Messages in this thread Patch in this message | | | From | Joe Lawrence <> | Subject | [PATCH] workqueue: add quiescent state between work items | Date | Sun, 5 Oct 2014 00:56:40 -0400 |
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Similar to the stop_machine deadlock scenario on !PREEMPT kernels addressed in b22ce2785d97 "workqueue: cond_resched() after processing each work item", kworker threads requeueing back-to-back with zero jiffy delay can stall RCU. The cond_resched call introduced in that fix will yield only iff there are other higher priority tasks to run, so force a quiescent RCU state between work items with cond_resched_rcu_qs.
Signed-off-by: Joe Lawrence <joe.lawrence@stratus.com> Link: https://lkml.kernel.org/r/20140926105227.01325697@jlaw-desktop.mno.stratus.com Link: https://lkml.kernel.org/r/20140929115445.40221d8e@jlaw-desktop.mno.stratus.com --- kernel/workqueue.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 5dbe22a..09b685d 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -2043,9 +2043,10 @@ __acquires(&pool->lock) * kernels, where a requeueing work item waiting for something to * happen could deadlock with stop_machine as such work item could * indefinitely requeue itself while all other CPUs are trapped in - * stop_machine. + * stop_machine. At the same time, report a quiescent RCU state so + * the same condition doesn't freeze RCU. */ - cond_resched(); + cond_resched_rcu_qs(); spin_lock_irq(&pool->lock); -- 1.7.10.4
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