linux-kernel - Re: [PATCH] tracing: Add task activate/deactivate tracepoints

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Message-ID: <20100531165135.GD5157@nowhere>
Date:	Mon, 31 May 2010 18:51:37 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] tracing: Add task activate/deactivate tracepoints

On Mon, May 31, 2010 at 06:18:35PM +0200, Peter Zijlstra wrote:
> On Mon, 2010-05-31 at 16:48 +0200, Frederic Weisbecker wrote:
> > > Should we maybe cure this and rely on sched_switch() to detect sleeps?
> > > It seems natural since only the current task can go to sleep, its just
> > > that the whole preempt state gets a bit iffy.
> 
> How about something like the below?
> 
> Steve, is that proper usage of CREATE_TRACE_POINT?
> 
> ---
> Subject: sched, trace: Fix sched_switch() prev_state argument
> From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Date: Mon May 31 18:13:25 CEST 2010
> 
> For CONFIG_PREEMPT=y kernels the sched_switch(.prev_state) argument
> isn't useful because we can get preempted with current->state !=
> TASK_RUNNING without actually getting removed from the runqueue.
> 
> Cure this by treating all preempted tasks as runnable from the
> tracer's point of view.
> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> ---



Other than Steve's said, the thing looks good.

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