[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-ID: <20090320164404.GA19933@oksana.dev.rtsoft.ru>
Date: Fri, 20 Mar 2009 19:44:04 +0300
From: Anton Vorontsov <avorontsov@...mvista.com>
To: Ingo Molnar <mingo@...e.hu>
Cc: Steven Rostedt <srostedt@...hat.com>,
Sam Ravnborg <sam@...nborg.org>,
Paul Mackerras <paulus@...ba.org>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 0/3] Tracers vs. CALLER_ADDR on PowerPC
Hi all,
Here is another approach to fixing tracers vs. CALLER_ADDR problem
on PowerPC.
Preface for those who don't know or forgot what the problem is:
Gcc frame pointers do nothing useful on PowerPC (they're harmful,
actually), and thus lib/Kconfig.debug makes CONFIG_FRAME_POINTER
unselectable on PPC targets, but CALLER_ADDR macros are available
only with CONFIG_FRAME_POINTER, therefore tracing is completely
useless on PowerPC:
[...]
<idle>-0 0X.h3 2us+: 0:140:R + [000] 1733:120:S mvtsd
<idle>-0 0X.h3 9us+: 0 (0)
<idle>-0 0X..3 72us : 0 (0)
<idle>-0 0X..3 73us : 0:140:R ==> [000] 1733:120:R mvtsd
While it should look like this:
[...]
<idle>-0 0X.h3 2us+: 0:140:R + [000] 1740:120:S mvtsd
<idle>-0 0X.h3 9us+: hrtimer_wakeup (__run_hrtimer)
<idle>-0 0X..3 87us : cpu_idle (__got2_end)
<idle>-0 0X..3 89us : 0:140:R ==> [000] 1740:120:R mvtsd
I've tried to fix the issue via expanding the #ifdef in the ftrace.h:
http://lkml.org/lkml/2009/1/31/141
Then Steven Rostedt suggested to implement something more generic,
i.e. HAVE_NORMAL_FRAME_POINTERS Kconfig symbol.
I found a way to solve the problem w/o additional symbols, but
with some Makefile magic (http://lkml.org/lkml/2009/2/4/273).
But because of top-level Makefile issues on other arches
(http://lkml.org/lkml/2009/2/14/89) I had to abandon the approach.
So, this patch set combines Steven Rostedt's idea and a small
Makefile change, so that now only top-level Makefile has to know
about the new symbol, and the rest of the kernel can stay with
using CONFIG_FRAME_POINTER.
--
Anton Vorontsov
email: cbouatmailru@...il.com
irc://irc.freenode.net/bd2
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists