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Date: Mon, 23 Mar 2009 20:33:46 +0100
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org,
       tglx@linutronix.de, mingo@elte.hu, linux-tip-commits@vger.kernel.org
Subject: Re: [tip:tracing/filters] tracing/events: don't use wake up for
	events
Message-ID: <20090323193345.GD5988@nowhere>
References: <1237759847-21025-4-git-send-email-fweisbec@gmail.com> <tip-07edf7121374609709ef1b0889f6e7b8d6a62ec1@git.kernel.org> <alpine.DEB.2.00.0903231520330.3578@gandalf.stny.rr.com>
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On Mon, Mar 23, 2009 at 03:21:55PM -0400, Steven Rostedt wrote:
> 
> 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


Indeed.

I scratched my head the evening long to find a name that could mean:
trace_current_buffer_unlock_commit_nowake()  ;-)

I think my headache brought me to this silly trace_nowake....

I will fix the name.
Thanks.

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