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Message-ID: <c62985530812121725m19b779d8o2c274efecdca93ab@mail.gmail.com>
Date: Sat, 13 Dec 2008 02:25:16 +0100
From: "=?ISO-8859-1?Q?Fr=E9d=E9ric_Weisbecker?=" <fweisbec@gmail.com>
To: "Arnaldo Carvalho de Melo" <acme@redhat.com>,
       "Steven Rostedt" <srostedt@redhat.com>,
       "Vladislav Bolkhovitin" <vst@vlnb.net>,
       "Sam Ravnborg" <sam@ravnborg.org>, linux-scsi@vger.kernel.org,
       "James Bottomley" <James.Bottomley@hansenpartnership.com>,
       "Andrew Morton" <akpm@linux-foundation.org>,
       "FUJITA Tomonori" <fujita.tomonori@lab.ntt.co.jp>,
       "Mike Christie" <michaelc@cs.wisc.edu>, "Jeff Garzik" <jeff@garzik.org>,
       "Boaz Harrosh" <bharrosh@panasas.com>,
       "Linus Torvalds" <torvalds@linux-foundation.org>,
       linux-kernel@vger.kernel.org, scst-devel@lists.sourceforge.net,
       "Bart Van Assche" <bart.vanassche@gmail.com>,
       "Nicholas A. Bellinger" <nab@linux-iscsi.org>,
       fweisbec <fweisbec@gmail.com>, "Ingo Molnar" <mingo@elte.hu>
Subject: Re: [PATCH][RFC 2/23]: SCST core
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2008/12/13 Arnaldo Carvalho de Melo <acme@redhat.com>:
> Steven, is it possible to trigger tracing for any function when a
> function in the list set up by the user is running and then stop tracing
> when it exits?
>
> - Arnaldo
>

Hi Arnaldo,

Yes it's possible with ftrace, by using the function graph tracer ( an
ftrace extension that adds the tracing on return).

To enable it just do:
echo function_graph > /debugfs/tracing/current_tracer

And to trace by choosing a particular function as the root of the call
stack, just do the things
 explained on this patch:
http://git.kernel.org/?p=linux/kernel/git/mingo/linux-2.6-sched-devel.git;a=commit;h=ea4e2bc4d9f7370e57a343ccb5e7c0ad3222ec3c

And the tracing will finish after this function returns :-)
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