Re: Random crashes with 2.6.27-rc3 on PPC

From: Michael Buesch
Date: Sun Aug 24 2008 - 11:01:09 EST


On Sunday 24 August 2008 16:46:38 Andreas Schwab wrote:
> Michael Buesch <mb@xxxxxxxxx> writes:
>
> > The following workaround seems to fix the crashes on powerpc.
> > However, this patch is clearly not what we want for other architectures,
> > as they might need -fno-omit-frame-pointer to function properly.
>
> This has a better chance to be accepted. :-)
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 8b5a7d3..f9a2e48 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -394,7 +394,7 @@ config LOCKDEP
> bool
> depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
> select STACKTRACE
> - select FRAME_POINTER if !X86 && !MIPS
> + select FRAME_POINTER if !X86 && !MIPS && !PPC
> select KALLSYMS
> select KALLSYMS_ALL

This is not what my patch is doing.
Your patch always forces FRAME_POINTER off. At least as far as lockdep is concerned.
What about other parts of the kernel that enable FRAME_POINTER?

I think this should be fixed in the makefile by substitution of
-fno-omit-frame-pointer on PPC (and probably depending on the compiler
version).

Otherwise, if somebody else decides to do select FRAME_POINTER in some other
code, the bug will reappear.
I'm also not sure if it's desired to always force FRAME_POINTER off.

--
Greetings Michael.
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