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| author | Tejun Heo <tj@kernel.org> | 2012-05-14 15:04:50 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-06-01 15:12:56 +0800 |
| commit | 935055856458a05c43f518bf9ed406f67c090f0a (patch) | |
| tree | 3cde458e723b77008d8dc041de6632458f4cba58 /kernel | |
| parent | bfd6d6af769c5cd62aa9ed75b038ea3d234b090b (diff) | |
| download | lwn-935055856458a05c43f518bf9ed406f67c090f0a.tar.gz lwn-935055856458a05c43f518bf9ed406f67c090f0a.zip | |
workqueue: skip nr_running sanity check in worker_enter_idle() if trustee is active
commit 544ecf310f0e7f51fa057ac2a295fc1b3b35a9d3 upstream.
worker_enter_idle() has WARN_ON_ONCE() which triggers if nr_running
isn't zero when every worker is idle. This can trigger spuriously
while a cpu is going down due to the way trustee sets %WORKER_ROGUE
and zaps nr_running.
It first sets %WORKER_ROGUE on all workers without updating
nr_running, releases gcwq->lock, schedules, regrabs gcwq->lock and
then zaps nr_running. If the last running worker enters idle
inbetween, it would see stale nr_running which hasn't been zapped yet
and trigger the WARN_ON_ONCE().
Fix it by performing the sanity check iff the trustee is idle.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/workqueue.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 1456daba9a08..ee1845b8d690 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1214,8 +1214,13 @@ static void worker_enter_idle(struct worker *worker) } else wake_up_all(&gcwq->trustee_wait); - /* sanity check nr_running */ - WARN_ON_ONCE(gcwq->nr_workers == gcwq->nr_idle && + /* + * Sanity check nr_running. Because trustee releases gcwq->lock + * between setting %WORKER_ROGUE and zapping nr_running, the + * warning may trigger spuriously. Check iff trustee is idle. + */ + WARN_ON_ONCE(gcwq->trustee_state == TRUSTEE_DONE && + gcwq->nr_workers == gcwq->nr_idle && atomic_read(get_gcwq_nr_running(gcwq->cpu))); } |