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Commit 9b41ea72 authored by Andrew Morton's avatar Andrew Morton Committed by Greg Kroah-Hartman
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[PATCH] workqueue: remove lock_cpu_hotplug() 



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: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 2b257425

kernel/workqueue.c

+21 −12
Original line number Diff line number Diff line
@@ -68,7 +68,7 @@ struct workqueue_struct { 


/* All the per-cpu workqueues on the system, for hotplug cpu to add/remove

   threads to each one as cpus come/go. */

static DEFINE_SPINLOCK(workqueue_lock);

static DEFINE_MUTEX(workqueue_mutex);

static LIST_HEAD(workqueues);



static int singlethread_cpu;
@@ -320,10 +320,10 @@ void fastcall flush_workqueue(struct workqueue_struct *wq) 
	} else {

		int cpu;



		lock_cpu_hotplug();

		mutex_lock(&workqueue_mutex);

		for_each_online_cpu(cpu)

			flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));

		unlock_cpu_hotplug();

		mutex_unlock(&workqueue_mutex);

	}

}

EXPORT_SYMBOL_GPL(flush_workqueue);
@@ -371,8 +371,7 @@ struct workqueue_struct *__create_workqueue(const char *name, 
	}



	wq->name = name;

	/* We don't need the distraction of CPUs appearing and vanishing. */

	lock_cpu_hotplug();

	mutex_lock(&workqueue_mutex);

	if (singlethread) {

		INIT_LIST_HEAD(&wq->list);

		p = create_workqueue_thread(wq, singlethread_cpu);
@@ -381,9 +380,7 @@ struct workqueue_struct *__create_workqueue(const char *name, 
		else

			wake_up_process(p);

	} else {

		spin_lock(&workqueue_lock);

		list_add(&wq->list, &workqueues);

		spin_unlock(&workqueue_lock);

		for_each_online_cpu(cpu) {

			p = create_workqueue_thread(wq, cpu);

			if (p) {
@@ -393,7 +390,7 @@ struct workqueue_struct *__create_workqueue(const char *name, 
				destroy = 1;

		}

	}

	unlock_cpu_hotplug();

	mutex_unlock(&workqueue_mutex);



	/*

	 * 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);



	/* We don't need the distraction of CPUs appearing and vanishing. */

	lock_cpu_hotplug();

	mutex_lock(&workqueue_mutex);

	if (is_single_threaded(wq))

		cleanup_workqueue_thread(wq, singlethread_cpu);

	else {

		for_each_online_cpu(cpu)

			cleanup_workqueue_thread(wq, cpu);

		spin_lock(&workqueue_lock);

		list_del(&wq->list);

		spin_unlock(&workqueue_lock);

	}

	unlock_cpu_hotplug();

	mutex_unlock(&workqueue_mutex);

	free_percpu(wq->cpu_wq);

	kfree(wq);

}
@@ -515,11 +510,13 @@ int schedule_on_each_cpu(void (*func)(void *info), void *info) 
	if (!works)

		return -ENOMEM;



	mutex_lock(&workqueue_mutex);

	for_each_online_cpu(cpu) {

		INIT_WORK(per_cpu_ptr(works, cpu), func, info);

		__queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu),

				per_cpu_ptr(works, cpu));

	}

	mutex_unlock(&workqueue_mutex);

	flush_workqueue(keventd_wq);

	free_percpu(works);

	return 0;
@@ -635,6 +632,7 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb, 


	switch (action) {

	case CPU_UP_PREPARE:

		mutex_lock(&workqueue_mutex);

		/* Create a new workqueue thread for it. */

		list_for_each_entry(wq, &workqueues, list) {

			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);

			wake_up_process(cwq->thread);

		}

		mutex_unlock(&workqueue_mutex);

		break;



	case CPU_UP_CANCELED:
@@ -664,6 +663,15 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb, 
				     any_online_cpu(cpu_online_map));

			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;



	case CPU_DEAD:
@@ -671,6 +679,7 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb, 
			cleanup_workqueue_thread(wq, hotcpu);

		list_for_each_entry(wq, &workqueues, list)

			take_over_work(wq, hotcpu);

		mutex_unlock(&workqueue_mutex);

		break;

	}