[PATCH] workqueue: fix spurious CPU locality WARN fromprocess_one_work()

From: Tejun Heo
Date: Sun Jul 22 2012 - 12:44:19 EST

25511a4776 "workqueue: reimplement CPU online rebinding to handle idle
workers" added CPU locality sanity check in process_one_work(). It
triggers if a worker is executing on a different CPU without UNBOUND
or REBIND set.

This works for all normal workers but rescuers can trigger this
spuriously when they're serving the unbound or a disassociated
global_cwq - rescuers don't have either flag set and thus its
gcwq->cpu can be a different value including %WORK_CPU_UNBOUND.

Fix it by additionally testing %GCWQ_DISASSOCIATED.

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Reported-by: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
LKML-Refence: <20120721213656.GA7783@xxxxxxxxxxxxxxxxxx>
This should fix it. Will queue it on wq/for-3.6.


kernel/workqueue.c | 6 ++++++
1 file changed, 6 insertions(+)

--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1949,7 +1949,13 @@ __acquires(&gcwq->lock)

lockdep_copy_map(&lockdep_map, &work->lockdep_map);
+ /*
+ * Ensure we're on the correct CPU. DISASSOCIATED test is
+ * necessary to avoid spurious warnings from rescuers servicing the
+ * unbound or a disassociated gcwq.
+ */
+ !(gcwq->flags & GCWQ_DISASSOCIATED) &&
raw_smp_processor_id() != gcwq->cpu);

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