Subject: Re: [BUG] next-20081216 - WARNING: at kernel/smp.c:333 smp_call_function_mask

From: Kamalesh Babulal <[email-masked]>
Date: Fri, 26 Dec 2008 22:34:52 +0530

* Ingo Molnar <[email-masked]> [2008-12-26 16:33:18]:

> 
> * Kamalesh Babulal <[email-masked]> wrote:
> 
> > * Sam Ravnborg <[email-masked]> [2008-12-26 11:27:16]:
> > 
> > > On Fri, Dec 26, 2008 at 02:05:47AM -0800, Yinghai Lu wrote:
> > > > Kamalesh Babulal wrote:
> > > > > * Yinghai Lu <[email-masked]> [2008-12-24 12:34:41]:
> > > > > 
> > > > >> --
> > > > > 
> > > > > After the applying the patch, the kernel panic's with the same backtrace. The
> > > > > box is running Fedora 5 on it.
> > > > > 
> > > > 
> > > > please try...
> > > > Ingo, do we need to switch to use #idef and inline function instead?
> > > 
> > > I recall David Howells had a similar issue with the bootparamter patch set.
> > > The workaround he used was to add a barrier(); call in the weak function
> > > to avoid the inline.
> > > 
> > > [full context kept as I added David to to: list].
> > > 	Sam
> > > 
> > 
> > Hi Yinghai,
> > 
> > 	Thanks, after applying the patch, the kernel boot's up fine.
> 
> how about the patch below, does that work too? (after removing Yinghai's 
> patch)
> 
> 	Ingo

Hi Ingo,

	Kernel crashes with the same trace, after the applying the patch.

> 
> ------------->
> From 0d41e654c877a0de441448ca2f63a72ed11c5d84 Mon Sep 17 00:00:00 2001
> From: Ingo Molnar <[email-masked]>
> Date: Fri, 26 Dec 2008 14:39:51 +0100
> Subject: [PATCH] kbuild, sparseirq: work around GCC bug with __weak aliases
> 
> Impact: fix panic on null pointer with sparseirq
> 
> Certain versions of GCC inline the weak global functions.
> Work it around by marking __weak functions as noinline.
> 
> Signed-off-by: Ingo Molnar <[email-masked]>
> ---
>  include/linux/compiler-gcc.h |    8 +++++++-
>  1 files changed, 7 insertions(+), 1 deletions(-)
> 
> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
> index 5c8351b..1ad72e6 100644
> --- a/include/linux/compiler-gcc.h
> +++ b/include/linux/compiler-gcc.h
> @@ -41,11 +41,17 @@
> 
>  #define __deprecated			__attribute__((deprecated))
>  #define __packed			__attribute__((packed))
> -#define __weak				__attribute__((weak))
>  #define __naked				__attribute__((naked))
>  #define __noreturn			__attribute__((noreturn))
> 
>  /*
> + * Mark weak aliases also noinline, because some GCC versions
> + * incorrectly inline weak aliases (even when a non-weak variant
> + * is there) and thus cause crashes:
> + */
> +#define __weak				__attribute__((weak)) noinline
> +
> +/*
>   * From the GCC manual:
>   *
>   * Many functions have no effects except the return value and their
> --
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-- 
Thanks & Regards,
Kamalesh Babulal,
Linux Technology Center,
IBM, ISTL.