46 lines
1.8 KiB
Diff
46 lines
1.8 KiB
Diff
From 1241476225268360ae571ec5de750f504cac3604 Mon Sep 17 00:00:00 2001
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From: Steven Rostedt <rostedt@goodmis.org>
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Date: Mon, 18 Mar 2013 15:12:49 -0400
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Subject: [PATCH 114/269] sched/workqueue: Only wake up idle workers if not
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blocked on sleeping spin lock
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.37-rt20.tar.xz
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In -rt, most spin_locks() turn into mutexes. One of these spin_lock
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conversions is performed on the workqueue gcwq->lock. When the idle
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worker is worken, the first thing it will do is grab that same lock and
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it too will block, possibly jumping into the same code, but because
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nr_running would already be decremented it prevents an infinite loop.
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But this is still a waste of CPU cycles, and it doesn't follow the method
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of mainline, as new workers should only be woken when a worker thread is
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truly going to sleep, and not just blocked on a spin_lock().
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Check the saved_state too before waking up new workers.
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Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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kernel/sched/core.c | 4 +++-
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1 file changed, 3 insertions(+), 1 deletion(-)
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diff --git a/kernel/sched/core.c b/kernel/sched/core.c
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index 8033a8f4efdd..acca3e94ee27 100644
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--- a/kernel/sched/core.c
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+++ b/kernel/sched/core.c
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@@ -3498,8 +3498,10 @@ static void __sched notrace __schedule(bool preempt)
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* If a worker went to sleep, notify and ask workqueue
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* whether it wants to wake up a task to maintain
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* concurrency.
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+ * Only call wake up if prev isn't blocked on a sleeping
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+ * spin lock.
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*/
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- if (prev->flags & PF_WQ_WORKER) {
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+ if (prev->flags & PF_WQ_WORKER && !prev->saved_state) {
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struct task_struct *to_wakeup;
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to_wakeup = wq_worker_sleeping(prev);
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--
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2.20.1
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