corresponding leaf rcu_node structure's | |
956 | * ->lock must be held by the caller, with irqs disabled. | |
957 | */ | |
958 | static void | |
959 | __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) | |
960 | { | |
961 | /* Did another grace period end? */ | |
962 | if (rdp->completed != rnp->completed) { | |
963 | ||
964 | /* Advance callbacks. No harm if list empty. */ | |
965 | rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL]; | |
966 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL]; | |
967 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; | |
968 | ||
969 | /* Remember that we saw this grace-period completion. */ | |
970 | rdp->completed = rnp->completed; | |
d4c08f2a | 971 | trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuend"); |
20377f32 | 972 | |
5ff8e6f0 FW |
973 | /* |
974 | * If we were in an extended quiescent state, we may have | |
121dfc4b | 975 | * missed some grace periods that others CPUs handled on |
5ff8e6f0 | 976 | * our behalf. Catch up with this state to avoid noting |
121dfc4b PM |
977 | * spurious new grace periods. If another grace period |
978 | * has started, then rnp->gpnum will have advanced, so | |
979 | * we will detect this later on. | |
5ff8e6f0 | 980 | */ |
121dfc4b | 981 | if (ULONG_CMP_LT(rdp->gpnum, rdp->completed)) |
5ff8e6f0 FW |
982 | rdp->gpnum = rdp->completed; |
983 | ||
20377f32 | 984 | /* |
121dfc4b PM |
985 | * If RCU does not need a quiescent state from this CPU, |
986 | * then make sure that this CPU doesn't go looking for one. | |
20377f32 | 987 | */ |
121dfc4b | 988 | if ((rnp->qsmask & rdp->grpmask) == 0) |
20377f32 | 989 | rdp->qs_pending = 0; |
d09b62df PM |
990 | } |
991 | } | |
992 | ||
993 | /* | |
994 | * Advance this CPU's callbacks, but only if the current grace period | |
995 | * has ended. This may be called only from the CPU to whom the rdp | |
996 | * belongs. | |
997 | */ | |
998 | static void | |
999 | rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) | |
1000 | { | |
1001 | unsigned long flags; | |
1002 | struct rcu_node *rnp; | |
1003 | ||
1004 | local_irq_save(flags); | |
1005 | rnp = rdp->mynode; | |
1006 | if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */ | |
1304afb2 | 1007 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
d09b62df PM |
1008 | local_irq_restore(flags); |
1009 | return; | |
1010 | } | |
1011 | __rcu_process_gp_end(rsp, rnp, rdp); | |
1304afb2 | 1012 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
d09b62df PM |
1013 | } |
1014 | ||
1015 | /* | |
1016 | * Do per-CPU grace-period initialization for running CPU. The caller | |
1017 | * must hold the lock of the leaf rcu_node structure corresponding to | |
1018 | * this CPU. | |
1019 | */ | |
1020 | static void | |
1021 | rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) | |
1022 | { | |
1023 | /* Prior grace period ended, so advance callbacks for current CPU. */ | |
1024 | __rcu_process_gp_end(rsp, rnp, rdp); | |
1025 | ||
9160306e PM |
1026 | /* Set state so that this CPU will detect the next quiescent state. */ |
1027 | __note_new_gpnum(rsp, rnp, rdp); | |
d09b62df PM |
1028 | } |
1029 | ||
b3dbec76 | 1030 | /* |
7fdefc10 | 1031 | * Initialize a new grace period. |
b3dbec76 | 1032 | */ |
7fdefc10 | 1033 | static int rcu_gp_init(struct rcu_state *rsp) |
b3dbec76 PM |
1034 | { |
1035 | struct rcu_data *rdp; | |
7fdefc10 | 1036 | struct rcu_node *rnp = rcu_get_root(rsp); |
b3dbec76 | 1037 | |
7fdefc10 | 1038 | raw_spin_lock_irq(&rnp->lock); |
4cdfc175 | 1039 | rsp->gp_flags = 0; /* Clear all flags: New grace period. */ |
b3dbec76 | 1040 | |
7fdefc10 PM |
1041 | if (rcu_gp_in_progress(rsp)) { |
1042 | /* Grace period already in progress, don't start another. */ | |
1043 | raw_spin_unlock_irq(&rnp->lock); | |
1044 | return 0; | |
1045 | } | |
1046 | ||
7fdefc10 PM |
1047 | /* Advance to a new grace period and initialize state. */ |
1048 | rsp->gpnum++; | |
1049 | trace_rcu_grace_period(rsp->name, rsp->gpnum, "start"); | |
7fdefc10 PM |
1050 | record_gp_stall_check_time(rsp); |
1051 | raw_spin_unlock_irq(&rnp->lock); | |
1052 | ||
1053 | /* Exclude any concurrent CPU-hotplug operations. */ | |
1054 | get_online_cpus(); | |
1055 | ||
1056 | /* | |
1057 | * Set the quiescent-state-needed bits in all the rcu_node | |
1058 | * structures for all currently online CPUs in breadth-first order, | |
1059 | * starting from the root rcu_node structure, relying on the layout | |
1060 | * of the tree within the rsp->node[] array. Note that other CPUs | |
1061 | * will access only the leaves of the hierarchy, thus seeing that no | |
1062 | * grace period is in progress, at least until the corresponding | |
1063 | * leaf node has been initialized. In addition, we have excluded | |
1064 | * CPU-hotplug operations. | |
1065 | * | |
1066 | * The grace period cannot complete until the initialization | |
1067 | * process finishes, because this kthread handles both. | |
1068 | */ | |
1069 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
b3dbec76 | 1070 | raw_spin_lock_irq(&rnp->lock); |
b3dbec76 | 1071 | rdp = this_cpu_ptr(rsp->rda); |
7fdefc10 PM |
1072 | rcu_preempt_check_blocked_tasks(rnp); |
1073 | rnp->qsmask = rnp->qsmaskinit; | |
1074 | rnp->gpnum = rsp->gpnum; | |
1075 | rnp->completed = rsp->completed; | |
1076 | if (rnp == rdp->mynode) | |
1077 | rcu_start_gp_per_cpu(rsp, rnp, rdp); | |
1078 | rcu_preempt_boost_start_gp(rnp); | |
1079 | trace_rcu_grace_period_init(rsp->name, rnp->gpnum, | |
1080 | rnp->level, rnp->grplo, | |
1081 | rnp->grphi, rnp->qsmask); | |
1082 | raw_spin_unlock_irq(&rnp->lock); | |
1083 | cond_resched(); | |
1084 | } | |
b3dbec76 | 1085 | |
7fdefc10 PM |
1086 | put_online_cpus(); |
1087 | return 1; | |
1088 | } | |
b3dbec76 | 1089 | |
4cdfc175 PM |
1090 | /* |
1091 | * Do one round of quiescent-state forcing. | |
1092 | */ | |
1093 | int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in) | |
1094 | { | |
1095 | int fqs_state = fqs_state_in; | |
1096 | struct rcu_node *rnp = rcu_get_root(rsp); | |
1097 | ||
1098 | rsp->n_force_qs++; | |
1099 | if (fqs_state == RCU_SAVE_DYNTICK) { | |
1100 | /* Collect dyntick-idle snapshots. */ | |
1101 | force_qs_rnp(rsp, dyntick_save_progress_counter); | |
1102 | fqs_state = RCU_FORCE_QS; | |
1103 | } else { | |
1104 | /* Handle dyntick-idle and offline CPUs. */ | |
1105 | force_qs_rnp(rsp, rcu_implicit_dynticks_qs); | |
1106 | } | |
1107 | /* Clear flag to prevent immediate re-entry. */ | |
1108 | if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { | |
1109 | raw_spin_lock_irq(&rnp->lock); | |
1110 | rsp->gp_flags &= ~RCU_GP_FLAG_FQS; | |
1111 | raw_spin_unlock_irq(&rnp->lock); | |
1112 | } | |
1113 | return fqs_state; | |
1114 | } | |
1115 | ||
7fdefc10 PM |
1116 | /* |
1117 | * Clean up after the old grace period. | |
1118 | */ | |
4cdfc175 | 1119 | static void rcu_gp_cleanup(struct rcu_state *rsp) |
7fdefc10 PM |
1120 | { |
1121 | unsigned long gp_duration; | |
1122 | struct rcu_data *rdp; | |
1123 | struct rcu_node *rnp = rcu_get_root(rsp); | |
b3dbec76 | 1124 | |
7fdefc10 PM |
1125 | raw_spin_lock_irq(&rnp->lock); |
1126 | gp_duration = jiffies - rsp->gp_start; | |
1127 | if (gp_duration > rsp->gp_max) | |
1128 | rsp->gp_max = gp_duration; | |
b3dbec76 | 1129 | |
7fdefc10 PM |
1130 | /* |
1131 | * We know the grace period is complete, but to everyone else | |
1132 | * it appears to still be ongoing. But it is also the case | |
1133 | * that to everyone else it looks like there is nothing that | |
1134 | * they can do to advance the grace period. It is therefore | |
1135 | * safe for us to drop the lock in order to mark the grace | |
1136 | * period as completed in all of the rcu_node structures. | |
1137 | * | |
1138 | * But if this CPU needs another grace period, it will take | |
1139 | * care of this while initializing the next grace period. | |
1140 | * We use RCU_WAIT_TAIL instead of the usual RCU_DONE_TAIL | |
1141 | * because the callbacks have not yet been advanced: Those | |
1142 | * callbacks are waiting on the grace period that just now | |
1143 | * completed. | |
1144 | */ | |
1145 | rdp = this_cpu_ptr(rsp->rda); | |
1146 | if (*rdp->nxttail[RCU_WAIT_TAIL] == NULL) { | |
1147 | raw_spin_unlock_irq(&rnp->lock); | |
b3dbec76 PM |
1148 | |
1149 | /* | |
7fdefc10 PM |
1150 | * Propagate new ->completed value to rcu_node |
1151 | * structures so that other CPUs don't have to | |
1152 | * wait until the start of the next grace period | |
1153 | * to process their callbacks. | |
b3dbec76 PM |
1154 | */ |
1155 | rcu_for_each_node_breadth_first(rsp, rnp) { | |
755609a9 | 1156 | raw_spin_lock_irq(&rnp->lock); |
7fdefc10 | 1157 | rnp->completed = rsp->gpnum; |
755609a9 PM |
1158 | raw_spin_unlock_irq(&rnp->lock); |
1159 | cond_resched(); | |
b3dbec76 | 1160 | } |
b3dbec76 | 1161 | rnp = rcu_get_root(rsp); |
755609a9 | 1162 | raw_spin_lock_irq(&rnp->lock); |
7fdefc10 PM |
1163 | } |
1164 | ||
1165 | rsp->completed = rsp->gpnum; /* Declare grace period done. */ | |
1166 | trace_rcu_grace_period(rsp->name, rsp->completed, "end"); | |
1167 | rsp->fqs_state = RCU_GP_IDLE; | |
1168 | if (cpu_needs_another_gp(rsp, rdp)) | |
1169 | rsp->gp_flags = 1; | |
1170 | raw_spin_unlock_irq(&rnp->lock); | |
7fdefc10 PM |
1171 | } |
1172 | ||
1173 | /* | |
1174 | * Body of kthread that handles grace periods. | |
1175 | */ | |
1176 | static int __noreturn rcu_gp_kthread(void *arg) | |
1177 | { | |
4cdfc175 PM |
1178 | int fqs_state; |
1179 | int ret; | |
7fdefc10 PM |
1180 | struct rcu_state *rsp = arg; |
1181 | struct rcu_node *rnp = rcu_get_root(rsp); | |
1182 | ||
1183 | for (;;) { | |
1184 | ||
1185 | /* Handle grace-period start. */ | |
1186 | for (;;) { | |
4cdfc175 PM |
1187 | wait_event_interruptible(rsp->gp_wq, |
1188 | rsp->gp_flags & | |
1189 | RCU_GP_FLAG_INIT); | |
1190 | if ((rsp->gp_flags & RCU_GP_FLAG_INIT) && | |
1191 | rcu_gp_init(rsp)) | |
7fdefc10 PM |
1192 | break; |
1193 | cond_resched(); | |
1194 | flush_signals(current); | |
1195 | } | |
cabc49c1 | 1196 | |
4cdfc175 PM |
1197 | /* Handle quiescent-state forcing. */ |
1198 | fqs_state = RCU_SAVE_DYNTICK; | |
cabc49c1 | 1199 | for (;;) { |
4cdfc175 PM |
1200 | rsp->jiffies_force_qs = jiffies + |
1201 | RCU_JIFFIES_TILL_FORCE_QS; | |
1202 | ret = wait_event_interruptible_timeout(rsp->gp_wq, | |
1203 | (rsp->gp_flags & RCU_GP_FLAG_FQS) || | |
1204 | (!ACCESS_ONCE(rnp->qsmask) && | |
1205 | !rcu_preempt_blocked_readers_cgp(rnp)), | |
1206 | RCU_JIFFIES_TILL_FORCE_QS); | |
1207 | /* If grace period done, leave loop. */ | |
cabc49c1 | 1208 | if (!ACCESS_ONCE(rnp->qsmask) && |
4cdfc175 | 1209 | !rcu_preempt_blocked_readers_cgp(rnp)) |
cabc49c1 | 1210 | break; |
4cdfc175 PM |
1211 | /* If time for quiescent-state forcing, do it. */ |
1212 | if (ret == 0 || (rsp->gp_flags & RCU_GP_FLAG_FQS)) { | |
1213 | fqs_state = rcu_gp_fqs(rsp, fqs_state); | |
1214 | cond_resched(); | |
1215 | } else { | |
1216 | /* Deal with stray signal. */ | |
1217 | cond_resched(); | |
1218 | flush_signals(current); | |
1219 | } | |
cabc49c1 | 1220 | } |
4cdfc175 PM |
1221 | |
1222 | /* Handle grace-period end. */ | |
1223 | rcu_gp_cleanup(rsp); | |
b3dbec76 | 1224 | } |
b3dbec76 PM |
1225 | } |
1226 | ||
64db4cff PM |
1227 | /* |
1228 | * Start a new RCU grace period if warranted, re-initializing the hierarchy | |
1229 | * in preparation for detecting the next grace period. The caller must hold | |
1230 | * the root node's ->lock, which is released before return. Hard irqs must | |
1231 | * be disabled. | |
e5601400 PM |
1232 | * |
1233 | * Note that it is legal for a dying CPU (which is marked as offline) to | |
1234 | * invoke this function. This can happen when the dying CPU reports its | |
1235 | * quiescent state. | |
64db4cff PM |
1236 | */ |
1237 | static void | |
1238 | rcu_start_gp(struct rcu_state *rsp, unsigned long flags) | |
1239 | __releases(rcu_get_root(rsp)->lock) | |
1240 | { | |
394f99a9 | 1241 | struct rcu_data *rdp = this_cpu_ptr(rsp->rda); |
64db4cff | 1242 | struct rcu_node *rnp = rcu_get_root(rsp); |
64db4cff | 1243 | |
b3dbec76 | 1244 | if (!rsp->gp_kthread || |
afe24b12 PM |
1245 | !cpu_needs_another_gp(rsp, rdp)) { |
1246 | /* | |
b3dbec76 PM |
1247 | * Either we have not yet spawned the grace-period |
1248 | * task or this CPU does not need another grace period. | |
1249 | * Either way, don't start a new grace period. | |
afe24b12 PM |
1250 | */ |
1251 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
1252 | return; | |
1253 | } | |
b32e9eb6 | 1254 | |
4cdfc175 | 1255 | rsp->gp_flags = RCU_GP_FLAG_INIT; |
b3dbec76 PM |
1256 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1257 | wake_up(&rsp->gp_wq); | |
64db4cff PM |
1258 | } |
1259 | ||
f41d911f | 1260 | /* |
d3f6bad3 PM |
1261 | * Report a full set of quiescent states to the specified rcu_state |
1262 | * data structure. This involves cleaning up after the prior grace | |
1263 | * period and letting rcu_start_gp() start up the next grace period | |
1264 | * if one is needed. Note that the caller must hold rnp->lock, as | |
1265 | * required by rcu_start_gp(), which will release it. | |
f41d911f | 1266 | */ |
d3f6bad3 | 1267 | static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) |
fc2219d4 | 1268 | __releases(rcu_get_root(rsp)->lock) |
f41d911f | 1269 | { |
fc2219d4 | 1270 | WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
cabc49c1 PM |
1271 | raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags); |
1272 | wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */ | |
f41d911f PM |
1273 | } |
1274 | ||
64db4cff | 1275 | /* |
d3f6bad3 PM |
1276 | * Similar to rcu_report_qs_rdp(), for which it is a helper function. |
1277 | * Allows quiescent states for a group of CPUs to be reported at one go | |
1278 | * to the specified rcu_node structure, though all the CPUs in the group | |
1279 | * must be represented by the same rcu_node structure (which need not be | |
1280 | * a leaf rcu_node structure, though it often will be). That structure's | |
1281 | * lock must be held upon entry, and it is released before return. | |
64db4cff PM |
1282 | */ |
1283 | static void | |
d3f6bad3 PM |
1284 | rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, |
1285 | struct rcu_node *rnp, unsigned long flags) | |
64db4cff PM |
1286 | __releases(rnp->lock) |
1287 | { | |
28ecd580 PM |
1288 | struct rcu_node *rnp_c; |
1289 | ||
64db4cff PM |
1290 | /* Walk up the rcu_node hierarchy. */ |
1291 | for (;;) { | |
1292 | if (!(rnp->qsmask & mask)) { | |
1293 | ||
1294 | /* Our bit has already been cleared, so done. */ | |
1304afb2 | 1295 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1296 | return; |
1297 | } | |
1298 | rnp->qsmask &= ~mask; | |
d4c08f2a PM |
1299 | trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum, |
1300 | mask, rnp->qsmask, rnp->level, | |
1301 | rnp->grplo, rnp->grphi, | |
1302 | !!rnp->gp_tasks); | |
27f4d280 | 1303 | if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { |
64db4cff PM |
1304 | |
1305 | /* Other bits still set at this level, so done. */ | |
1304afb2 | 1306 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1307 | return; |
1308 | } | |
1309 | mask = rnp->grpmask; | |
1310 | if (rnp->parent == NULL) { | |
1311 | ||
1312 | /* No more levels. Exit loop holding root lock. */ | |
1313 | ||
1314 | break; | |
1315 | } | |
1304afb2 | 1316 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
28ecd580 | 1317 | rnp_c = rnp; |
64db4cff | 1318 | rnp = rnp->parent; |
1304afb2 | 1319 | raw_spin_lock_irqsave(&rnp->lock, flags); |
28ecd580 | 1320 | WARN_ON_ONCE(rnp_c->qsmask); |
64db4cff PM |
1321 | } |
1322 | ||
1323 | /* | |
1324 | * Get here if we are the last CPU to pass through a quiescent | |
d3f6bad3 | 1325 | * state for this grace period. Invoke rcu_report_qs_rsp() |
f41d911f | 1326 | * to clean up and start the next grace period if one is needed. |
64db4cff | 1327 | */ |
d3f6bad3 | 1328 | rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ |
64db4cff PM |
1329 | } |
1330 | ||
1331 | /* | |
d3f6bad3 PM |
1332 | * Record a quiescent state for the specified CPU to that CPU's rcu_data |
1333 | * structure. This must be either called from the specified CPU, or | |
1334 | * called when the specified CPU is known to be offline (and when it is | |
1335 | * also known that no other CPU is concurrently trying to help the offline | |
1336 | * CPU). The lastcomp argument is used to make sure we are still in the | |
1337 | * grace period of interest. We don't want to end the current grace period | |
1338 | * based on quiescent states detected in an earlier grace period! | |
64db4cff PM |
1339 | */ |
1340 | static void | |
e4cc1f22 | 1341 | rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastgp) |
64db4cff PM |
1342 | { |
1343 | unsigned long flags; | |
1344 | unsigned long mask; | |
1345 | struct rcu_node *rnp; | |
1346 | ||
1347 | rnp = rdp->mynode; | |
1304afb2 | 1348 | raw_spin_lock_irqsave(&rnp->lock, flags); |
e4cc1f22 | 1349 | if (lastgp != rnp->gpnum || rnp->completed == rnp->gpnum) { |
64db4cff PM |
1350 | |
1351 | /* | |
e4cc1f22 PM |
1352 | * The grace period in which this quiescent state was |
1353 | * recorded has ended, so don't report it upwards. | |
1354 | * We will instead need a new quiescent state that lies | |
1355 | * within the current grace period. | |
64db4cff | 1356 | */ |
e4cc1f22 | 1357 | rdp->passed_quiesce = 0; /* need qs for new gp. */ |
1304afb2 | 1358 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1359 | return; |
1360 | } | |
1361 | mask = rdp->grpmask; | |
1362 | if ((rnp->qsmask & mask) == 0) { | |
1304afb2 | 1363 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff PM |
1364 | } else { |
1365 | rdp->qs_pending = 0; | |
1366 | ||
1367 | /* | |
1368 | * This GP can't end until cpu checks in, so all of our | |
1369 | * callbacks can be processed during the next GP. | |
1370 | */ | |
64db4cff PM |
1371 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
1372 | ||
d3f6bad3 | 1373 | rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */ |
64db4cff PM |
1374 | } |
1375 | } | |
1376 | ||
1377 | /* | |
1378 | * Check to see if there is a new grace period of which this CPU | |
1379 | * is not yet aware, and if so, set up local rcu_data state for it. | |
1380 | * Otherwise, see if this CPU has just passed through its first | |
1381 | * quiescent state for this grace period, and record that fact if so. | |
1382 | */ | |
1383 | static void | |
1384 | rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) | |
1385 | { | |
1386 | /* If there is now a new grace period, record and return. */ | |
1387 | if (check_for_new_grace_period(rsp, rdp)) | |
1388 | return; | |
1389 | ||
1390 | /* | |
1391 | * Does this CPU still need to do its part for current grace period? | |
1392 | * If no, return and let the other CPUs do their part as well. | |
1393 | */ | |
1394 | if (!rdp->qs_pending) | |
1395 | return; | |
1396 | ||
1397 | /* | |
1398 | * Was there a quiescent state since the beginning of the grace | |
1399 | * period? If no, then exit and wait for the next call. | |
1400 | */ | |
e4cc1f22 | 1401 | if (!rdp->passed_quiesce) |
64db4cff PM |
1402 | return; |
1403 | ||
d3f6bad3 PM |
1404 | /* |
1405 | * Tell RCU we are done (but rcu_report_qs_rdp() will be the | |
1406 | * judge of that). | |
1407 | */ | |
e4cc1f22 | 1408 | rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesce_gpnum); |
64db4cff PM |
1409 | } |
1410 | ||
1411 | #ifdef CONFIG_HOTPLUG_CPU | |
1412 | ||
e74f4c45 | 1413 | /* |
b1420f1c PM |
1414 | * Send the specified CPU's RCU callbacks to the orphanage. The |
1415 | * specified CPU must be offline, and the caller must hold the | |
1416 | * ->onofflock. | |
e74f4c45 | 1417 | */ |
b1420f1c PM |
1418 | static void |
1419 | rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp, | |
1420 | struct rcu_node *rnp, struct rcu_data *rdp) | |
e74f4c45 | 1421 | { |
b1420f1c PM |
1422 | /* |
1423 | * Orphan the callbacks. First adjust the counts. This is safe | |
1424 | * because ->onofflock excludes _rcu_barrier()'s adoption of | |
1425 | * the callbacks, thus no memory barrier is required. | |
1426 | */ | |
a50c3af9 | 1427 | if (rdp->nxtlist != NULL) { |
b1420f1c PM |
1428 | rsp->qlen_lazy += rdp->qlen_lazy; |
1429 | rsp->qlen += rdp->qlen; | |
1430 | rdp->n_cbs_orphaned += rdp->qlen; | |
a50c3af9 | 1431 | rdp->qlen_lazy = 0; |
1d1fb395 | 1432 | ACCESS_ONCE(rdp->qlen) = 0; |
a50c3af9 PM |
1433 | } |
1434 | ||
1435 | /* | |
b1420f1c PM |
1436 | * Next, move those callbacks still needing a grace period to |
1437 | * the orphanage, where some other CPU will pick them up. | |
1438 | * Some of the callbacks might have gone partway through a grace | |
1439 | * period, but that is too bad. They get to start over because we | |
1440 | * cannot assume that grace periods are synchronized across CPUs. | |
1441 | * We don't bother updating the ->nxttail[] array yet, instead | |
1442 | * we just reset the whole thing later on. | |
a50c3af9 | 1443 | */ |
b1420f1c PM |
1444 | if (*rdp->nxttail[RCU_DONE_TAIL] != NULL) { |
1445 | *rsp->orphan_nxttail = *rdp->nxttail[RCU_DONE_TAIL]; | |
1446 | rsp->orphan_nxttail = rdp->nxttail[RCU_NEXT_TAIL]; | |
1447 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
a50c3af9 PM |
1448 | } |
1449 | ||
1450 | /* | |
b1420f1c PM |
1451 | * Then move the ready-to-invoke callbacks to the orphanage, |
1452 | * where some other CPU will pick them up. These will not be | |
1453 | * required to pass though another grace period: They are done. | |
a50c3af9 | 1454 | */ |
e5601400 | 1455 | if (rdp->nxtlist != NULL) { |
b1420f1c PM |
1456 | *rsp->orphan_donetail = rdp->nxtlist; |
1457 | rsp->orphan_donetail = rdp->nxttail[RCU_DONE_TAIL]; | |
e5601400 | 1458 | } |
e74f4c45 | 1459 | |
b1420f1c | 1460 | /* Finally, initialize the rcu_data structure's list to empty. */ |
3f5d3ea6 | 1461 | init_callback_list(rdp); |
b1420f1c PM |
1462 | } |
1463 | ||
1464 | /* | |
1465 | * Adopt the RCU callbacks from the specified rcu_state structure's | |
1466 | * orphanage. The caller must hold the ->onofflock. | |
1467 | */ | |
1468 | static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) | |
1469 | { | |
1470 | int i; | |
1471 | struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); | |
1472 | ||
a50c3af9 | 1473 | /* |
b1420f1c PM |
1474 | * If there is an rcu_barrier() operation in progress, then |
1475 | * only the task doing that operation is permitted to adopt | |
1476 | * callbacks. To do otherwise breaks rcu_barrier() and friends | |
1477 | * by causing them to fail to wait for the callbacks in the | |
1478 | * orphanage. | |
a50c3af9 | 1479 | */ |
b1420f1c PM |
1480 | if (rsp->rcu_barrier_in_progress && |
1481 | rsp->rcu_barrier_in_progress != current) | |
1482 | return; | |
1483 | ||
1484 | /* Do the accounting first. */ | |
1485 | rdp->qlen_lazy += rsp->qlen_lazy; | |
1486 | rdp->qlen += rsp->qlen; | |
1487 | rdp->n_cbs_adopted += rsp->qlen; | |
8f5af6f1 PM |
1488 | if (rsp->qlen_lazy != rsp->qlen) |
1489 | rcu_idle_count_callbacks_posted(); | |
b1420f1c PM |
1490 | rsp->qlen_lazy = 0; |
1491 | rsp->qlen = 0; | |
1492 | ||
1493 | /* | |
1494 | * We do not need a memory barrier here because the only way we | |
1495 | * can get here if there is an rcu_barrier() in flight is if | |
1496 | * we are the task doing the rcu_barrier(). | |
1497 | */ | |
1498 | ||
1499 | /* First adopt the ready-to-invoke callbacks. */ | |
1500 | if (rsp->orphan_donelist != NULL) { | |
1501 | *rsp->orphan_donetail = *rdp->nxttail[RCU_DONE_TAIL]; | |
1502 | *rdp->nxttail[RCU_DONE_TAIL] = rsp->orphan_donelist; | |
1503 | for (i = RCU_NEXT_SIZE - 1; i >= RCU_DONE_TAIL; i--) | |
1504 | if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) | |
1505 | rdp->nxttail[i] = rsp->orphan_donetail; | |
1506 | rsp->orphan_donelist = NULL; | |
1507 | rsp->orphan_donetail = &rsp->orphan_donelist; | |
1508 | } | |
1509 | ||
1510 | /* And then adopt the callbacks that still need a grace period. */ | |
1511 | if (rsp->orphan_nxtlist != NULL) { | |
1512 | *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxtlist; | |
1513 | rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxttail; | |
1514 | rsp->orphan_nxtlist = NULL; | |
1515 | rsp->orphan_nxttail = &rsp->orphan_nxtlist; | |
1516 | } | |
1517 | } | |
1518 | ||
1519 | /* | |
1520 | * Trace the fact that this CPU is going offline. | |
1521 | */ | |
1522 | static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) | |
1523 | { | |
1524 | RCU_TRACE(unsigned long mask); | |
1525 | RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda)); | |
1526 | RCU_TRACE(struct rcu_node *rnp = rdp->mynode); | |
1527 | ||
1528 | RCU_TRACE(mask = rdp->grpmask); | |
e5601400 PM |
1529 | trace_rcu_grace_period(rsp->name, |
1530 | rnp->gpnum + 1 - !!(rnp->qsmask & mask), | |
1531 | "cpuofl"); | |
64db4cff PM |
1532 | } |
1533 | ||
1534 | /* | |
e5601400 | 1535 | * The CPU has been completely removed, and some other CPU is reporting |
b1420f1c PM |
1536 | * this fact from process context. Do the remainder of the cleanup, |
1537 | * including orphaning the outgoing CPU's RCU callbacks, and also | |
1538 | * adopting them, if there is no _rcu_barrier() instance running. | |
e5601400 PM |
1539 | * There can only be one CPU hotplug operation at a time, so no other |
1540 | * CPU can be attempting to update rcu_cpu_kthread_task. | |
64db4cff | 1541 | */ |
e5601400 | 1542 | static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) |
64db4cff | 1543 | { |
2036d94a PM |
1544 | unsigned long flags; |
1545 | unsigned long mask; | |
1546 | int need_report = 0; | |
e5601400 | 1547 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
b1420f1c | 1548 | struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ |
e5601400 | 1549 | |
2036d94a | 1550 | /* Adjust any no-longer-needed kthreads. */ |
e5601400 PM |
1551 | rcu_stop_cpu_kthread(cpu); |
1552 | rcu_node_kthread_setaffinity(rnp, -1); | |
2036d94a | 1553 | |
b1420f1c | 1554 | /* Remove the dead CPU from the bitmasks in the rcu_node hierarchy. */ |
2036d94a PM |
1555 | |
1556 | /* Exclude any attempts to start a new grace period. */ | |
1557 | raw_spin_lock_irqsave(&rsp->onofflock, flags); | |
1558 | ||
b1420f1c PM |
1559 | /* Orphan the dead CPU's callbacks, and adopt them if appropriate. */ |
1560 | rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp); | |
1561 | rcu_adopt_orphan_cbs(rsp); | |
1562 | ||
2036d94a PM |
1563 | /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ |
1564 | mask = rdp->grpmask; /* rnp->grplo is constant. */ | |
1565 | do { | |
1566 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ | |
1567 | rnp->qsmaskinit &= ~mask; | |
1568 | if (rnp->qsmaskinit != 0) { | |
1569 | if (rnp != rdp->mynode) | |
1570 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
1571 | break; | |
1572 | } | |
1573 | if (rnp == rdp->mynode) | |
1574 | need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp); | |
1575 | else | |
1576 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ | |
1577 | mask = rnp->grpmask; | |
1578 | rnp = rnp->parent; | |
1579 | } while (rnp != NULL); | |
1580 | ||
1581 | /* | |
1582 | * We still hold the leaf rcu_node structure lock here, and | |
1583 | * irqs are still disabled. The reason for this subterfuge is | |
1584 | * because invoking rcu_report_unblock_qs_rnp() with ->onofflock | |
1585 | * held leads to deadlock. | |
1586 | */ | |
1587 | raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ | |
1588 | rnp = rdp->mynode; | |
1589 | if (need_report & RCU_OFL_TASKS_NORM_GP) | |
1590 | rcu_report_unblock_qs_rnp(rnp, flags); | |
1591 | else | |
1592 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
1593 | if (need_report & RCU_OFL_TASKS_EXP_GP) | |
1594 | rcu_report_exp_rnp(rsp, rnp, true); | |
cf01537e PM |
1595 | WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL, |
1596 | "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n", | |
1597 | cpu, rdp->qlen, rdp->nxtlist); | |
64db4cff PM |
1598 | } |
1599 | ||
1600 | #else /* #ifdef CONFIG_HOTPLUG_CPU */ | |
1601 | ||
b1420f1c PM |
1602 | static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) |
1603 | { | |
1604 | } | |
1605 | ||
e5601400 | 1606 | static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) |
e74f4c45 PM |
1607 | { |
1608 | } | |
1609 | ||
e5601400 | 1610 | static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) |
64db4cff PM |
1611 | { |
1612 | } | |
1613 | ||
1614 | #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ | |
1615 | ||
1616 | /* | |
1617 | * Invoke any RCU callbacks that have made it to the end of their grace | |
1618 | * period. Thottle as specified by rdp->blimit. | |
1619 | */ | |
37c72e56 | 1620 | static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) |
64db4cff PM |
1621 | { |
1622 | unsigned long flags; | |
1623 | struct rcu_head *next, *list, **tail; | |
b41772ab | 1624 | int bl, count, count_lazy, i; |
64db4cff PM |
1625 | |
1626 | /* If no callbacks are ready, just return.*/ | |
29c00b4a | 1627 | if (!cpu_has_callbacks_ready_to_invoke(rdp)) { |
486e2593 | 1628 | trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0); |
4968c300 PM |
1629 | trace_rcu_batch_end(rsp->name, 0, !!ACCESS_ONCE(rdp->nxtlist), |
1630 | need_resched(), is_idle_task(current), | |
1631 | rcu_is_callbacks_kthread()); | |
64db4cff | 1632 | return; |
29c00b4a | 1633 | } |
64db4cff PM |
1634 | |
1635 | /* | |
1636 | * Extract the list of ready callbacks, disabling to prevent | |
1637 | * races with call_rcu() from interrupt handlers. | |
1638 | */ | |
1639 | local_irq_save(flags); | |
8146c4e2 | 1640 | WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); |
29c00b4a | 1641 | bl = rdp->blimit; |
486e2593 | 1642 | trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl); |
64db4cff PM |
1643 | list = rdp->nxtlist; |
1644 | rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; | |
1645 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; | |
1646 | tail = rdp->nxttail[RCU_DONE_TAIL]; | |
b41772ab PM |
1647 | for (i = RCU_NEXT_SIZE - 1; i >= 0; i--) |
1648 | if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) | |
1649 | rdp->nxttail[i] = &rdp->nxtlist; | |
64db4cff PM |
1650 | local_irq_restore(flags); |
1651 | ||
1652 | /* Invoke callbacks. */ | |
486e2593 | 1653 | count = count_lazy = 0; |
64db4cff PM |
1654 | while (list) { |
1655 | next = list->next; | |
1656 | prefetch(next); | |
551d55a9 | 1657 | debug_rcu_head_unqueue(list); |
486e2593 PM |
1658 | if (__rcu_reclaim(rsp->name, list)) |
1659 | count_lazy++; | |
64db4cff | 1660 | list = next; |
dff1672d PM |
1661 | /* Stop only if limit reached and CPU has something to do. */ |
1662 | if (++count >= bl && | |
1663 | (need_resched() || | |
1664 | (!is_idle_task(current) && !rcu_is_callbacks_kthread()))) | |
64db4cff PM |
1665 | break; |
1666 | } | |
1667 | ||
1668 | local_irq_save(flags); | |
4968c300 PM |
1669 | trace_rcu_batch_end(rsp->name, count, !!list, need_resched(), |
1670 | is_idle_task(current), | |
1671 | rcu_is_callbacks_kthread()); | |
64db4cff PM |
1672 | |
1673 | /* Update count, and requeue any remaining callbacks. */ | |
64db4cff PM |
1674 | if (list != NULL) { |
1675 | *tail = rdp->nxtlist; | |
1676 | rdp->nxtlist = list; | |
b41772ab PM |
1677 | for (i = 0; i < RCU_NEXT_SIZE; i++) |
1678 | if (&rdp->nxtlist == rdp->nxttail[i]) | |
1679 | rdp->nxttail[i] = tail; | |
64db4cff PM |
1680 | else |
1681 | break; | |
1682 | } | |
b1420f1c PM |
1683 | smp_mb(); /* List handling before counting for rcu_barrier(). */ |
1684 | rdp->qlen_lazy -= count_lazy; | |
1d1fb395 | 1685 | ACCESS_ONCE(rdp->qlen) -= count; |
b1420f1c | 1686 | rdp->n_cbs_invoked += count; |
64db4cff PM |
1687 | |
1688 | /* Reinstate batch limit if we have worked down the excess. */ | |
1689 | if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) | |
1690 | rdp->blimit = blimit; | |
1691 | ||
37c72e56 PM |
1692 | /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
1693 | if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { | |
1694 | rdp->qlen_last_fqs_check = 0; | |
1695 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
1696 | } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) | |
1697 | rdp->qlen_last_fqs_check = rdp->qlen; | |
cfca9279 | 1698 | WARN_ON_ONCE((rdp->nxtlist == NULL) != (rdp->qlen == 0)); |
37c72e56 | 1699 | |
64db4cff PM |
1700 | local_irq_restore(flags); |
1701 | ||
e0f23060 | 1702 | /* Re-invoke RCU core processing if there are callbacks remaining. */ |
64db4cff | 1703 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
a46e0899 | 1704 | invoke_rcu_core(); |
64db4cff PM |
1705 | } |
1706 | ||
1707 | /* | |
1708 | * Check to see if this CPU is in a non-context-switch quiescent state | |
1709 | * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). | |
e0f23060 | 1710 | * Also schedule RCU core processing. |
64db4cff | 1711 | * |
9b2e4f18 | 1712 | * This function must be called from hardirq context. It is normally |
64db4cff PM |
1713 | * invoked from the scheduling-clock interrupt. If rcu_pending returns |
1714 | * false, there is no point in invoking rcu_check_callbacks(). | |
1715 | */ | |
1716 | void rcu_check_callbacks(int cpu, int user) | |
1717 | { | |
300df91c | 1718 | trace_rcu_utilization("Start scheduler-tick"); |
a858af28 | 1719 | increment_cpu_stall_ticks(); |
9b2e4f18 | 1720 | if (user || rcu_is_cpu_rrupt_from_idle()) { |
64db4cff PM |
1721 | |
1722 | /* | |
1723 | * Get here if this CPU took its interrupt from user | |
1724 | * mode or from the idle loop, and if this is not a | |
1725 | * nested interrupt. In this case, the CPU is in | |
d6714c22 | 1726 | * a quiescent state, so note it. |
64db4cff PM |
1727 | * |
1728 | * No memory barrier is required here because both | |
d6714c22 PM |
1729 | * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
1730 | * variables that other CPUs neither access nor modify, | |
1731 | * at least not while the corresponding CPU is online. | |
64db4cff PM |
1732 | */ |
1733 | ||
d6714c22 PM |
1734 | rcu_sched_qs(cpu); |
1735 | rcu_bh_qs(cpu); | |
64db4cff PM |
1736 | |
1737 | } else if (!in_softirq()) { | |
1738 | ||
1739 | /* | |
1740 | * Get here if this CPU did not take its interrupt from | |
1741 | * softirq, in other words, if it is not interrupting | |
1742 | * a rcu_bh read-side critical section. This is an _bh | |
d6714c22 | 1743 | * critical section, so note it. |
64db4cff PM |
1744 | */ |
1745 | ||
d6714c22 | 1746 | rcu_bh_qs(cpu); |
64db4cff | 1747 | } |
f41d911f | 1748 | rcu_preempt_check_callbacks(cpu); |
d21670ac | 1749 | if (rcu_pending(cpu)) |
a46e0899 | 1750 | invoke_rcu_core(); |
300df91c | 1751 | trace_rcu_utilization("End scheduler-tick"); |
64db4cff PM |
1752 | } |
1753 | ||
64db4cff PM |
1754 | /* |
1755 | * Scan the leaf rcu_node structures, processing dyntick state for any that | |
1756 | * have not yet encountered a quiescent state, using the function specified. | |
27f4d280 PM |
1757 | * Also initiate boosting for any threads blocked on the root rcu_node. |
1758 | * | |
ee47eb9f | 1759 | * The caller must have suppressed start of new grace periods. |
64db4cff | 1760 | */ |
45f014c5 | 1761 | static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)) |
64db4cff PM |
1762 | { |
1763 | unsigned long bit; | |
1764 | int cpu; | |
1765 | unsigned long flags; | |
1766 | unsigned long mask; | |
a0b6c9a7 | 1767 | struct rcu_node *rnp; |
64db4cff | 1768 | |
a0b6c9a7 | 1769 | rcu_for_each_leaf_node(rsp, rnp) { |
64db4cff | 1770 | mask = 0; |
1304afb2 | 1771 | raw_spin_lock_irqsave(&rnp->lock, flags); |
ee47eb9f | 1772 | if (!rcu_gp_in_progress(rsp)) { |
1304afb2 | 1773 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
0f10dc82 | 1774 | return; |
64db4cff | 1775 | } |
a0b6c9a7 | 1776 | if (rnp->qsmask == 0) { |
1217ed1b | 1777 | rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ |
64db4cff PM |
1778 | continue; |
1779 | } | |
a0b6c9a7 | 1780 | cpu = rnp->grplo; |
64db4cff | 1781 | bit = 1; |
a0b6c9a7 | 1782 | for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { |
394f99a9 LJ |
1783 | if ((rnp->qsmask & bit) != 0 && |
1784 | f(per_cpu_ptr(rsp->rda, cpu))) | |
64db4cff PM |
1785 | mask |= bit; |
1786 | } | |
45f014c5 | 1787 | if (mask != 0) { |
64db4cff | 1788 | |
d3f6bad3 PM |
1789 | /* rcu_report_qs_rnp() releases rnp->lock. */ |
1790 | rcu_report_qs_rnp(mask, rsp, rnp, flags); | |
64db4cff PM |
1791 | continue; |
1792 | } | |
1304afb2 | 1793 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
64db4cff | 1794 | } |
27f4d280 | 1795 | rnp = rcu_get_root(rsp); |
1217ed1b PM |
1796 | if (rnp->qsmask == 0) { |
1797 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
1798 | rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */ | |
1799 | } | |
64db4cff PM |
1800 | } |
1801 | ||
1802 | /* | |
1803 | * Force quiescent states on reluctant CPUs, and also detect which | |
1804 | * CPUs are in dyntick-idle mode. | |
1805 | */ | |
4cdfc175 | 1806 | static void force_quiescent_state(struct rcu_state *rsp) |
64db4cff PM |
1807 | { |
1808 | unsigned long flags; | |
64db4cff | 1809 | struct rcu_node *rnp = rcu_get_root(rsp); |
64db4cff | 1810 | |
4cdfc175 PM |
1811 | if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) |
1812 | return; /* Someone beat us to it. */ | |
1813 | if (!raw_spin_trylock_irqsave(&rnp->lock, flags)) { | |
64db4cff | 1814 | rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */ |
46a1e34e PM |
1815 | return; |
1816 | } | |
4cdfc175 PM |
1817 | rsp->gp_flags |= RCU_GP_FLAG_FQS; |
1818 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
1819 | wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */ | |
64db4cff PM |
1820 | } |
1821 | ||
64db4cff | 1822 | /* |
e0f23060 PM |
1823 | * This does the RCU core processing work for the specified rcu_state |
1824 | * and rcu_data structures. This may be called only from the CPU to | |
1825 | * whom the rdp belongs. | |
64db4cff PM |
1826 | */ |
1827 | static void | |
1bca8cf1 | 1828 | __rcu_process_callbacks(struct rcu_state *rsp) |
64db4cff PM |
1829 | { |
1830 | unsigned long flags; | |
1bca8cf1 | 1831 | struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); |
64db4cff | 1832 | |
2e597558 PM |
1833 | WARN_ON_ONCE(rdp->beenonline == 0); |
1834 | ||
64db4cff PM |
1835 | /* |
1836 | * Advance callbacks in response to end of earlier grace | |
1837 | * period that some other CPU ended. | |
1838 | */ | |
1839 | rcu_process_gp_end(rsp, rdp); | |
1840 | ||
1841 | /* Update RCU state based on any recent quiescent states. */ | |
1842 | rcu_check_quiescent_state(rsp, rdp); | |
1843 | ||
1844 | /* Does this CPU require a not-yet-started grace period? */ | |
1845 | if (cpu_needs_another_gp(rsp, rdp)) { | |
1304afb2 | 1846 | raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags); |
64db4cff PM |
1847 | rcu_start_gp(rsp, flags); /* releases above lock */ |
1848 | } | |
1849 | ||
1850 | /* If there are callbacks ready, invoke them. */ | |
09223371 | 1851 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
a46e0899 | 1852 | invoke_rcu_callbacks(rsp, rdp); |
09223371 SL |
1853 | } |
1854 | ||
64db4cff | 1855 | /* |
e0f23060 | 1856 | * Do RCU core processing for the current CPU. |
64db4cff | 1857 | */ |
09223371 | 1858 | static void rcu_process_callbacks(struct softirq_action *unused) |
64db4cff | 1859 | { |
6ce75a23 PM |
1860 | struct rcu_state *rsp; |
1861 | ||
bfa00b4c PM |
1862 | if (cpu_is_offline(smp_processor_id())) |
1863 | return; | |
300df91c | 1864 | trace_rcu_utilization("Start RCU core"); |
6ce75a23 PM |
1865 | for_each_rcu_flavor(rsp) |
1866 | __rcu_process_callbacks(rsp); | |
300df91c | 1867 | trace_rcu_utilization("End RCU core"); |
64db4cff PM |
1868 | } |
1869 | ||
a26ac245 | 1870 | /* |
e0f23060 PM |
1871 | * Schedule RCU callback invocation. If the specified type of RCU |
1872 | * does not support RCU priority boosting, just do a direct call, | |
1873 | * otherwise wake up the per-CPU kernel kthread. Note that because we | |
1874 | * are running on the current CPU with interrupts disabled, the | |
1875 | * rcu_cpu_kthread_task cannot disappear out from under us. | |
a26ac245 | 1876 | */ |
a46e0899 | 1877 | static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) |
a26ac245 | 1878 | { |
b0d30417 PM |
1879 | if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active))) |
1880 | return; | |
a46e0899 PM |
1881 | if (likely(!rsp->boost)) { |
1882 | rcu_do_batch(rsp, rdp); | |
a26ac245 PM |
1883 | return; |
1884 | } | |
a46e0899 | 1885 | invoke_rcu_callbacks_kthread(); |
a26ac245 PM |
1886 | } |
1887 | ||
a46e0899 | 1888 | static void invoke_rcu_core(void) |
09223371 SL |
1889 | { |
1890 | raise_softirq(RCU_SOFTIRQ); | |
1891 | } | |
1892 | ||
29154c57 PM |
1893 | /* |
1894 | * Handle any core-RCU processing required by a call_rcu() invocation. | |
1895 | */ | |
1896 | static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp, | |
1897 | struct rcu_head *head, unsigned long flags) | |
64db4cff | 1898 | { |
62fde6ed PM |
1899 | /* |
1900 | * If called from an extended quiescent state, invoke the RCU | |
1901 | * core in order to force a re-evaluation of RCU's idleness. | |
1902 | */ | |
a16b7a69 | 1903 | if (rcu_is_cpu_idle() && cpu_online(smp_processor_id())) |
62fde6ed PM |
1904 | invoke_rcu_core(); |
1905 | ||
a16b7a69 | 1906 | /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ |
29154c57 | 1907 | if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) |
2655d57e | 1908 | return; |
64db4cff | 1909 | |
37c72e56 PM |
1910 | /* |
1911 | * Force the grace period if too many callbacks or too long waiting. | |
1912 | * Enforce hysteresis, and don't invoke force_quiescent_state() | |
1913 | * if some other CPU has recently done so. Also, don't bother | |
1914 | * invoking force_quiescent_state() if the newly enqueued callback | |
1915 | * is the only one waiting for a grace period to complete. | |
1916 | */ | |
2655d57e | 1917 | if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { |
b52573d2 PM |
1918 | |
1919 | /* Are we ignoring a completed grace period? */ | |
1920 | rcu_process_gp_end(rsp, rdp); | |
1921 | check_for_new_grace_period(rsp, rdp); | |
1922 | ||
1923 | /* Start a new grace period if one not already started. */ | |
1924 | if (!rcu_gp_in_progress(rsp)) { | |
1925 | unsigned long nestflag; | |
1926 | struct rcu_node *rnp_root = rcu_get_root(rsp); | |
1927 | ||
1928 | raw_spin_lock_irqsave(&rnp_root->lock, nestflag); | |
1929 | rcu_start_gp(rsp, nestflag); /* rlses rnp_root->lock */ | |
1930 | } else { | |
1931 | /* Give the grace period a kick. */ | |
1932 | rdp->blimit = LONG_MAX; | |
1933 | if (rsp->n_force_qs == rdp->n_force_qs_snap && | |
1934 | *rdp->nxttail[RCU_DONE_TAIL] != head) | |
4cdfc175 | 1935 | force_quiescent_state(rsp); |
b52573d2 PM |
1936 | rdp->n_force_qs_snap = rsp->n_force_qs; |
1937 | rdp->qlen_last_fqs_check = rdp->qlen; | |
1938 | } | |
4cdfc175 | 1939 | } |
29154c57 PM |
1940 | } |
1941 | ||
64db4cff PM |
1942 | static void |
1943 | __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), | |
486e2593 | 1944 | struct rcu_state *rsp, bool lazy) |
64db4cff PM |
1945 | { |
1946 | unsigned long flags; | |
1947 | struct rcu_data *rdp; | |
1948 | ||
0bb7b59d | 1949 | WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */ |
551d55a9 | 1950 | debug_rcu_head_queue(head); |
64db4cff PM |
1951 | head->func = func; |
1952 | head->next = NULL; | |
1953 | ||
1954 | smp_mb(); /* Ensure RCU update seen before callback registry. */ | |
1955 | ||
1956 | /* | |
1957 | * Opportunistically note grace-period endings and beginnings. | |
1958 | * Note that we might see a beginning right after we see an | |
1959 | * end, but never vice versa, since this CPU has to pass through | |
1960 | * a quiescent state betweentimes. | |
1961 | */ | |
1962 | local_irq_save(flags); | |
394f99a9 | 1963 | rdp = this_cpu_ptr(rsp->rda); |
64db4cff PM |
1964 | |
1965 | /* Add the callback to our list. */ | |
29154c57 | 1966 | ACCESS_ONCE(rdp->qlen)++; |
486e2593 PM |
1967 | if (lazy) |
1968 | rdp->qlen_lazy++; | |
c57afe80 PM |
1969 | else |
1970 | rcu_idle_count_callbacks_posted(); | |
b1420f1c PM |
1971 | smp_mb(); /* Count before adding callback for rcu_barrier(). */ |
1972 | *rdp->nxttail[RCU_NEXT_TAIL] = head; | |
1973 | rdp->nxttail[RCU_NEXT_TAIL] = &head->next; | |
2655d57e | 1974 | |
d4c08f2a PM |
1975 | if (__is_kfree_rcu_offset((unsigned long)func)) |
1976 | trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func, | |
486e2593 | 1977 | rdp->qlen_lazy, rdp->qlen); |
d4c08f2a | 1978 | else |
486e2593 | 1979 | trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen); |
d4c08f2a | 1980 | |
29154c57 PM |
1981 | /* Go handle any RCU core processing required. */ |
1982 | __call_rcu_core(rsp, rdp, head, flags); | |
64db4cff PM |
1983 | local_irq_restore(flags); |
1984 | } | |
1985 | ||
1986 | /* | |
d6714c22 | 1987 | * Queue an RCU-sched callback for invocation after a grace period. |
64db4cff | 1988 | */ |
d6714c22 | 1989 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
64db4cff | 1990 | { |
486e2593 | 1991 | __call_rcu(head, func, &rcu_sched_state, 0); |
64db4cff | 1992 | } |
d6714c22 | 1993 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
64db4cff PM |
1994 | |
1995 | /* | |
486e2593 | 1996 | * Queue an RCU callback for invocation after a quicker grace period. |
64db4cff PM |
1997 | */ |
1998 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
1999 | { | |
486e2593 | 2000 | __call_rcu(head, func, &rcu_bh_state, 0); |
64db4cff PM |
2001 | } |
2002 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
2003 | ||
6d813391 PM |
2004 | /* |
2005 | * Because a context switch is a grace period for RCU-sched and RCU-bh, | |
2006 | * any blocking grace-period wait automatically implies a grace period | |
2007 | * if there is only one CPU online at any point time during execution | |
2008 | * of either synchronize_sched() or synchronize_rcu_bh(). It is OK to | |
2009 | * occasionally incorrectly indicate that there are multiple CPUs online | |
2010 | * when there was in fact only one the whole time, as this just adds | |
2011 | * some overhead: RCU still operates correctly. | |
6d813391 PM |
2012 | */ |
2013 | static inline int rcu_blocking_is_gp(void) | |
2014 | { | |
95f0c1de PM |
2015 | int ret; |
2016 | ||
6d813391 | 2017 | might_sleep(); /* Check for RCU read-side critical section. */ |
95f0c1de PM |
2018 | preempt_disable(); |
2019 | ret = num_online_cpus() <= 1; | |
2020 | preempt_enable(); | |
2021 | return ret; | |
6d813391 PM |
2022 | } |
2023 | ||
6ebb237b PM |
2024 | /** |
2025 | * synchronize_sched - wait until an rcu-sched grace period has elapsed. | |
2026 | * | |
2027 | * Control will return to the caller some time after a full rcu-sched | |
2028 | * grace period has elapsed, in other words after all currently executing | |
2029 | * rcu-sched read-side critical sections have completed. These read-side | |
2030 | * critical sections are delimited by rcu_read_lock_sched() and | |
2031 | * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), | |
2032 | * local_irq_disable(), and so on may be used in place of | |
2033 | * rcu_read_lock_sched(). | |
2034 | * | |
2035 | * This means that all preempt_disable code sequences, including NMI and | |
2036 | * hardware-interrupt handlers, in progress on entry will have completed | |
2037 | * before this primitive returns. However, this does not guarantee that | |
2038 | * softirq handlers will have completed, since in some kernels, these | |
2039 | * handlers can run in process context, and can block. | |
2040 | * | |
2041 | * This primitive provides the guarantees made by the (now removed) | |
2042 | * synchronize_kernel() API. In contrast, synchronize_rcu() only | |
2043 | * guarantees that rcu_read_lock() sections will have completed. | |
2044 | * In "classic RCU", these two guarantees happen to be one and | |
2045 | * the same, but can differ in realtime RCU implementations. | |
2046 | */ | |
2047 | void synchronize_sched(void) | |
2048 | { | |
fe15d706 PM |
2049 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
2050 | !lock_is_held(&rcu_lock_map) && | |
2051 | !lock_is_held(&rcu_sched_lock_map), | |
2052 | "Illegal synchronize_sched() in RCU-sched read-side critical section"); | |
6ebb237b PM |
2053 | if (rcu_blocking_is_gp()) |
2054 | return; | |
2c42818e | 2055 | wait_rcu_gp(call_rcu_sched); |
6ebb237b PM |
2056 | } |
2057 | EXPORT_SYMBOL_GPL(synchronize_sched); | |
2058 | ||
2059 | /** | |
2060 | * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. | |
2061 | * | |
2062 | * Control will return to the caller some time after a full rcu_bh grace | |
2063 | * period has elapsed, in other words after all currently executing rcu_bh | |
2064 | * read-side critical sections have completed. RCU read-side critical | |
2065 | * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), | |
2066 | * and may be nested. | |
2067 | */ | |
2068 | void synchronize_rcu_bh(void) | |
2069 | { | |
fe15d706 PM |
2070 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
2071 | !lock_is_held(&rcu_lock_map) && | |
2072 | !lock_is_held(&rcu_sched_lock_map), | |
2073 | "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section"); | |
6ebb237b PM |
2074 | if (rcu_blocking_is_gp()) |
2075 | return; | |
2c42818e | 2076 | wait_rcu_gp(call_rcu_bh); |
6ebb237b PM |
2077 | } |
2078 | EXPORT_SYMBOL_GPL(synchronize_rcu_bh); | |
2079 | ||
3d3b7db0 PM |
2080 | static atomic_t sync_sched_expedited_started = ATOMIC_INIT(0); |
2081 | static atomic_t sync_sched_expedited_done = ATOMIC_INIT(0); | |
2082 | ||
2083 | static int synchronize_sched_expedited_cpu_stop(void *data) | |
2084 | { | |
2085 | /* | |
2086 | * There must be a full memory barrier on each affected CPU | |
2087 | * between the time that try_stop_cpus() is called and the | |
2088 | * time that it returns. | |
2089 | * | |
2090 | * In the current initial implementation of cpu_stop, the | |
2091 | * above condition is already met when the control reaches | |
2092 | * this point and the following smp_mb() is not strictly | |
2093 | * necessary. Do smp_mb() anyway for documentation and | |
2094 | * robustness against future implementation changes. | |
2095 | */ | |
2096 | smp_mb(); /* See above comment block. */ | |
2097 | return 0; | |
2098 | } | |
2099 | ||
236fefaf PM |
2100 | /** |
2101 | * synchronize_sched_expedited - Brute-force RCU-sched grace period | |
2102 | * | |
2103 | * Wait for an RCU-sched grace period to elapse, but use a "big hammer" | |
2104 | * approach to force the grace period to end quickly. This consumes | |
2105 | * significant time on all CPUs and is unfriendly to real-time workloads, | |
2106 | * so is thus not recommended for any sort of common-case code. In fact, | |
2107 | * if you are using synchronize_sched_expedited() in a loop, please | |
2108 | * restructure your code to batch your updates, and then use a single | |
2109 | * synchronize_sched() instead. | |
3d3b7db0 | 2110 | * |
236fefaf PM |
2111 | * Note that it is illegal to call this function while holding any lock |
2112 | * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal | |
2113 | * to call this function from a CPU-hotplug notifier. Failing to observe | |
2114 | * these restriction will result in deadlock. | |
3d3b7db0 PM |
2115 | * |
2116 | * This implementation can be thought of as an application of ticket | |
2117 | * locking to RCU, with sync_sched_expedited_started and | |
2118 | * sync_sched_expedited_done taking on the roles of the halves | |
2119 | * of the ticket-lock word. Each task atomically increments | |
2120 | * sync_sched_expedited_started upon entry, snapshotting the old value, | |
2121 | * then attempts to stop all the CPUs. If this succeeds, then each | |
2122 | * CPU will have executed a context switch, resulting in an RCU-sched | |
2123 | * grace period. We are then done, so we use atomic_cmpxchg() to | |
2124 | * update sync_sched_expedited_done to match our snapshot -- but | |
2125 | * only if someone else has not already advanced past our snapshot. | |
2126 | * | |
2127 | * On the other hand, if try_stop_cpus() fails, we check the value | |
2128 | * of sync_sched_expedited_done. If it has advanced past our | |
2129 | * initial snapshot, then someone else must have forced a grace period | |
2130 | * some time after we took our snapshot. In this case, our work is | |
2131 | * done for us, and we can simply return. Otherwise, we try again, | |
2132 | * but keep our initial snapshot for purposes of checking for someone | |
2133 | * doing our work for us. | |
2134 | * | |
2135 | * If we fail too many times in a row, we fall back to synchronize_sched(). | |
2136 | */ | |
2137 | void synchronize_sched_expedited(void) | |
2138 | { | |
2139 | int firstsnap, s, snap, trycount = 0; | |
2140 | ||
2141 | /* Note that atomic_inc_return() implies full memory barrier. */ | |
2142 | firstsnap = snap = atomic_inc_return(&sync_sched_expedited_started); | |
2143 | get_online_cpus(); | |
1cc85961 | 2144 | WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id())); |
3d3b7db0 PM |
2145 | |
2146 | /* | |
2147 | * Each pass through the following loop attempts to force a | |
2148 | * context switch on each CPU. | |
2149 | */ | |
2150 | while (try_stop_cpus(cpu_online_mask, | |
2151 | synchronize_sched_expedited_cpu_stop, | |
2152 | NULL) == -EAGAIN) { | |
2153 | put_online_cpus(); | |
2154 | ||
2155 | /* No joy, try again later. Or just synchronize_sched(). */ | |
c701d5d9 | 2156 | if (trycount++ < 10) { |
3d3b7db0 | 2157 | udelay(trycount * num_online_cpus()); |
c701d5d9 | 2158 | } else { |
3d3b7db0 PM |
2159 | synchronize_sched(); |
2160 | return; | |
2161 | } | |
2162 | ||
2163 | /* Check to see if someone else did our work for us. */ | |
2164 | s = atomic_read(&sync_sched_expedited_done); | |
2165 | if (UINT_CMP_GE((unsigned)s, (unsigned)firstsnap)) { | |
2166 | smp_mb(); /* ensure test happens before caller kfree */ | |
2167 | return; | |
2168 | } | |
2169 | ||
2170 | /* | |
2171 | * Refetching sync_sched_expedited_started allows later | |
2172 | * callers to piggyback on our grace period. We subtract | |
2173 | * 1 to get the same token that the last incrementer got. | |
2174 | * We retry after they started, so our grace period works | |
2175 | * for them, and they started after our first try, so their | |
2176 | * grace period works for us. | |
2177 | */ | |
2178 | get_online_cpus(); | |
2179 | snap = atomic_read(&sync_sched_expedited_started); | |
2180 | smp_mb(); /* ensure read is before try_stop_cpus(). */ | |
2181 | } | |
2182 | ||
2183 | /* | |
2184 | * Everyone up to our most recent fetch is covered by our grace | |
2185 | * period. Update the counter, but only if our work is still | |
2186 | * relevant -- which it won't be if someone who started later | |
2187 | * than we did beat us to the punch. | |
2188 | */ | |
2189 | do { | |
2190 | s = atomic_read(&sync_sched_expedited_done); | |
2191 | if (UINT_CMP_GE((unsigned)s, (unsigned)snap)) { | |
2192 | smp_mb(); /* ensure test happens before caller kfree */ | |
2193 | break; | |
2194 | } | |
2195 | } while (atomic_cmpxchg(&sync_sched_expedited_done, s, snap) != s); | |
2196 | ||
2197 | put_online_cpus(); | |
2198 | } | |
2199 | EXPORT_SYMBOL_GPL(synchronize_sched_expedited); | |
2200 | ||
64db4cff PM |
2201 | /* |
2202 | * Check to see if there is any immediate RCU-related work to be done | |
2203 | * by the current CPU, for the specified type of RCU, returning 1 if so. | |
2204 | * The checks are in order of increasing expense: checks that can be | |
2205 | * carried out against CPU-local state are performed first. However, | |
2206 | * we must check for CPU stalls first, else we might not get a chance. | |
2207 | */ | |
2208 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) | |
2209 | { | |
2f51f988 PM |
2210 | struct rcu_node *rnp = rdp->mynode; |
2211 | ||
64db4cff PM |
2212 | rdp->n_rcu_pending++; |
2213 | ||
2214 | /* Check for CPU stalls, if enabled. */ | |
2215 | check_cpu_stall(rsp, rdp); | |
2216 | ||
2217 | /* Is the RCU core waiting for a quiescent state from this CPU? */ | |
5c51dd73 PM |
2218 | if (rcu_scheduler_fully_active && |
2219 | rdp->qs_pending && !rdp->passed_quiesce) { | |
d21670ac | 2220 | rdp->n_rp_qs_pending++; |
e4cc1f22 | 2221 | } else if (rdp->qs_pending && rdp->passed_quiesce) { |
d21670ac | 2222 | rdp->n_rp_report_qs++; |
64db4cff | 2223 | return 1; |
7ba5c840 | 2224 | } |
64db4cff PM |
2225 | |
2226 | /* Does this CPU have callbacks ready to invoke? */ | |
7ba5c840 PM |
2227 | if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
2228 | rdp->n_rp_cb_ready++; | |
64db4cff | 2229 | return 1; |
7ba5c840 | 2230 | } |
64db4cff PM |
2231 | |
2232 | /* Has RCU gone idle with this CPU needing another grace period? */ | |
7ba5c840 PM |
2233 | if (cpu_needs_another_gp(rsp, rdp)) { |
2234 | rdp->n_rp_cpu_needs_gp++; | |
64db4cff | 2235 | return 1; |
7ba5c840 | 2236 | } |
64db4cff PM |
2237 | |
2238 | /* Has another RCU grace period completed? */ | |
2f51f988 | 2239 | if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ |
7ba5c840 | 2240 | rdp->n_rp_gp_completed++; |
64db4cff | 2241 | return 1; |
7ba5c840 | 2242 | } |
64db4cff PM |
2243 | |
2244 | /* Has a new RCU grace period started? */ | |
2f51f988 | 2245 | if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */ |
7ba5c840 | 2246 | rdp->n_rp_gp_started++; |
64db4cff | 2247 | return 1; |
7ba5c840 | 2248 | } |
64db4cff | 2249 | |
64db4cff | 2250 | /* nothing to do */ |
7ba5c840 | 2251 | rdp->n_rp_need_nothing++; |
64db4cff PM |
2252 | return 0; |
2253 | } | |
2254 | ||
2255 | /* | |
2256 | * Check to see if there is any immediate RCU-related work to be done | |
2257 | * by the current CPU, returning 1 if so. This function is part of the | |
2258 | * RCU implementation; it is -not- an exported member of the RCU API. | |
2259 | */ | |
a157229c | 2260 | static int rcu_pending(int cpu) |
64db4cff | 2261 | { |
6ce75a23 PM |
2262 | struct rcu_state *rsp; |
2263 | ||
2264 | for_each_rcu_flavor(rsp) | |
2265 | if (__rcu_pending(rsp, per_cpu_ptr(rsp->rda, cpu))) | |
2266 | return 1; | |
2267 | return 0; | |
64db4cff PM |
2268 | } |
2269 | ||
2270 | /* | |
2271 | * Check to see if any future RCU-related work will need to be done | |
2272 | * by the current CPU, even if none need be done immediately, returning | |
8bd93a2c | 2273 | * 1 if so. |
64db4cff | 2274 | */ |
aea1b35e | 2275 | static int rcu_cpu_has_callbacks(int cpu) |
64db4cff | 2276 | { |
6ce75a23 PM |
2277 | struct rcu_state *rsp; |
2278 | ||
64db4cff | 2279 | /* RCU callbacks either ready or pending? */ |
6ce75a23 PM |
2280 | for_each_rcu_flavor(rsp) |
2281 | if (per_cpu_ptr(rsp->rda, cpu)->nxtlist) | |
2282 | return 1; | |
2283 | return 0; | |
64db4cff PM |
2284 | } |
2285 | ||
a83eff0a PM |
2286 | /* |
2287 | * Helper function for _rcu_barrier() tracing. If tracing is disabled, | |
2288 | * the compiler is expected to optimize this away. | |
2289 | */ | |
2290 | static void _rcu_barrier_trace(struct rcu_state *rsp, char *s, | |
2291 | int cpu, unsigned long done) | |
2292 | { | |
2293 | trace_rcu_barrier(rsp->name, s, cpu, | |
2294 | atomic_read(&rsp->barrier_cpu_count), done); | |
2295 | } | |
2296 | ||
b1420f1c PM |
2297 | /* |
2298 | * RCU callback function for _rcu_barrier(). If we are last, wake | |
2299 | * up the task executing _rcu_barrier(). | |
2300 | */ | |
24ebbca8 | 2301 | static void rcu_barrier_callback(struct rcu_head *rhp) |
d0ec774c | 2302 | { |
24ebbca8 PM |
2303 | struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head); |
2304 | struct rcu_state *rsp = rdp->rsp; | |
2305 | ||
a83eff0a PM |
2306 | if (atomic_dec_and_test(&rsp->barrier_cpu_count)) { |
2307 | _rcu_barrier_trace(rsp, "LastCB", -1, rsp->n_barrier_done); | |
7db74df8 | 2308 | complete(&rsp->barrier_completion); |
a83eff0a PM |
2309 | } else { |
2310 | _rcu_barrier_trace(rsp, "CB", -1, rsp->n_barrier_done); | |
2311 | } | |
d0ec774c PM |
2312 | } |
2313 | ||
2314 | /* | |
2315 | * Called with preemption disabled, and from cross-cpu IRQ context. | |
2316 | */ | |
2317 | static void rcu_barrier_func(void *type) | |
2318 | { | |
037b64ed | 2319 | struct rcu_state *rsp = type; |
06668efa | 2320 | struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); |
d0ec774c | 2321 | |
a83eff0a | 2322 | _rcu_barrier_trace(rsp, "IRQ", -1, rsp->n_barrier_done); |
24ebbca8 | 2323 | atomic_inc(&rsp->barrier_cpu_count); |
06668efa | 2324 | rsp->call(&rdp->barrier_head, rcu_barrier_callback); |
d0ec774c PM |
2325 | } |
2326 | ||
d0ec774c PM |
2327 | /* |
2328 | * Orchestrate the specified type of RCU barrier, waiting for all | |
2329 | * RCU callbacks of the specified type to complete. | |
2330 | */ | |
037b64ed | 2331 | static void _rcu_barrier(struct rcu_state *rsp) |
d0ec774c | 2332 | { |
b1420f1c PM |
2333 | int cpu; |
2334 | unsigned long flags; | |
2335 | struct rcu_data *rdp; | |
24ebbca8 | 2336 | struct rcu_data rd; |
cf3a9c48 PM |
2337 | unsigned long snap = ACCESS_ONCE(rsp->n_barrier_done); |
2338 | unsigned long snap_done; | |
b1420f1c | 2339 | |
24ebbca8 | 2340 | init_rcu_head_on_stack(&rd.barrier_head); |
a83eff0a | 2341 | _rcu_barrier_trace(rsp, "Begin", -1, snap); |
b1420f1c | 2342 | |
e74f4c45 | 2343 | /* Take mutex to serialize concurrent rcu_barrier() requests. */ |
7be7f0be | 2344 | mutex_lock(&rsp->barrier_mutex); |
b1420f1c | 2345 | |
cf3a9c48 PM |
2346 | /* |
2347 | * Ensure that all prior references, including to ->n_barrier_done, | |
2348 | * are ordered before the _rcu_barrier() machinery. | |
2349 | */ | |
2350 | smp_mb(); /* See above block comment. */ | |
2351 | ||
2352 | /* | |
2353 | * Recheck ->n_barrier_done to see if others did our work for us. | |
2354 | * This means checking ->n_barrier_done for an even-to-odd-to-even | |
2355 | * transition. The "if" expression below therefore rounds the old | |
2356 | * value up to the next even number and adds two before comparing. | |
2357 | */ | |
2358 | snap_done = ACCESS_ONCE(rsp->n_barrier_done); | |
a83eff0a | 2359 | _rcu_barrier_trace(rsp, "Check", -1, snap_done); |
cf3a9c48 | 2360 | if (ULONG_CMP_GE(snap_done, ((snap + 1) & ~0x1) + 2)) { |
a83eff0a | 2361 | _rcu_barrier_trace(rsp, "EarlyExit", -1, snap_done); |
cf3a9c48 PM |
2362 | smp_mb(); /* caller's subsequent code after above check. */ |
2363 | mutex_unlock(&rsp->barrier_mutex); | |
2364 | return; | |
2365 | } | |
2366 | ||
2367 | /* | |
2368 | * Increment ->n_barrier_done to avoid duplicate work. Use | |
2369 | * ACCESS_ONCE() to prevent the compiler from speculating | |
2370 | * the increment to precede the early-exit check. | |
2371 | */ | |
2372 | ACCESS_ONCE(rsp->n_barrier_done)++; | |
2373 | WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 1); | |
a83eff0a | 2374 | _rcu_barrier_trace(rsp, "Inc1", -1, rsp->n_barrier_done); |
cf3a9c48 | 2375 | smp_mb(); /* Order ->n_barrier_done increment with below mechanism. */ |
b1420f1c | 2376 | |
d0ec774c | 2377 | /* |
b1420f1c PM |
2378 | * Initialize the count to one rather than to zero in order to |
2379 | * avoid a too-soon return to zero in case of a short grace period | |
2380 | * (or preemption of this task). Also flag this task as doing | |
2381 | * an rcu_barrier(). This will prevent anyone else from adopting | |
2382 | * orphaned callbacks, which could cause otherwise failure if a | |
2383 | * CPU went offline and quickly came back online. To see this, | |
2384 | * consider the following sequence of events: | |
2385 | * | |
2386 | * 1. We cause CPU 0 to post an rcu_barrier_callback() callback. | |
2387 | * 2. CPU 1 goes offline, orphaning its callbacks. | |
2388 | * 3. CPU 0 adopts CPU 1's orphaned callbacks. | |
2389 | * 4. CPU 1 comes back online. | |
2390 | * 5. We cause CPU 1 to post an rcu_barrier_callback() callback. | |
2391 | * 6. Both rcu_barrier_callback() callbacks are invoked, awakening | |
2392 | * us -- but before CPU 1's orphaned callbacks are invoked!!! | |
d0ec774c | 2393 | */ |
7db74df8 | 2394 | init_completion(&rsp->barrier_completion); |
24ebbca8 | 2395 | atomic_set(&rsp->barrier_cpu_count, 1); |
b1420f1c PM |
2396 | raw_spin_lock_irqsave(&rsp->onofflock, flags); |
2397 | rsp->rcu_barrier_in_progress = current; | |
2398 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); | |
2399 | ||
2400 | /* | |
2401 | * Force every CPU with callbacks to register a new callback | |
2402 | * that will tell us when all the preceding callbacks have | |
2403 | * been invoked. If an offline CPU has callbacks, wait for | |
2404 | * it to either come back online or to finish orphaning those | |
2405 | * callbacks. | |
2406 | */ | |
2407 | for_each_possible_cpu(cpu) { | |
2408 | preempt_disable(); | |
2409 | rdp = per_cpu_ptr(rsp->rda, cpu); | |
2410 | if (cpu_is_offline(cpu)) { | |
a83eff0a PM |
2411 | _rcu_barrier_trace(rsp, "Offline", cpu, |
2412 | rsp->n_barrier_done); | |
b1420f1c PM |
2413 | preempt_enable(); |
2414 | while (cpu_is_offline(cpu) && ACCESS_ONCE(rdp->qlen)) | |
2415 | schedule_timeout_interruptible(1); | |
2416 | } else if (ACCESS_ONCE(rdp->qlen)) { | |
a83eff0a PM |
2417 | _rcu_barrier_trace(rsp, "OnlineQ", cpu, |
2418 | rsp->n_barrier_done); | |
037b64ed | 2419 | smp_call_function_single(cpu, rcu_barrier_func, rsp, 1); |
b1420f1c PM |
2420 | preempt_enable(); |
2421 | } else { | |
a83eff0a PM |
2422 | _rcu_barrier_trace(rsp, "OnlineNQ", cpu, |
2423 | rsp->n_barrier_done); | |
b1420f1c PM |
2424 | preempt_enable(); |
2425 | } | |
2426 | } | |
2427 | ||
2428 | /* | |
2429 | * Now that all online CPUs have rcu_barrier_callback() callbacks | |
2430 | * posted, we can adopt all of the orphaned callbacks and place | |
2431 | * an rcu_barrier_callback() callback after them. When that is done, | |
2432 | * we are guaranteed to have an rcu_barrier_callback() callback | |
2433 | * following every callback that could possibly have been | |
2434 | * registered before _rcu_barrier() was called. | |
2435 | */ | |
2436 | raw_spin_lock_irqsave(&rsp->onofflock, flags); | |
2437 | rcu_adopt_orphan_cbs(rsp); | |
2438 | rsp->rcu_barrier_in_progress = NULL; | |
2439 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); | |
24ebbca8 | 2440 | atomic_inc(&rsp->barrier_cpu_count); |
b1420f1c | 2441 | smp_mb__after_atomic_inc(); /* Ensure atomic_inc() before callback. */ |
24ebbca8 PM |
2442 | rd.rsp = rsp; |
2443 | rsp->call(&rd.barrier_head, rcu_barrier_callback); | |
b1420f1c PM |
2444 | |
2445 | /* | |
2446 | * Now that we have an rcu_barrier_callback() callback on each | |
2447 | * CPU, and thus each counted, remove the initial count. | |
2448 | */ | |
24ebbca8 | 2449 | if (atomic_dec_and_test(&rsp->barrier_cpu_count)) |
7db74df8 | 2450 | complete(&rsp->barrier_completion); |
b1420f1c | 2451 | |
cf3a9c48 PM |
2452 | /* Increment ->n_barrier_done to prevent duplicate work. */ |
2453 | smp_mb(); /* Keep increment after above mechanism. */ | |
2454 | ACCESS_ONCE(rsp->n_barrier_done)++; | |
2455 | WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 0); | |
a83eff0a | 2456 | _rcu_barrier_trace(rsp, "Inc2", -1, rsp->n_barrier_done); |
cf3a9c48 PM |
2457 | smp_mb(); /* Keep increment before caller's subsequent code. */ |
2458 | ||
b1420f1c | 2459 | /* Wait for all rcu_barrier_callback() callbacks to be invoked. */ |
7db74df8 | 2460 | wait_for_completion(&rsp->barrier_completion); |
b1420f1c PM |
2461 | |
2462 | /* Other rcu_barrier() invocations can now safely proceed. */ | |
7be7f0be | 2463 | mutex_unlock(&rsp->barrier_mutex); |
b1420f1c | 2464 | |
24ebbca8 | 2465 | destroy_rcu_head_on_stack(&rd.barrier_head); |
d0ec774c | 2466 | } |
d0ec774c PM |
2467 | |
2468 | /** | |
2469 | * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. | |
2470 | */ | |
2471 | void rcu_barrier_bh(void) | |
2472 | { | |
037b64ed | 2473 | _rcu_barrier(&rcu_bh_state); |
d0ec774c PM |
2474 | } |
2475 | EXPORT_SYMBOL_GPL(rcu_barrier_bh); | |
2476 | ||
2477 | /** | |
2478 | * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. | |
2479 | */ | |
2480 | void rcu_barrier_sched(void) | |
2481 | { | |
037b64ed | 2482 | _rcu_barrier(&rcu_sched_state); |
d0ec774c PM |
2483 | } |
2484 | EXPORT_SYMBOL_GPL(rcu_barrier_sched); | |
2485 | ||
64db4cff | 2486 | /* |
27569620 | 2487 | * Do boot-time initialization of a CPU's per-CPU RCU data. |
64db4cff | 2488 | */ |
27569620 PM |
2489 | static void __init |
2490 | rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) | |
64db4cff PM |
2491 | { |
2492 | unsigned long flags; | |
394f99a9 | 2493 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
27569620 PM |
2494 | struct rcu_node *rnp = rcu_get_root(rsp); |
2495 | ||
2496 | /* Set up local state, ensuring consistent view of global state. */ | |
1304afb2 | 2497 | raw_spin_lock_irqsave(&rnp->lock, flags); |
27569620 | 2498 | rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); |
3f5d3ea6 | 2499 | init_callback_list(rdp); |
486e2593 | 2500 | rdp->qlen_lazy = 0; |
1d1fb395 | 2501 | ACCESS_ONCE(rdp->qlen) = 0; |
27569620 | 2502 | rdp->dynticks = &per_cpu(rcu_dynticks, cpu); |
29e37d81 | 2503 | WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE); |
9b2e4f18 | 2504 | WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1); |
27569620 | 2505 | rdp->cpu = cpu; |
d4c08f2a | 2506 | rdp->rsp = rsp; |
1304afb2 | 2507 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27569620 PM |
2508 | } |
2509 | ||
2510 | /* | |
2511 | * Initialize a CPU's per-CPU RCU data. Note that only one online or | |
2512 | * offline event can be happening at a given time. Note also that we | |
2513 | * can accept some slop in the rsp->completed access due to the fact | |
2514 | * that this CPU cannot possibly have any RCU callbacks in flight yet. | |
64db4cff | 2515 | */ |
e4fa4c97 | 2516 | static void __cpuinit |
6cc68793 | 2517 | rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) |
64db4cff PM |
2518 | { |
2519 | unsigned long flags; | |
64db4cff | 2520 | unsigned long mask; |
394f99a9 | 2521 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
64db4cff PM |
2522 | struct rcu_node *rnp = rcu_get_root(rsp); |
2523 | ||
2524 | /* Set up local state, ensuring consistent view of global state. */ | |
1304afb2 | 2525 | raw_spin_lock_irqsave(&rnp->lock, flags); |
64db4cff | 2526 | rdp->beenonline = 1; /* We have now been online. */ |
6cc68793 | 2527 | rdp->preemptible = preemptible; |
37c72e56 PM |
2528 | rdp->qlen_last_fqs_check = 0; |
2529 | rdp->n_force_qs_snap = rsp->n_force_qs; | |
64db4cff | 2530 | rdp->blimit = blimit; |
29e37d81 | 2531 | rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; |
c92b131b PM |
2532 | atomic_set(&rdp->dynticks->dynticks, |
2533 | (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1); | |
7cb92499 | 2534 | rcu_prepare_for_idle_init(cpu); |
1304afb2 | 2535 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
64db4cff PM |
2536 | |
2537 | /* | |
2538 | * A new grace period might start here. If so, we won't be part | |
2539 | * of it, but that is OK, as we are currently in a quiescent state. | |
2540 | */ | |
2541 | ||
2542 | /* Exclude any attempts to start a new GP on large systems. */ | |
1304afb2 | 2543 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
64db4cff PM |
2544 | |
2545 | /* Add CPU to rcu_node bitmasks. */ | |
2546 | rnp = rdp->mynode; | |
2547 | mask = rdp->grpmask; | |
2548 | do { | |
2549 | /* Exclude any attempts to start a new GP on small systems. */ | |
1304afb2 | 2550 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
2551 | rnp->qsmaskinit |= mask; |
2552 | mask = rnp->grpmask; | |
d09b62df | 2553 | if (rnp == rdp->mynode) { |
06ae115a PM |
2554 | /* |
2555 | * If there is a grace period in progress, we will | |
2556 | * set up to wait for it next time we run the | |
2557 | * RCU core code. | |
2558 | */ | |
2559 | rdp->gpnum = rnp->completed; | |
d09b62df | 2560 | rdp->completed = rnp->completed; |
06ae115a PM |
2561 | rdp->passed_quiesce = 0; |
2562 | rdp->qs_pending = 0; | |
e4cc1f22 | 2563 | rdp->passed_quiesce_gpnum = rnp->gpnum - 1; |
d4c08f2a | 2564 | trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuonl"); |
d09b62df | 2565 | } |
1304afb2 | 2566 | raw_spin_unlock(&rnp->lock); /* irqs already disabled. */ |
64db4cff PM |
2567 | rnp = rnp->parent; |
2568 | } while (rnp != NULL && !(rnp->qsmaskinit & mask)); | |
2569 | ||
1304afb2 | 2570 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
64db4cff PM |
2571 | } |
2572 | ||
d72bce0e | 2573 | static void __cpuinit rcu_prepare_cpu(int cpu) |
64db4cff | 2574 | { |
6ce75a23 PM |
2575 | struct rcu_state *rsp; |
2576 | ||
2577 | for_each_rcu_flavor(rsp) | |
2578 | rcu_init_percpu_data(cpu, rsp, | |
2579 | strcmp(rsp->name, "rcu_preempt") == 0); | |
64db4cff PM |
2580 | } |
2581 | ||
2582 | /* | |
f41d911f | 2583 | * Handle CPU online/offline notification events. |
64db4cff | 2584 | */ |
9f680ab4 PM |
2585 | static int __cpuinit rcu_cpu_notify(struct notifier_block *self, |
2586 | unsigned long action, void *hcpu) | |
64db4cff PM |
2587 | { |
2588 | long cpu = (long)hcpu; | |
27f4d280 | 2589 | struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu); |
a26ac245 | 2590 | struct rcu_node *rnp = rdp->mynode; |
6ce75a23 | 2591 | struct rcu_state *rsp; |
64db4cff | 2592 | |
300df91c | 2593 | trace_rcu_utilization("Start CPU hotplug"); |
64db4cff PM |
2594 | switch (action) { |
2595 | case CPU_UP_PREPARE: | |
2596 | case CPU_UP_PREPARE_FROZEN: | |
d72bce0e PZ |
2597 | rcu_prepare_cpu(cpu); |
2598 | rcu_prepare_kthreads(cpu); | |
a26ac245 PM |
2599 | break; |
2600 | case CPU_ONLINE: | |
0f962a5e PM |
2601 | case CPU_DOWN_FAILED: |
2602 | rcu_node_kthread_setaffinity(rnp, -1); | |
e3995a25 | 2603 | rcu_cpu_kthread_setrt(cpu, 1); |
0f962a5e PM |
2604 | break; |
2605 | case CPU_DOWN_PREPARE: | |
2606 | rcu_node_kthread_setaffinity(rnp, cpu); | |
e3995a25 | 2607 | rcu_cpu_kthread_setrt(cpu, 0); |
64db4cff | 2608 | break; |
d0ec774c PM |
2609 | case CPU_DYING: |
2610 | case CPU_DYING_FROZEN: | |
2611 | /* | |
2d999e03 PM |
2612 | * The whole machine is "stopped" except this CPU, so we can |
2613 | * touch any data without introducing corruption. We send the | |
2614 | * dying CPU's callbacks to an arbitrarily chosen online CPU. | |
d0ec774c | 2615 | */ |
6ce75a23 PM |
2616 | for_each_rcu_flavor(rsp) |
2617 | rcu_cleanup_dying_cpu(rsp); | |
7cb92499 | 2618 | rcu_cleanup_after_idle(cpu); |
d0ec774c | 2619 | break; |
64db4cff PM |
2620 | case CPU_DEAD: |
2621 | case CPU_DEAD_FROZEN: | |
2622 | case CPU_UP_CANCELED: | |
2623 | case CPU_UP_CANCELED_FROZEN: | |
6ce75a23 PM |
2624 | for_each_rcu_flavor(rsp) |
2625 | rcu_cleanup_dead_cpu(cpu, rsp); | |
64db4cff PM |
2626 | break; |
2627 | default: | |
2628 | break; | |
2629 | } | |
300df91c | 2630 | trace_rcu_utilization("End CPU hotplug"); |
64db4cff PM |
2631 | return NOTIFY_OK; |
2632 | } | |
2633 | ||
b3dbec76 PM |
2634 | /* |
2635 | * Spawn the kthread that handles this RCU flavor's grace periods. | |
2636 | */ | |
2637 | static int __init rcu_spawn_gp_kthread(void) | |
2638 | { | |
2639 | unsigned long flags; | |
2640 | struct rcu_node *rnp; | |
2641 | struct rcu_state *rsp; | |
2642 | struct task_struct *t; | |
2643 | ||
2644 | for_each_rcu_flavor(rsp) { | |
2645 | t = kthread_run(rcu_gp_kthread, rsp, rsp->name); | |
2646 | BUG_ON(IS_ERR(t)); | |
2647 | rnp = rcu_get_root(rsp); | |
2648 | raw_spin_lock_irqsave(&rnp->lock, flags); | |
2649 | rsp->gp_kthread = t; | |
2650 | raw_spin_unlock_irqrestore(&rnp->lock, flags); | |
2651 | } | |
2652 | return 0; | |
2653 | } | |
2654 | early_initcall(rcu_spawn_gp_kthread); | |
2655 | ||
bbad9379 PM |
2656 | /* |
2657 | * This function is invoked towards the end of the scheduler's initialization | |
2658 | * process. Before this is called, the idle task might contain | |
2659 | * RCU read-side critical sections (during which time, this idle | |
2660 | * task is booting the system). After this function is called, the | |
2661 | * idle tasks are prohibited from containing RCU read-side critical | |
2662 | * sections. This function also enables RCU lockdep checking. | |
2663 | */ | |
2664 | void rcu_scheduler_starting(void) | |
2665 | { | |
2666 | WARN_ON(num_online_cpus() != 1); | |
2667 | WARN_ON(nr_context_switches() > 0); | |
2668 | rcu_scheduler_active = 1; | |
2669 | } | |
2670 | ||
64db4cff PM |
2671 | /* |
2672 | * Compute the per-level fanout, either using the exact fanout specified | |
2673 | * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. | |
2674 | */ | |
2675 | #ifdef CONFIG_RCU_FANOUT_EXACT | |
2676 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
2677 | { | |
2678 | int i; | |
2679 | ||
f885b7f2 | 2680 | for (i = rcu_num_lvls - 1; i > 0; i--) |
64db4cff | 2681 | rsp->levelspread[i] = CONFIG_RCU_FANOUT; |
f885b7f2 | 2682 | rsp->levelspread[0] = rcu_fanout_leaf; |
64db4cff PM |
2683 | } |
2684 | #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
2685 | static void __init rcu_init_levelspread(struct rcu_state *rsp) | |
2686 | { | |
2687 | int ccur; | |
2688 | int cprv; | |
2689 | int i; | |
2690 | ||
2691 | cprv = NR_CPUS; | |
f885b7f2 | 2692 | for (i = rcu_num_lvls - 1; i >= 0; i--) { |
64db4cff PM |
2693 | ccur = rsp->levelcnt[i]; |
2694 | rsp->levelspread[i] = (cprv + ccur - 1) / ccur; | |
2695 | cprv = ccur; | |
2696 | } | |
2697 | } | |
2698 | #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ | |
2699 | ||
2700 | /* | |
2701 | * Helper function for rcu_init() that initializes one rcu_state structure. | |
2702 | */ | |
394f99a9 LJ |
2703 | static void __init rcu_init_one(struct rcu_state *rsp, |
2704 | struct rcu_data __percpu *rda) | |
64db4cff | 2705 | { |
b6407e86 PM |
2706 | static char *buf[] = { "rcu_node_level_0", |
2707 | "rcu_node_level_1", | |
2708 | "rcu_node_level_2", | |
2709 | "rcu_node_level_3" }; /* Match MAX_RCU_LVLS */ | |
64db4cff PM |
2710 | int cpustride = 1; |
2711 | int i; | |
2712 | int j; | |
2713 | struct rcu_node *rnp; | |
2714 | ||
b6407e86 PM |
2715 | BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ |
2716 | ||
64db4cff PM |
2717 | /* Initialize the level-tracking arrays. */ |
2718 | ||
f885b7f2 PM |
2719 | for (i = 0; i < rcu_num_lvls; i++) |
2720 | rsp->levelcnt[i] = num_rcu_lvl[i]; | |
2721 | for (i = 1; i < rcu_num_lvls; i++) | |
64db4cff PM |
2722 | rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; |
2723 | rcu_init_levelspread(rsp); | |
2724 | ||
2725 | /* Initialize the elements themselves, starting from the leaves. */ | |
2726 | ||
f885b7f2 | 2727 | for (i = rcu_num_lvls - 1; i >= 0; i--) { |
64db4cff PM |
2728 | cpustride *= rsp->levelspread[i]; |
2729 | rnp = rsp->level[i]; | |
2730 | for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { | |
1304afb2 | 2731 | raw_spin_lock_init(&rnp->lock); |
b6407e86 PM |
2732 | lockdep_set_class_and_name(&rnp->lock, |
2733 | &rcu_node_class[i], buf[i]); | |
f41d911f | 2734 | rnp->gpnum = 0; |
64db4cff PM |
2735 | rnp->qsmask = 0; |
2736 | rnp->qsmaskinit = 0; | |
2737 | rnp->grplo = j * cpustride; | |
2738 | rnp->grphi = (j + 1) * cpustride - 1; | |
2739 | if (rnp->grphi >= NR_CPUS) | |
2740 | rnp->grphi = NR_CPUS - 1; | |
2741 | if (i == 0) { | |
2742 | rnp->grpnum = 0; | |
2743 | rnp->grpmask = 0; | |
2744 | rnp->parent = NULL; | |
2745 | } else { | |
2746 | rnp->grpnum = j % rsp->levelspread[i - 1]; | |
2747 | rnp->grpmask = 1UL << rnp->grpnum; | |
2748 | rnp->parent = rsp->level[i - 1] + | |
2749 | j / rsp->levelspread[i - 1]; | |
2750 | } | |
2751 | rnp->level = i; | |
12f5f524 | 2752 | INIT_LIST_HEAD(&rnp->blkd_tasks); |
64db4cff PM |
2753 | } |
2754 | } | |
0c34029a | 2755 | |
394f99a9 | 2756 | rsp->rda = rda; |
b3dbec76 | 2757 | init_waitqueue_head(&rsp->gp_wq); |
f885b7f2 | 2758 | rnp = rsp->level[rcu_num_lvls - 1]; |
0c34029a | 2759 | for_each_possible_cpu(i) { |
4a90a068 | 2760 | while (i > rnp->grphi) |
0c34029a | 2761 | rnp++; |
394f99a9 | 2762 | per_cpu_ptr(rsp->rda, i)->mynode = rnp; |
0c34029a LJ |
2763 | rcu_boot_init_percpu_data(i, rsp); |
2764 | } | |
6ce75a23 | 2765 | list_add(&rsp->flavors, &rcu_struct_flavors); |
64db4cff PM |
2766 | } |
2767 | ||
f885b7f2 PM |
2768 | /* |
2769 | * Compute the rcu_node tree geometry from kernel parameters. This cannot | |
2770 | * replace the definitions in rcutree.h because those are needed to size | |
2771 | * the ->node array in the rcu_state structure. | |
2772 | */ | |
2773 | static void __init rcu_init_geometry(void) | |
2774 | { | |
2775 | int i; | |
2776 | int j; | |
cca6f393 | 2777 | int n = nr_cpu_ids; |
f885b7f2 PM |
2778 | int rcu_capacity[MAX_RCU_LVLS + 1]; |
2779 | ||
2780 | /* If the compile-time values are accurate, just leave. */ | |
2781 | if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF) | |
2782 | return; | |
2783 | ||
2784 | /* | |
2785 | * Compute number of nodes that can be handled an rcu_node tree | |
2786 | * with the given number of levels. Setting rcu_capacity[0] makes | |
2787 | * some of the arithmetic easier. | |
2788 | */ | |
2789 | rcu_capacity[0] = 1; | |
2790 | rcu_capacity[1] = rcu_fanout_leaf; | |
2791 | for (i = 2; i <= MAX_RCU_LVLS; i++) | |
2792 | rcu_capacity[i] = rcu_capacity[i - 1] * CONFIG_RCU_FANOUT; | |
2793 | ||
2794 | /* | |
2795 | * The boot-time rcu_fanout_leaf parameter is only permitted | |
2796 | * to increase the leaf-level fanout, not decrease it. Of course, | |
2797 | * the leaf-level fanout cannot exceed the number of bits in | |
2798 | * the rcu_node masks. Finally, the tree must be able to accommodate | |
2799 | * the configured number of CPUs. Complain and fall back to the | |
2800 | * compile-time values if these limits are exceeded. | |
2801 | */ | |
2802 | if (rcu_fanout_leaf < CONFIG_RCU_FANOUT_LEAF || | |
2803 | rcu_fanout_leaf > sizeof(unsigned long) * 8 || | |
2804 | n > rcu_capacity[MAX_RCU_LVLS]) { | |
2805 | WARN_ON(1); | |
2806 | return; | |
2807 | } | |
2808 | ||
2809 | /* Calculate the number of rcu_nodes at each level of the tree. */ | |
2810 | for (i = 1; i <= MAX_RCU_LVLS; i++) | |
2811 | if (n <= rcu_capacity[i]) { | |
2812 | for (j = 0; j <= i; j++) | |
2813 | num_rcu_lvl[j] = | |
2814 | DIV_ROUND_UP(n, rcu_capacity[i - j]); | |
2815 | rcu_num_lvls = i; | |
2816 | for (j = i + 1; j <= MAX_RCU_LVLS; j++) | |
2817 | num_rcu_lvl[j] = 0; | |
2818 | break; | |
2819 | } | |
2820 | ||
2821 | /* Calculate the total number of rcu_node structures. */ | |
2822 | rcu_num_nodes = 0; | |
2823 | for (i = 0; i <= MAX_RCU_LVLS; i++) | |
2824 | rcu_num_nodes += num_rcu_lvl[i]; | |
2825 | rcu_num_nodes -= n; | |
2826 | } | |
2827 | ||
9f680ab4 | 2828 | void __init rcu_init(void) |
64db4cff | 2829 | { |
017c4261 | 2830 | int cpu; |
9f680ab4 | 2831 | |
f41d911f | 2832 | rcu_bootup_announce(); |
f885b7f2 | 2833 | rcu_init_geometry(); |
394f99a9 LJ |
2834 | rcu_init_one(&rcu_sched_state, &rcu_sched_data); |
2835 | rcu_init_one(&rcu_bh_state, &rcu_bh_data); | |
f41d911f | 2836 | __rcu_init_preempt(); |
09223371 | 2837 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
9f680ab4 PM |
2838 | |
2839 | /* | |
2840 | * We don't need protection against CPU-hotplug here because | |
2841 | * this is called early in boot, before either interrupts | |
2842 | * or the scheduler are operational. | |
2843 | */ | |
2844 | cpu_notifier(rcu_cpu_notify, 0); | |
017c4261 PM |
2845 | for_each_online_cpu(cpu) |
2846 | rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); | |
c68de209 | 2847 | check_cpu_stall_init(); |
64db4cff PM |
2848 | } |
2849 | ||
1eba8f84 | 2850 | #include "rcutree_plugin.h" |