From: Andrew Morton <akpm@osdl•org>
To: Olaf Hering <olh@suse•de>
Cc: linuxppc-dev@ozlabs•org, reiserfs-dev@namesys•com,
reiser@namesys•com, jeffm@suse•de
Subject: Re: [PATCH] make gcc -O1 in fs/reiserfs optional
Date: Thu, 13 Oct 2005 16:27:34 -0700 [thread overview]
Message-ID: <20051013162734.615bba34.akpm@osdl.org> (raw)
In-Reply-To: <20051011190133.GA31348@suse.de>
Olaf Hering <olh@suse•de> wrote:
>
> On Wed, Apr 27, Hans Reiser wrote:
>
> > Olaf Hering wrote:
> >
> > >Jeff,
> > >
> > >you added this EXTRA_CFLAGS= during 2.4 development, I think the broken
> > >compiler was gcc 3.2 on SLES8. Can we turn this -O1 into a .config
> > >option?
>
> > Sounds reasonable.
>
> only compile with -O1 if the (very old) compiler is broken
> We use reiserfs alot in SLES9 on ppc64, and it was never seen
> with gcc33.
>
I dunno about this.
>
> Index: linux-2.6.12-rc3-olh/fs/reiserfs/Makefile
> ===================================================================
> --- linux-2.6.12-rc3-olh.orig/fs/reiserfs/Makefile
> +++ linux-2.6.12-rc3-olh/fs/reiserfs/Makefile
> @@ -21,13 +21,7 @@ ifeq ($(CONFIG_REISERFS_FS_POSIX_ACL),y)
> reiserfs-objs += xattr_acl.o
> endif
>
> -# gcc -O2 (the kernel default) is overaggressive on ppc32 when many inline
> -# functions are used. This causes the compiler to advance the stack
> -# pointer out of the available stack space, corrupting kernel space,
> -# and causing a panic. Since this behavior only affects ppc32, this ifeq
> -# will work around it. If any other architecture displays this behavior,
> -# add it here.
> -ifeq ($(CONFIG_PPC32),y)
> +ifeq ($(CONFIG_REISERFS_CC_REDUCE_OPTIMZE),y)
> EXTRA_CFLAGS := -O1
> endif
>
> Index: linux-2.6.12-rc3-olh/fs/Kconfig
> ===================================================================
> --- linux-2.6.12-rc3-olh.orig/fs/Kconfig
> +++ linux-2.6.12-rc3-olh/fs/Kconfig
> @@ -186,6 +186,18 @@ config REISERFS_FS
> If you like it, you can pay us to add new features to it that you
> need, buy a support contract, or pay us to port it to another OS.
>
> +config REISERFS_CC_REDUCE_OPTIMZE
> + bool "Reduce CC optimization level to workaround compiler bugs"
> + depends on PPC32
> + default n
> + help
> + gcc -O2 (the kernel default) is overaggressive on ppc32 when many inline
> + functions are used. This causes the compiler to advance the stack
> + pointer out of the available stack space, corrupting kernel space,
> + and causing a panic. Since this behavior only affects ppc32, this ifeq
> + will work around it. If any other architecture displays this behavior,
> + add it here.
> +
Are you sure it's due to inline functions? I thought the problem was that
certain versions of gcc did automatic inlining of non-inlined functions and
we get excessive stack windup due to that. And iirc we put in global
compiler options to defeat that behaviour. Andi would recall.
Furthermore, we do have infrastructure for detecting the gcc version at
build time. It would be better to use that for disabling `-O2', rather
than a config option.
next prev parent reply other threads:[~2005-10-13 23:31 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-04-26 21:10 [PATCH] make gcc -O1 in fs/reiserfs optional Olaf Hering
2005-04-26 21:46 ` Jeff Mahoney
2005-04-27 13:40 ` Hans Reiser
2005-10-11 19:01 ` Olaf Hering
2005-10-11 20:04 ` Hans Reiser
2005-10-13 23:27 ` Andrew Morton [this message]
2005-10-14 1:17 ` Jeff Mahoney
2006-07-24 6:52 ` [PATCH] use gcc -O1 in fs/reiserfs only for ancient gcc versions Olaf Hering
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20051013162734.615bba34.akpm@osdl.org \
--to=akpm@osdl$(echo .)org \
--cc=jeffm@suse$(echo .)de \
--cc=linuxppc-dev@ozlabs$(echo .)org \
--cc=olh@suse$(echo .)de \
--cc=reiser@namesys$(echo .)com \
--cc=reiserfs-dev@namesys$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox