From: Steven Rostedt In -rt, most spin_locks() turn into mutexes. One of these spin_lock conversions is performed on the workqueue gcwq->lock. When the idle worker is worken, the first thing it will do is grab that same lock and it too will block, possibly jumping into the same code, but because nr_running would already be decremented it prevents an infinite loop. But this is still a waste of CPU cycles, and it doesn't follow the method of mainline, as new workers should only be woken when a worker thread is truly going to sleep, and not just blocked on a spin_lock(). Check the saved_state too before waking up new workers. Cc: stable-rt@vger.kernel.org Signed-off-by: Steven Rostedt Signed-off-by: Sebastian Andrzej Siewior --- kernel/sched/core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 5051ca6..781e6c4 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3632,8 +3632,10 @@ need_resched: * If a worker went to sleep, notify and ask workqueue * whether it wants to wake up a task to maintain * concurrency. + * Only call wake up if prev isn't blocked on a sleeping + * spin lock. */ - if (prev->flags & PF_WQ_WORKER) { + if (prev->flags & PF_WQ_WORKER && !prev->saved_state) { struct task_struct *to_wakeup; to_wakeup = wq_worker_sleeping(prev, cpu); -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/