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Date: Wed, 4 Feb 2009 18:36:43 +0300
From: Anton Vorontsov <avorontsov@ru.mvista.com>
To: =?utf8?B?RnLDqWTDqXJpYw==?= Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <srostedt@redhat.com>, Ingo Molnar <mingo@elte.hu>,
       Paul Mackerras <paulus@samba.org>,
       Benjamin Herrenschmidt <benh@kernel.crashing.org>,
       linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org,
       linux-rt-users@vger.kernel.org
Subject: Re: [PATCH 3/3] tracing: Tracers that use CALLER_ADDR macros
	should select FRAME_POINTER
Message-ID: <20090204153643.GA16681@oksana.dev.rtsoft.ru>
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On Wed, Feb 04, 2009 at 04:26:15PM +0100, Frédéric Weisbecker wrote:
[...]
> > @@ -136,6 +138,7 @@ config SCHED_TRACER
> >        select TRACING
> >        select CONTEXT_SWITCH_TRACER
> >        select TRACER_MAX_TRACE
> > +       select FRAME_POINTER
> >        help
> >          This tracer tracks the latency of the highest priority task
> >          to be scheduled in, starting from the point it has woken up.
> > --
> 
> 
> Looks right.
> 
> BTW, how behaves builtin_return_address in case of !FRAME_POINTERS ?
> I guess it would only work with the first caller builtin_return_address(0)

It depends on the architecture. On PowerPC we always have frame pointers,
thus __builtin_return_address(1..) will always work. On x86 it won't work
that way.

Thanks,

-- 
Anton Vorontsov
email: cbouatmailru@gmail.com
irc://irc.freenode.net/bd2