From mboxrd@z Thu Jan  1 00:00:00 1970
From: Benjamin Herrenschmidt <benh-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
Subject: Re: 2.6.27-rc4-git1: Reported regressions from 2.6.26
Date: Mon, 25 Aug 2008 10:48:21 +1000
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To: "Rafael J. Wysocki" <rjw-KKrjLPT3xs0@public.gmane.org>
Cc: Linux Kernel Mailing List <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Adrian Bunk <bunk-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Natalie Protasevich <protasnb-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Kernel Testers List <kernel-testers-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>


> Bug-Entry	: http://bugzilla.kernel.org/show_bug.cgi?id=11414
> Subject		: Random crashes with 2.6.27-rc3 on PPC
> Submitter	: Michael Buesch <mb-fseUSCV1ubazQB+pC5nmwQ@public.gmane.org>
> Date		: 2008-08-23 14:10 (1 days old)
> References	: http://marc.info/?l=linux-kernel&m=121950076812616&w=4

This appears to be a gcc bug when -fno-omit-stack-pointer is used (which
we mostly don't need on ppc anyway except that another gcc stupidity makes
it mandatory for -pg which ftrace needs).

We're working on a two fold workaround: removing -fno-omit-stack-pointer
in all the cases where we don't really need it, and for when we do (ie,
CONFIG_FTRACE becaues of -pg), using -mno-sched-epilog which seems to
work around it.

The root cause in gcc hasn't been fully identified yet.

Ben.