From: Steven Rostedt <rostedt@xxxxxxxxxxx> 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@xxxxxxxxxxxxxxx Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> --- kernel/sched.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/sched.c b/kernel/sched.c index 96dd9c2..59bb8bc 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -4436,8 +4436,10 @@ static inline void sched_submit_work(struct task_struct *tsk) /* * 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 (tsk->flags & PF_WQ_WORKER) + if (tsk->flags & PF_WQ_WORKER && !tsk->saved_state) wq_worker_sleeping(tsk); /* -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe stable-rt" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
