tree 417e606b3a1a7eaa31a3847a5101db37041e0c20
parent 0976dfc1d0cd80a4e9dfaf87bd8744612bde475a
author Tejun Heo <tj@kernel.org> 1337033090 -0700
committer Tejun Heo <tj@kernel.org> 1337033090 -0700

workqueue: skip nr_running sanity check in worker_enter_idle() if trustee is active

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>
Cc: stable@vger.kernel.org