This is a note to let you know that I've just added the patch titled
workqueue: skip nr_running sanity check in worker_enter_idle() if trustee
is active
to the 3.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
workqueue-skip-nr_running-sanity-check-in-worker_enter_idle-if-trustee-is-active.patch
and it can be found in the queue-3.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 544ecf310f0e7f51fa057ac2a295fc1b3b35a9d3 Mon Sep 17 00:00:00 2001
From: Tejun Heo <[email protected]>
Date: Mon, 14 May 2012 15:04:50 -0700
Subject: workqueue: skip nr_running sanity check in worker_enter_idle() if
trustee is active
From: Tejun Heo <[email protected]>
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 <[email protected]>
Reported-by: "Paul E. McKenney" <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/workqueue.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1214,8 +1214,13 @@ static void worker_enter_idle(struct wor
} 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)));
}
Patches currently in stable-queue which might be from [email protected] are
queue-3.0/workqueue-skip-nr_running-sanity-check-in-worker_enter_idle-if-trustee-is-active.patch
queue-3.0/block-fix-buffer-overflow-when-printing-partition-uuids.patch
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