linux-kernel - Re: [PATCH v2 2/4] ftrace: introduce workqueue_handler_exit tracepoint and rename workqueue_execution to workqueue_handler

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Message-ID: <20090415120527.GA6960@redhat.com>
Date:	Wed, 15 Apr 2009 14:05:27 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Zhaolei <zhaolei@...fujitsu.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Tom Zanussi <tzanussi@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] ftrace: introduce workqueue_handler_exit
	tracepoint and rename workqueue_execution to workqueue_handler_entry

On 04/15, Ingo Molnar wrote:
>
> The patches try to map and instrument the life cycle of a worklet,
> and the main actions that occur in the workqueue subsystem in
> general.
>
> The purpose is instrumentation: for debugging purposes, for
> improving kernel code and for just understanding how the system
> functions and what its dynamic actions are.
>
> In that sense the worklet 'key' possibly getting reallocated and
> reused before the 'completed' action was traced is probably not a
> big deal - but tools have to be aware of it possibly happening (and
> most not hard-code any assumption to the contrary).
>
> Plus the exit handler must not dereference the worklet either.
> Safest would be to make this sure in the prototype already: pass in
> a void * key, not a work structure.

Yes, I think you are right.

And thanks for your explanations!

Oleg.

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