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

From: Ingo Molnar <[email-masked]>
Date: Fri, 26 Dec 2008 16:33:18 +0100

* 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

------------->
>>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