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workqueue: don't clear cwq->thread until it exits 

Pointed out by Srivatsa Vaddagiri.

cleanup_workqueue_thread() sets cwq->thread = NULL and does kthread_stop().
This breaks the "if (cwq->thread == current)" logic in flush_cpu_workqueue()
and leads to deadlock.

Kill the thead first, then clear cwq->thread. workqueue_mutex protects us
from create_workqueue_thread() so we don't need cwq->lock.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>
Cc: Gautham shenoy <ego@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2007-05-09 02:34:08 -07:00 committed by Linus Torvalds
parent d721304dce
commit 36aa9dfc39
1 changed files with 5 additions and 10 deletions
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15
kernel/workqueue.c
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@ -625,17 +625,12 @@ EXPORT_SYMBOL_GPL(__create_workqueue);
static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
{
struct cpu_workqueue_struct *cwq;
unsigned long flags;
struct task_struct *p;
struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
cwq = per_cpu_ptr(wq->cpu_wq, cpu);
spin_lock_irqsave(&cwq->lock, flags);
p = cwq->thread;
cwq->thread = NULL;
spin_unlock_irqrestore(&cwq->lock, flags);
if (p)
kthread_stop(p);
if (cwq->thread) {
kthread_stop(cwq->thread);
cwq->thread = NULL;
}
}
/**