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-rw-r--r--kernel/stop_machine.c537
1 files changed, 412 insertions, 125 deletions
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 9bb9fb1bd79..b4e7431e7c7 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -1,17 +1,384 @@
1/* Copyright 2008, 2005 Rusty Russell rusty@rustcorp.com.au IBM Corporation. 1/*
2 * GPL v2 and any later version. 2 * kernel/stop_machine.c
3 *
4 * Copyright (C) 2008, 2005 IBM Corporation.
5 * Copyright (C) 2008, 2005 Rusty Russell rusty@rustcorp.com.au
6 * Copyright (C) 2010 SUSE Linux Products GmbH
7 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
8 *
9 * This file is released under the GPLv2 and any later version.
3 */ 10 */
11#include <linux/completion.h>
4#include <linux/cpu.h> 12#include <linux/cpu.h>
5#include <linux/err.h> 13#include <linux/init.h>
6#include <linux/kthread.h> 14#include <linux/kthread.h>
7#include <linux/module.h> 15#include <linux/module.h>
16#include <linux/percpu.h>
8#include <linux/sched.h> 17#include <linux/sched.h>
9#include <linux/stop_machine.h> 18#include <linux/stop_machine.h>
10#include <linux/syscalls.h>
11#include <linux/interrupt.h> 19#include <linux/interrupt.h>
20#include <linux/kallsyms.h>
12 21
13#include <asm/atomic.h> 22#include <asm/atomic.h>
14#include <asm/uaccess.h> 23
24/*
25 * Structure to determine completion condition and record errors. May
26 * be shared by works on different cpus.
27 */
28struct cpu_stop_done {
29 atomic_t nr_todo; /* nr left to execute */
30 bool executed; /* actually executed? */
31 int ret; /* collected return value */
32 struct completion completion; /* fired if nr_todo reaches 0 */
33};
34
35/* the actual stopper, one per every possible cpu, enabled on online cpus */
36struct cpu_stopper {
37 spinlock_t lock;
38 struct list_head works; /* list of pending works */
39 struct task_struct *thread; /* stopper thread */
40 bool enabled; /* is this stopper enabled? */
41};
42
43static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper);
44
45static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo)
46{
47 memset(done, 0, sizeof(*done));
48 atomic_set(&done->nr_todo, nr_todo);
49 init_completion(&done->completion);
50}
51
52/* signal completion unless @done is NULL */
53static void cpu_stop_signal_done(struct cpu_stop_done *done, bool executed)
54{
55 if (done) {
56 if (executed)
57 done->executed = true;
58 if (atomic_dec_and_test(&done->nr_todo))
59 complete(&done->completion);
60 }
61}
62
63/* queue @work to @stopper. if offline, @work is completed immediately */
64static void cpu_stop_queue_work(struct cpu_stopper *stopper,
65 struct cpu_stop_work *work)
66{
67 unsigned long flags;
68
69 spin_lock_irqsave(&stopper->lock, flags);
70
71 if (stopper->enabled) {
72 list_add_tail(&work->list, &stopper->works);
73 wake_up_process(stopper->thread);
74 } else
75 cpu_stop_signal_done(work->done, false);
76
77 spin_unlock_irqrestore(&stopper->lock, flags);
78}
79
80/**
81 * stop_one_cpu - stop a cpu
82 * @cpu: cpu to stop
83 * @fn: function to execute
84 * @arg: argument to @fn
85 *
86 * Execute @fn(@arg) on @cpu. @fn is run in a process context with
87 * the highest priority preempting any task on the cpu and
88 * monopolizing it. This function returns after the execution is
89 * complete.
90 *
91 * This function doesn't guarantee @cpu stays online till @fn
92 * completes. If @cpu goes down in the middle, execution may happen
93 * partially or fully on different cpus. @fn should either be ready
94 * for that or the caller should ensure that @cpu stays online until
95 * this function completes.
96 *
97 * CONTEXT:
98 * Might sleep.
99 *
100 * RETURNS:
101 * -ENOENT if @fn(@arg) was not executed because @cpu was offline;
102 * otherwise, the return value of @fn.
103 */
104int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
105{
106 struct cpu_stop_done done;
107 struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done };
108
109 cpu_stop_init_done(&done, 1);
110 cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu), &work);
111 wait_for_completion(&done.completion);
112 return done.executed ? done.ret : -ENOENT;
113}
114
115/**
116 * stop_one_cpu_nowait - stop a cpu but don't wait for completion
117 * @cpu: cpu to stop
118 * @fn: function to execute
119 * @arg: argument to @fn
120 *
121 * Similar to stop_one_cpu() but doesn't wait for completion. The
122 * caller is responsible for ensuring @work_buf is currently unused
123 * and will remain untouched until stopper starts executing @fn.
124 *
125 * CONTEXT:
126 * Don't care.
127 */
128void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
129 struct cpu_stop_work *work_buf)
130{
131 *work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, };
132 cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu), work_buf);
133}
134
135/* static data for stop_cpus */
136static DEFINE_MUTEX(stop_cpus_mutex);
137static DEFINE_PER_CPU(struct cpu_stop_work, stop_cpus_work);
138
139int __stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
140{
141 struct cpu_stop_work *work;
142 struct cpu_stop_done done;
143 unsigned int cpu;
144
145 /* initialize works and done */
146 for_each_cpu(cpu, cpumask) {
147 work = &per_cpu(stop_cpus_work, cpu);
148 work->fn = fn;
149 work->arg = arg;
150 work->done = &done;
151 }
152 cpu_stop_init_done(&done, cpumask_weight(cpumask));
153
154 /*
155 * Disable preemption while queueing to avoid getting
156 * preempted by a stopper which might wait for other stoppers
157 * to enter @fn which can lead to deadlock.
158 */
159 preempt_disable();
160 for_each_cpu(cpu, cpumask)
161 cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu),
162 &per_cpu(stop_cpus_work, cpu));
163 preempt_enable();
164
165 wait_for_completion(&done.completion);
166 return done.executed ? done.ret : -ENOENT;
167}
168
169/**
170 * stop_cpus - stop multiple cpus
171 * @cpumask: cpus to stop
172 * @fn: function to execute
173 * @arg: argument to @fn
174 *
175 * Execute @fn(@arg) on online cpus in @cpumask. On each target cpu,
176 * @fn is run in a process context with the highest priority
177 * preempting any task on the cpu and monopolizing it. This function
178 * returns after all executions are complete.
179 *
180 * This function doesn't guarantee the cpus in @cpumask stay online
181 * till @fn completes. If some cpus go down in the middle, execution
182 * on the cpu may happen partially or fully on different cpus. @fn
183 * should either be ready for that or the caller should ensure that
184 * the cpus stay online until this function completes.
185 *
186 * All stop_cpus() calls are serialized making it safe for @fn to wait
187 * for all cpus to start executing it.
188 *
189 * CONTEXT:
190 * Might sleep.
191 *
192 * RETURNS:
193 * -ENOENT if @fn(@arg) was not executed at all because all cpus in
194 * @cpumask were offline; otherwise, 0 if all executions of @fn
195 * returned 0, any non zero return value if any returned non zero.
196 */
197int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
198{
199 int ret;
200
201 /* static works are used, process one request at a time */
202 mutex_lock(&stop_cpus_mutex);
203 ret = __stop_cpus(cpumask, fn, arg);
204 mutex_unlock(&stop_cpus_mutex);
205 return ret;
206}
207
208/**
209 * try_stop_cpus - try to stop multiple cpus
210 * @cpumask: cpus to stop
211 * @fn: function to execute
212 * @arg: argument to @fn
213 *
214 * Identical to stop_cpus() except that it fails with -EAGAIN if
215 * someone else is already using the facility.
216 *
217 * CONTEXT:
218 * Might sleep.
219 *
220 * RETURNS:
221 * -EAGAIN if someone else is already stopping cpus, -ENOENT if
222 * @fn(@arg) was not executed at all because all cpus in @cpumask were
223 * offline; otherwise, 0 if all executions of @fn returned 0, any non
224 * zero return value if any returned non zero.
225 */
226int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
227{
228 int ret;
229
230 /* static works are used, process one request at a time */
231 if (!mutex_trylock(&stop_cpus_mutex))
232 return -EAGAIN;
233 ret = __stop_cpus(cpumask, fn, arg);
234 mutex_unlock(&stop_cpus_mutex);
235 return ret;
236}
237
238static int cpu_stopper_thread(void *data)
239{
240 struct cpu_stopper *stopper = data;
241 struct cpu_stop_work *work;
242 int ret;
243
244repeat:
245 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
246
247 if (kthread_should_stop()) {
248 __set_current_state(TASK_RUNNING);
249 return 0;
250 }
251
252 work = NULL;
253 spin_lock_irq(&stopper->lock);
254 if (!list_empty(&stopper->works)) {
255 work = list_first_entry(&stopper->works,
256 struct cpu_stop_work, list);
257 list_del_init(&work->list);
258 }
259 spin_unlock_irq(&stopper->lock);
260
261 if (work) {
262 cpu_stop_fn_t fn = work->fn;
263 void *arg = work->arg;
264 struct cpu_stop_done *done = work->done;
265 char ksym_buf[KSYM_NAME_LEN];
266
267 __set_current_state(TASK_RUNNING);
268
269 /* cpu stop callbacks are not allowed to sleep */
270 preempt_disable();
271
272 ret = fn(arg);
273 if (ret)
274 done->ret = ret;
275
276 /* restore preemption and check it's still balanced */
277 preempt_enable();
278 WARN_ONCE(preempt_count(),
279 "cpu_stop: %s(%p) leaked preempt count\n",
280 kallsyms_lookup((unsigned long)fn, NULL, NULL, NULL,
281 ksym_buf), arg);
282
283 cpu_stop_signal_done(done, true);
284 } else
285 schedule();
286
287 goto repeat;
288}
289
290/* manage stopper for a cpu, mostly lifted from sched migration thread mgmt */
291static int __cpuinit cpu_stop_cpu_callback(struct notifier_block *nfb,
292 unsigned long action, void *hcpu)
293{
294 struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
295 unsigned int cpu = (unsigned long)hcpu;
296 struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
297 struct task_struct *p;
298
299 switch (action & ~CPU_TASKS_FROZEN) {
300 case CPU_UP_PREPARE:
301 BUG_ON(stopper->thread || stopper->enabled ||
302 !list_empty(&stopper->works));
303 p = kthread_create(cpu_stopper_thread, stopper, "migration/%d",
304 cpu);
305 if (IS_ERR(p))
306 return NOTIFY_BAD;
307 sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
308 get_task_struct(p);
309 stopper->thread = p;
310 break;
311
312 case CPU_ONLINE:
313 kthread_bind(stopper->thread, cpu);
314 /* strictly unnecessary, as first user will wake it */
315 wake_up_process(stopper->thread);
316 /* mark enabled */
317 spin_lock_irq(&stopper->lock);
318 stopper->enabled = true;
319 spin_unlock_irq(&stopper->lock);
320 break;
321
322#ifdef CONFIG_HOTPLUG_CPU
323 case CPU_UP_CANCELED:
324 case CPU_DEAD:
325 {
326 struct cpu_stop_work *work;
327
328 /* kill the stopper */
329 kthread_stop(stopper->thread);
330 /* drain remaining works */
331 spin_lock_irq(&stopper->lock);
332 list_for_each_entry(work, &stopper->works, list)
333 cpu_stop_signal_done(work->done, false);
334 stopper->enabled = false;
335 spin_unlock_irq(&stopper->lock);
336 /* release the stopper */
337 put_task_struct(stopper->thread);
338 stopper->thread = NULL;
339 break;
340 }
341#endif
342 }
343
344 return NOTIFY_OK;
345}
346
347/*
348 * Give it a higher priority so that cpu stopper is available to other
349 * cpu notifiers. It currently shares the same priority as sched
350 * migration_notifier.
351 */
352static struct notifier_block __cpuinitdata cpu_stop_cpu_notifier = {
353 .notifier_call = cpu_stop_cpu_callback,
354 .priority = 10,
355};
356
357static int __init cpu_stop_init(void)
358{
359 void *bcpu = (void *)(long)smp_processor_id();
360 unsigned int cpu;
361 int err;
362
363 for_each_possible_cpu(cpu) {
364 struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
365
366 spin_lock_init(&stopper->lock);
367 INIT_LIST_HEAD(&stopper->works);
368 }
369
370 /* start one for the boot cpu */
371 err = cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_UP_PREPARE,
372 bcpu);
373 BUG_ON(err == NOTIFY_BAD);
374 cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_ONLINE, bcpu);
375 register_cpu_notifier(&cpu_stop_cpu_notifier);
376
377 return 0;
378}
379early_initcall(cpu_stop_init);
380
381#ifdef CONFIG_STOP_MACHINE
15 382
16/* This controls the threads on each CPU. */ 383/* This controls the threads on each CPU. */
17enum stopmachine_state { 384enum stopmachine_state {
@@ -26,174 +393,94 @@ enum stopmachine_state {
26 /* Exit */ 393 /* Exit */
27 STOPMACHINE_EXIT, 394 STOPMACHINE_EXIT,
28}; 395};
29static enum stopmachine_state state;
30 396
31struct stop_machine_data { 397struct stop_machine_data {
32 int (*fn)(void *); 398 int (*fn)(void *);
33 void *data; 399 void *data;
34 int fnret; 400 /* Like num_online_cpus(), but hotplug cpu uses us, so we need this. */
401 unsigned int num_threads;
402 const struct cpumask *active_cpus;
403
404 enum stopmachine_state state;
405 atomic_t thread_ack;
35}; 406};
36 407
37/* Like num_online_cpus(), but hotplug cpu uses us, so we need this. */ 408static void set_state(struct stop_machine_data *smdata,
38static unsigned int num_threads; 409 enum stopmachine_state newstate)
39static atomic_t thread_ack;
40static DEFINE_MUTEX(lock);
41/* setup_lock protects refcount, stop_machine_wq and stop_machine_work. */
42static DEFINE_MUTEX(setup_lock);
43/* Users of stop_machine. */
44static int refcount;
45static struct workqueue_struct *stop_machine_wq;
46static struct stop_machine_data active, idle;
47static const struct cpumask *active_cpus;
48static void __percpu *stop_machine_work;
49
50static void set_state(enum stopmachine_state newstate)
51{ 410{
52 /* Reset ack counter. */ 411 /* Reset ack counter. */
53 atomic_set(&thread_ack, num_threads); 412 atomic_set(&smdata->thread_ack, smdata->num_threads);
54 smp_wmb(); 413 smp_wmb();
55 state = newstate; 414 smdata->state = newstate;
56} 415}
57 416
58/* Last one to ack a state moves to the next state. */ 417/* Last one to ack a state moves to the next state. */
59static void ack_state(void) 418static void ack_state(struct stop_machine_data *smdata)
60{ 419{
61 if (atomic_dec_and_test(&thread_ack)) 420 if (atomic_dec_and_test(&smdata->thread_ack))
62 set_state(state + 1); 421 set_state(smdata, smdata->state + 1);
63} 422}
64 423
65/* This is the actual function which stops the CPU. It runs 424/* This is the cpu_stop function which stops the CPU. */
66 * in the context of a dedicated stopmachine workqueue. */ 425static int stop_machine_cpu_stop(void *data)
67static void stop_cpu(struct work_struct *unused)
68{ 426{
427 struct stop_machine_data *smdata = data;
69 enum stopmachine_state curstate = STOPMACHINE_NONE; 428 enum stopmachine_state curstate = STOPMACHINE_NONE;
70 struct stop_machine_data *smdata = &idle; 429 int cpu = smp_processor_id(), err = 0;
71 int cpu = smp_processor_id(); 430 bool is_active;
72 int err; 431
432 if (!smdata->active_cpus)
433 is_active = cpu == cpumask_first(cpu_online_mask);
434 else
435 is_active = cpumask_test_cpu(cpu, smdata->active_cpus);
73 436
74 if (!active_cpus) {
75 if (cpu == cpumask_first(cpu_online_mask))
76 smdata = &active;
77 } else {
78 if (cpumask_test_cpu(cpu, active_cpus))
79 smdata = &active;
80 }
81 /* Simple state machine */ 437 /* Simple state machine */
82 do { 438 do {
83 /* Chill out and ensure we re-read stopmachine_state. */ 439 /* Chill out and ensure we re-read stopmachine_state. */
84 cpu_relax(); 440 cpu_relax();
85 if (state != curstate) { 441 if (smdata->state != curstate) {
86 curstate = state; 442 curstate = smdata->state;
87 switch (curstate) { 443 switch (curstate) {
88 case STOPMACHINE_DISABLE_IRQ: 444 case STOPMACHINE_DISABLE_IRQ:
89 local_irq_disable(); 445 local_irq_disable();
90 hard_irq_disable(); 446 hard_irq_disable();
91 break; 447 break;
92 case STOPMACHINE_RUN: 448 case STOPMACHINE_RUN:
93 /* On multiple CPUs only a single error code 449 if (is_active)
94 * is needed to tell that something failed. */ 450 err = smdata->fn(smdata->data);
95 err = smdata->fn(smdata->data);
96 if (err)
97 smdata->fnret = err;
98 break; 451 break;
99 default: 452 default:
100 break; 453 break;
101 } 454 }
102 ack_state(); 455 ack_state(smdata);
103 } 456 }
104 } while (curstate != STOPMACHINE_EXIT); 457 } while (curstate != STOPMACHINE_EXIT);
105 458
106 local_irq_enable(); 459 local_irq_enable();
460 return err;
107} 461}
108 462
109/* Callback for CPUs which aren't supposed to do anything. */
110static int chill(void *unused)
111{
112 return 0;
113}
114
115int stop_machine_create(void)
116{
117 mutex_lock(&setup_lock);
118 if (refcount)
119 goto done;
120 stop_machine_wq = create_rt_workqueue("kstop");
121 if (!stop_machine_wq)
122 goto err_out;
123 stop_machine_work = alloc_percpu(struct work_struct);
124 if (!stop_machine_work)
125 goto err_out;
126done:
127 refcount++;
128 mutex_unlock(&setup_lock);
129 return 0;
130
131err_out:
132 if (stop_machine_wq)
133 destroy_workqueue(stop_machine_wq);
134 mutex_unlock(&setup_lock);
135 return -ENOMEM;
136}
137EXPORT_SYMBOL_GPL(stop_machine_create);
138
139void stop_machine_destroy(void)
140{
141 mutex_lock(&setup_lock);
142 refcount--;
143 if (refcount)
144 goto done;
145 destroy_workqueue(stop_machine_wq);
146 free_percpu(stop_machine_work);
147done:
148 mutex_unlock(&setup_lock);
149}
150EXPORT_SYMBOL_GPL(stop_machine_destroy);
151
152int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus) 463int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus)
153{ 464{
154 struct work_struct *sm_work; 465 struct stop_machine_data smdata = { .fn = fn, .data = data,
155 int i, ret; 466 .num_threads = num_online_cpus(),
156 467 .active_cpus = cpus };
157 /* Set up initial state. */ 468
158 mutex_lock(&lock); 469 /* Set the initial state and stop all online cpus. */
159 num_threads = num_online_cpus(); 470 set_state(&smdata, STOPMACHINE_PREPARE);
160 active_cpus = cpus; 471 return stop_cpus(cpu_online_mask, stop_machine_cpu_stop, &smdata);
161 active.fn = fn;
162 active.data = data;
163 active.fnret = 0;
164 idle.fn = chill;
165 idle.data = NULL;
166
167 set_state(STOPMACHINE_PREPARE);
168
169 /* Schedule the stop_cpu work on all cpus: hold this CPU so one
170 * doesn't hit this CPU until we're ready. */
171 get_cpu();
172 for_each_online_cpu(i) {
173 sm_work = per_cpu_ptr(stop_machine_work, i);
174 INIT_WORK(sm_work, stop_cpu);
175 queue_work_on(i, stop_machine_wq, sm_work);
176 }
177 /* This will release the thread on our CPU. */
178 put_cpu();
179 flush_workqueue(stop_machine_wq);
180 ret = active.fnret;
181 mutex_unlock(&lock);
182 return ret;
183} 472}
184 473
185int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus) 474int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus)
186{ 475{
187 int ret; 476 int ret;
188 477
189 ret = stop_machine_create();
190 if (ret)
191 return ret;
192 /* No CPUs can come up or down during this. */ 478 /* No CPUs can come up or down during this. */
193 get_online_cpus(); 479 get_online_cpus();
194 ret = __stop_machine(fn, data, cpus); 480 ret = __stop_machine(fn, data, cpus);
195 put_online_cpus(); 481 put_online_cpus();
196 stop_machine_destroy();
197 return ret; 482 return ret;
198} 483}
199EXPORT_SYMBOL_GPL(stop_machine); 484EXPORT_SYMBOL_GPL(stop_machine);
485
486#endif /* CONFIG_STOP_MACHINE */