diff options
author | Oleg Nesterov <oleg@tv-sign.ru> | 2007-07-17 04:03:55 -0700 |
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committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-07-17 10:23:03 -0700 |
commit | 13c22168b7276dffe49dc66675d5a78f6d288e0d (patch) | |
tree | 4062929954f04db9c24be08cba94a0ed6e7fd65f /kernel/workqueue.c | |
parent | 87a7defb0d4255d5aea2c5067813b26836127983 (diff) | |
download | linux-13c22168b7276dffe49dc66675d5a78f6d288e0d.tar.bz2 |
destroy_workqueue() can livelock
Pointed out by Michal Schmidt <mschmidt@redhat.com>.
The bug was introduced in 2.6.22 by me.
cleanup_workqueue_thread() does flush_cpu_workqueue(cwq) in a loop until
->worklist becomes empty. This is live-lockable, a re-niced caller can get
CPU after wake_up() and insert a new barrier before the lower-priority
cwq->thread has a chance to clear ->current_work.
Change cleanup_workqueue_thread() to do flush_cpu_workqueue(cwq) only once.
We can rely on the fact that run_workqueue() won't return until it flushes
all works. So it is safe to call kthread_stop() after that, the "should
stop" request won't be noticed until run_workqueue() returns.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Michal Schmidt <mschmidt@redhat.com>
Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/workqueue.c')
-rw-r--r-- | kernel/workqueue.c | 11 |
1 files changed, 5 insertions, 6 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 1935302cc645..58e5c152a6bb 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -752,18 +752,17 @@ static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu) if (cwq->thread == NULL) return; + flush_cpu_workqueue(cwq); /* - * If the caller is CPU_DEAD the single flush_cpu_workqueue() - * is not enough, a concurrent flush_workqueue() can insert a - * barrier after us. + * If the caller is CPU_DEAD and cwq->worklist was not empty, + * a concurrent flush_workqueue() can insert a barrier after us. + * However, in that case run_workqueue() won't return and check + * kthread_should_stop() until it flushes all work_struct's. * When ->worklist becomes empty it is safe to exit because no * more work_structs can be queued on this cwq: flush_workqueue * checks list_empty(), and a "normal" queue_work() can't use * a dead CPU. */ - while (flush_cpu_workqueue(cwq)) - ; - kthread_stop(cwq->thread); cwq->thread = NULL; } |