From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org,
linux-rt-users <linux-rt-users@vger.kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Carsten Emde <C.Emde@osadl.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
John Kacur <jkacur@redhat.com>, <stable-rt@vger.kernel.org>
Subject: [PATCH RT 01/16] sched/workqueue: Only wake up idle workers if not blocked on sleeping spin lock
Date: Mon, 09 Sep 2013 08:45:32 -0400 [thread overview]
Message-ID: <20130909124555.974389218@goodmis.org> (raw)
In-Reply-To: 20130909124531.445392664@goodmis.org
[-- Attachment #1: 0001-sched-workqueue-Only-wake-up-idle-workers-if-not-blo.patch --]
[-- Type: text/plain, Size: 1457 bytes --]
From: Steven Rostedt <rostedt@goodmis.org>
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 <rostedt@goodmis.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
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 751ec60..8674878 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3528,8 +3528,10 @@ 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
next prev parent reply other threads:[~2013-09-09 13:26 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-09 12:45 [PATCH RT 00/16] 3.4.57-rt73-rc1 stable review Steven Rostedt
2013-09-09 12:45 ` Steven Rostedt [this message]
2013-09-09 12:45 ` [PATCH RT 02/16] x86/mce: fix mce timer interval Steven Rostedt
2013-09-09 12:45 ` [PATCH RT 03/16] genirq: Set irq thread to RT priority on creation Steven Rostedt
2013-09-09 12:45 ` [PATCH RT 04/16] list_bl.h: make list head locking RT safe Steven Rostedt
2013-09-09 12:45 ` [PATCH RT 05/16] list_bl.h: fix it for for !SMP && !DEBUG_SPINLOCK Steven Rostedt
2013-09-09 12:45 ` [PATCH RT 06/16] timers: prepare for full preemption improve Steven Rostedt
2013-09-09 12:45 ` [PATCH RT 07/16] kernel/cpu: fix cpu down problem if kthreads cpu is going down Steven Rostedt
2013-09-09 12:45 ` [PATCH RT 08/16] kernel/hotplug: restore original cpu mask oncpu/down Steven Rostedt
2013-09-09 12:45 ` [PATCH RT 09/16] drm/i915: drop trace_i915_gem_ring_dispatch on rt Steven Rostedt
2013-09-09 12:45 ` [PATCH RT 10/16] rt,ntp: Move call to schedule_delayed_work() to helper thread Steven Rostedt
2013-09-09 12:45 ` [PATCH RT 11/16] hwlat-detector: Update hwlat_detector to add outer loop detection Steven Rostedt
2013-09-09 12:45 ` [PATCH RT 12/16] hwlat-detect/trace: Export trace_clock_local for hwlat-detector Steven Rostedt
2013-09-09 12:45 ` [PATCH RT 13/16] hwlat-detector: Use trace_clock_local if available Steven Rostedt
2013-09-09 12:45 ` [PATCH RT 14/16] hwlat-detector: Use thread instead of stop machine Steven Rostedt
2013-09-09 12:45 ` [PATCH RT 15/16] genirq: do not invoke the affinity callback via a workqueue Steven Rostedt
2013-09-09 12:45 ` [PATCH RT 16/16] Linux 3.4.57-rt73-rc1 Steven Rostedt
-- strict thread matches above, loose matches on Subject: below --
2013-09-09 12:47 [PATCH RT 00/16] 3.2.50-rt71-rc1 stable review Steven Rostedt
2013-09-09 12:47 ` [PATCH RT 01/16] sched/workqueue: Only wake up idle workers if not blocked on sleeping spin lock Steven Rostedt
2013-09-09 14:35 [PATCH RT 00/16] 3.0.89-rt118-rc1 stable review Steven Rostedt
2013-09-09 14:35 ` [PATCH RT 01/16] sched/workqueue: Only wake up idle workers if not blocked on sleeping spin lock Steven Rostedt
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