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

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Message-ID: <20090323193345.GD5988@nowhere>
Date:	Mon, 23 Mar 2009 20:33:46 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, mingo@...e.hu,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:tracing/filters] tracing/events: don't use wake up for
	events

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@...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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