From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/6 v2] sched: Init idle->on_rq in init_idle()
Date: Tue, 11 Feb 2014 16:51:15 +0100 [thread overview]
Message-ID: <20140211155115.GR27965@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <alpine.DEB.2.02.1402111534000.21991@ionos.tec.linutronix.de>
On Tue, Feb 11, 2014 at 04:34:38PM +0100, Thomas Gleixner wrote:
> I could slap myself for not writing a proper changelog right away. It
> took me some time to figure out why it was added in the first place,
> why it's not longer necessary and why I kept it.
:-)
Thanks!
---
Subject: sched: Init idle->on_rq in init_idle()
From: Thomas Gleixner <tglx@linutronix.de>
Date: Fri, 7 Feb 2014 20:58:37 +0100
We stumbled in RT over a SMP bringup issue on ARM where the
idle->on_rq == 0 was causing try_to_wakeup() on the other cpu to run
into nada land.
After adding that idle->on_rq = 1; I was able to find the root cause
of the lockup: the idle task on the newly woken up cpu was fiddling
with a sleeping spinlock, which is a nono.
I kept the init of idle->on_rq to keep the state consistent and to
avoid another long lasting debug session.
As a side note, the whole debug mess could have been avoided if
might_sleep() would have yelled when called from the idle task. That's
fixed with patch 2/6 - and that one actually has a changelog :)
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1391803122-4425-2-git-send-email-bigeasy@linutronix.de
---
kernel/sched/core.c | 1 +
1 file changed, 1 insertion(+)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4443,6 +4443,7 @@ void init_idle(struct task_struct *idle,
rcu_read_unlock();
rq->curr = rq->idle = idle;
+ idle->on_rq = 1;
#if defined(CONFIG_SMP)
idle->on_cpu = 1;
#endif
next prev parent reply other threads:[~2014-02-11 15:51 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-07 19:58 A pile of sched patches Sebastian Andrzej Siewior
2014-02-07 19:58 ` [PATCH 1/6] sched: Init idle->on_rq in init_idle() Sebastian Andrzej Siewior
2014-02-07 21:09 ` Peter Zijlstra
2014-02-11 9:17 ` [PATCH 1/6 v2] " Sebastian Andrzej Siewior
2014-02-11 9:21 ` Peter Zijlstra
2014-02-11 15:34 ` Thomas Gleixner
2014-02-11 15:51 ` Peter Zijlstra [this message]
2014-02-21 21:31 ` [tip:sched/core] " tip-bot for Thomas Gleixner
2014-02-22 18:01 ` tip-bot for Thomas Gleixner
2014-02-07 19:58 ` [PATCH 2/6] sched: Check for idle task in might_sleep() Sebastian Andrzej Siewior
2014-02-21 21:31 ` [tip:sched/core] " tip-bot for Thomas Gleixner
2014-02-22 18:02 ` tip-bot for Thomas Gleixner
2014-02-07 19:58 ` [PATCH 3/6] sched: Better debug output for might sleep Sebastian Andrzej Siewior
2014-02-21 21:31 ` [tip:sched/core] " tip-bot for Thomas Gleixner
2014-02-22 18:02 ` [tip:sched/core] sched: Add better debug output for might_sleep() tip-bot for Thomas Gleixner
2014-02-07 19:58 ` [PATCH 4/6] sched: Adjust sched_reset_on_fork when nothing else changes Sebastian Andrzej Siewior
2014-02-21 21:32 ` [tip:sched/core] " tip-bot for Thomas Gleixner
2014-02-22 18:02 ` [tip:sched/core] sched: Adjust p-> " tip-bot for Thomas Gleixner
2014-02-07 19:58 ` [PATCH 5/6] sched: Queue RT tasks to head when prio drops Sebastian Andrzej Siewior
2014-02-21 21:32 ` [tip:sched/core] " tip-bot for Thomas Gleixner
2014-02-22 18:02 ` tip-bot for Thomas Gleixner
2014-02-07 19:58 ` [PATCH 6/6] sched: Consider pi boosting in setscheduler Sebastian Andrzej Siewior
2014-02-21 21:32 ` [tip:sched/core] " tip-bot for Thomas Gleixner
2014-02-22 18:02 ` [tip:sched/core] sched: Consider pi boosting in setscheduler() tip-bot for Thomas Gleixner
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