linux-kernel - Re: [tip:tracing/filters] tracing/events: don't use wake up for events

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Message-ID: <alpine.DEB.2.00.0903231520330.3578@gandalf.stny.rr.com>
Date:	Mon, 23 Mar 2009 15:21:55 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	fweisbec@...il.com, tglx@...utronix.de, mingo@...e.hu
cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:tracing/filters] tracing/events: don't use wake up for
 events


On Mon, 23 Mar 2009, Frederic Weisbecker wrote:
> tracing/events: don't use wake up for events
> 
> Impact: fix hard-lockup with sched switch events
> 
> Some ftrace events, such as sched wakeup, can be traced
> while the runqueue lock is hold. Since they are using
> trace_current_buffer_unlock_commit(), they call wake_up()
> which can try to grab the runqueue lock too, resulting in
> a deadlock.
> 
> Now for all event, we call a new helper:
> trace_nowake_buffer_unlock_commit() which do pretty the same than

Ug, that's an ugly name. It should at least be:

  trace_buffer_unlock_commit_nowake

to be more in line with kernel conventions. That is where the derivitive
has the same name as the original, like preempt_enable_noresched.

-- Steve

> trace_current_buffer_unlock_commit() except than it doesn't call
> trace_wake_up().
> 
> Reported-by: Ingo Molnar <mingo@...e.hu>
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> LKML-Reference: <1237759847-21025-4-git-send-email-fweisbec@...il.com>
> Signed-off-by: Ingo Molnar <mingo@...e.hu>
> 
> 
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