From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
linux-rt-users <linux-rt-users@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Clark Williams <williams@redhat.com>,
"Luis Claudio R. Goncalves" <lclaudio@uudg.org>,
John Kacur <jkacur@redhat.com>,
Ulrich Obergfell <uobergfe@redhat.com>
Subject: Re: [PATCH RT] rt: Make cpu_chill() use hrtimer instead of msleep()
Date: Fri, 07 Feb 2014 15:21:46 +0100 [thread overview]
Message-ID: <52F4EBFA.3040401@linutronix.de> (raw)
In-Reply-To: <20140207091313.097f9059@gandalf.local.home>
On 02/07/2014 03:13 PM, Steven Rostedt wrote:
> On Fri, 7 Feb 2014 09:08:34 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
>
>>> could you please tell me which two locks are invovled here?
>
> I should have also stated that it was only one lock that was involved.
> But the lock owner was doing a msleep() that requires a wakeup by
> ksoftirqd to continue. If ksoftirqd happens to be blocked on a lock
> held by the msleep() caller, then you have your deadlock.
That makes sense.
> It's best not to have any softirqs going to sleep requiring another
> softirq to wake it up. Note, if we ever require a timer softirq to do a
> cpu_chill() it will most definitely hit this deadlock.
Yes. And that sleep in softirq is also not really nice but this isn't
new. Thanks for the patch & explanation.
>
> -- Steve
Sebastian
next prev parent reply other threads:[~2014-02-07 14:21 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-05 16:51 [PATCH RT] rt: Make cpu_chill() use hrtimer instead of msleep() Steven Rostedt
2014-02-05 16:57 ` Steven Rostedt
2014-02-07 11:30 ` Sebastian Andrzej Siewior
2014-02-07 14:08 ` Steven Rostedt
2014-02-07 14:13 ` Steven Rostedt
2014-02-07 14:21 ` Sebastian Andrzej Siewior [this message]
2014-02-19 11:53 ` [PATCH RT] kernel/hrtimer: be non-freezeable in cpu_chill() Sebastian Andrzej Siewior
2014-02-19 15:27 ` Steven Rostedt
2014-02-19 15:42 ` Sebastian Andrzej Siewior
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