Re: 2.6.27-rc4-git1: Reported regressions from 2.6.26

Benjamin Herrenschmidt
2008-08-25T00:48:21Z

> 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.