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[PATCH] workqueue: remove lock_cpu_hotplug()

Browse source 
Use a private lock instead.  It protects all per-cpu data structures in
workqueue.c, including the workqueues list.

Fix a bug in schedule_on_each_cpu(): it was forgetting to lock down the
per-cpu resources.

Unfixed long-standing bug: if someone unplugs the CPU identified by
`singlethread_cpu' the kernel will get very sick.

Cc: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Andrew Morton 2006-08-13 23:24:26 -07:00 committed by Greg Kroah-Hartman
parent 2b25742556
commit 9b41ea7289
1 changed files with 21 additions and 12 deletions
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33
kernel/workqueue.c
View file

@ -68,7 +68,7 @@ struct workqueue_struct {
/* All the per-cpu workqueues on the system, for hotplug cpu to add/remove /* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
threads to each one as cpus come/go. */ threads to each one as cpus come/go. */
static DEFINE_SPINLOCK(workqueue_lock); static DEFINE_MUTEX(workqueue_mutex);
static LIST_HEAD(workqueues); static LIST_HEAD(workqueues);
static int singlethread_cpu; static int singlethread_cpu;
@ -320,10 +320,10 @@ void fastcall flush_workqueue(struct workqueue_struct *wq)
} else { } else {
int cpu; int cpu;
lock_cpu_hotplug(); mutex_lock(&workqueue_mutex);
for_each_online_cpu(cpu) for_each_online_cpu(cpu)
flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu)); flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
unlock_cpu_hotplug(); mutex_unlock(&workqueue_mutex);
} }
} }
EXPORT_SYMBOL_GPL(flush_workqueue); EXPORT_SYMBOL_GPL(flush_workqueue);
@ -371,8 +371,7 @@ struct workqueue_struct *__create_workqueue(const char *name,
} }
wq->name = name; wq->name = name;
/* We don't need the distraction of CPUs appearing and vanishing. */ mutex_lock(&workqueue_mutex);
lock_cpu_hotplug();
if (singlethread) { if (singlethread) {
INIT_LIST_HEAD(&wq->list); INIT_LIST_HEAD(&wq->list);
p = create_workqueue_thread(wq, singlethread_cpu); p = create_workqueue_thread(wq, singlethread_cpu);
@ -381,9 +380,7 @@ struct workqueue_struct *__create_workqueue(const char *name,
else else
wake_up_process(p); wake_up_process(p);
} else { } else {
spin_lock(&workqueue_lock);
list_add(&wq->list, &workqueues); list_add(&wq->list, &workqueues);
spin_unlock(&workqueue_lock);
for_each_online_cpu(cpu) { for_each_online_cpu(cpu) {
p = create_workqueue_thread(wq, cpu); p = create_workqueue_thread(wq, cpu);
if (p) { if (p) {
@ -393,7 +390,7 @@ struct workqueue_struct *__create_workqueue(const char *name,
destroy = 1; destroy = 1;
} }
} }
unlock_cpu_hotplug(); mutex_unlock(&workqueue_mutex);
/* /*
* Was there any error during startup? If yes then clean up: * Was there any error during startup? If yes then clean up:
@ -434,17 +431,15 @@ void destroy_workqueue(struct workqueue_struct *wq)
flush_workqueue(wq); flush_workqueue(wq);
/* We don't need the distraction of CPUs appearing and vanishing. */ /* We don't need the distraction of CPUs appearing and vanishing. */
lock_cpu_hotplug(); mutex_lock(&workqueue_mutex);
if (is_single_threaded(wq)) if (is_single_threaded(wq))
cleanup_workqueue_thread(wq, singlethread_cpu); cleanup_workqueue_thread(wq, singlethread_cpu);
else { else {
for_each_online_cpu(cpu) for_each_online_cpu(cpu)
cleanup_workqueue_thread(wq, cpu); cleanup_workqueue_thread(wq, cpu);
spin_lock(&workqueue_lock);
list_del(&wq->list); list_del(&wq->list);
spin_unlock(&workqueue_lock);
} }
unlock_cpu_hotplug(); mutex_unlock(&workqueue_mutex);
free_percpu(wq->cpu_wq); free_percpu(wq->cpu_wq);
kfree(wq); kfree(wq);
} }
@ -515,11 +510,13 @@ int schedule_on_each_cpu(void (*func)(void *info), void *info)
if (!works) if (!works)
return -ENOMEM; return -ENOMEM;
mutex_lock(&workqueue_mutex);
for_each_online_cpu(cpu) { for_each_online_cpu(cpu) {
INIT_WORK(per_cpu_ptr(works, cpu), func, info); INIT_WORK(per_cpu_ptr(works, cpu), func, info);
__queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu), __queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu),
per_cpu_ptr(works, cpu)); per_cpu_ptr(works, cpu));
} }
mutex_unlock(&workqueue_mutex);
flush_workqueue(keventd_wq); flush_workqueue(keventd_wq);
free_percpu(works); free_percpu(works);
return 0; return 0;
@ -635,6 +632,7 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
switch (action) { switch (action) {
case CPU_UP_PREPARE: case CPU_UP_PREPARE:
mutex_lock(&workqueue_mutex);
/* Create a new workqueue thread for it. */ /* Create a new workqueue thread for it. */
list_for_each_entry(wq, &workqueues, list) { list_for_each_entry(wq, &workqueues, list) {
if (!create_workqueue_thread(wq, hotcpu)) { if (!create_workqueue_thread(wq, hotcpu)) {
@ -653,6 +651,7 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
kthread_bind(cwq->thread, hotcpu); kthread_bind(cwq->thread, hotcpu);
wake_up_process(cwq->thread); wake_up_process(cwq->thread);
} }
mutex_unlock(&workqueue_mutex);
break; break;
case CPU_UP_CANCELED: case CPU_UP_CANCELED:
@ -664,6 +663,15 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
any_online_cpu(cpu_online_map)); any_online_cpu(cpu_online_map));
cleanup_workqueue_thread(wq, hotcpu); cleanup_workqueue_thread(wq, hotcpu);
} }
mutex_unlock(&workqueue_mutex);
break;
case CPU_DOWN_PREPARE:
mutex_lock(&workqueue_mutex);
break;
case CPU_DOWN_FAILED:
mutex_unlock(&workqueue_mutex);
break; break;
case CPU_DEAD: case CPU_DEAD:
@ -671,6 +679,7 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
cleanup_workqueue_thread(wq, hotcpu); cleanup_workqueue_thread(wq, hotcpu);
list_for_each_entry(wq, &workqueues, list) list_for_each_entry(wq, &workqueues, list)
take_over_work(wq, hotcpu); take_over_work(wq, hotcpu);
mutex_unlock(&workqueue_mutex);
break; break;
} }