From 544ecf310f0e7f51fa057ac2a295fc1b3b35a9d3 Mon Sep 17 00:00:00 2001 From: Tejun Heo <tj@kernel.org> Date: Mon, 14 May 2012 15:04:50 -0700 Subject: [PATCH] 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 --- kernel/workqueue.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 211eadb23323..c36c86cf7900 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1213,8 +1213,13 @@ 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))); } -- 2.34.1