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

Ingo Molnar
2008-12-26T15:36:14Z

* Kamalesh Babulal <kamalesh@linux.vnet.ibm.com> wrote:

> * Sam Ravnborg <sam@ravnborg.org> [2008-12-26 11:27:16]:
>
> > On Fri, Dec 26, 2008 at 02:05:47AM -0800, Yinghai Lu wrote:
> > > Kamalesh Babulal wrote:
> > > > * Yinghai Lu <yinghai@kernel.org> [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 <mingo@elte.hu>
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 <mingo@elte.hu>
---
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