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, 7 Feb 2014 12:30:06 +0100 [thread overview]
Message-ID: <20140207113006.GD23668@linutronix.de> (raw)
In-Reply-To: <20140205115125.3cc950ce@gandalf.local.home>
* Steven Rostedt | 2014-02-05 11:51:25 [-0500]:
>Ulrich Obergfell pointed out that cpu_chill() calls msleep() which is woken
>up by the ksoftirqd running the TIMER softirq. But as the cpu_chill() is
>called from softirq context, it may block the ksoftirqd() from running, in
>which case, it may never wake up the msleep() causing the deadlock.
>
>I checked the vmcore, and irq/74-qla2xxx is stuck in the msleep() call,
>running on CPU 8. The one ksoftirqd that is stuck, happens to be the one that
>runs on CPU 8, and it is blocked on a lock held by irq/74-qla2xxx. As that
>ksoftirqd is the one that will wake up irq/74-qla2xxx, and it happens to be
>blocked on a lock that irq/74-qla2xxx holds, we have our deadlock.
could you please tell me which two locks are invovled here?
Sebastian
next prev parent reply other threads:[~2014-02-07 11:30 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 [this message]
2014-02-07 14:08 ` Steven Rostedt
2014-02-07 14:13 ` Steven Rostedt
2014-02-07 14:21 ` Sebastian Andrzej Siewior
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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