4.14.63-rt41-rc2 stable review patch. If anyone has any objections, please let me know.
------------------ From: Daniel Bristot de Oliveira <[email protected]> [ Upstream commit 2bb94c48b2ffaabf8c15a51e5cc1b4c541988cab ] If a worker invokes schedule() then we may have the call chain: schedule() -> sched_submit_work() -> wq_worker_sleeping() -> wake_up_worker() -> wake_up_process(). The last wakeup may cause a schedule which is unnecessary because we are already in schedule() and do it anyway. Add a preempt_disable() + preempt_enable_no_resched() around wq_worker_sleeping() so the context switch could be delayed until __schedule(). Signed-off-by: Daniel Bristot de Oliveira <[email protected]> Cc: Clark Williams <[email protected]> Cc: Tommaso Cucinotta <[email protected]> Cc: Romulo da Silva de Oliveira <[email protected]> Cc: Sebastian Andrzej Siewior <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Peter Zijlstra <[email protected]> Signed-off-by: Steven Rostedt (VMware) <[email protected]> [bigeasy: rewrite changelog] Signed-off-by: Sebastian Andrzej Siewior <[email protected]> --- kernel/sched/core.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index fa5b76255f8c..a5ce37b90fca 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3482,10 +3482,15 @@ 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. + * As this function is called inside the schedule() context, + * we disable preemption to avoid it calling schedule() again + * in the possible wakeup of a kworker. */ - if (tsk->flags & PF_WQ_WORKER) + if (tsk->flags & PF_WQ_WORKER) { + preempt_disable(); wq_worker_sleeping(tsk); - + preempt_enable_no_resched(); + } if (tsk_is_pi_blocked(tsk)) return; -- 2.18.0
