linux-kernel - Re: Section mismatch: kernel/workqueue.c

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Date:	Mon, 4 Feb 2008 06:55:40 +0100
From:	Sam Ravnborg <sam@...nborg.org>
To:	Peter Teoh <htmldeveloper@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Section mismatch: kernel/workqueue.c

On Mon, Feb 04, 2008 at 10:57:18AM +0800, Peter Teoh wrote:
> During compilation of the linus tree the following warnings are encountered:
> 
> WARNING: kernel/built-in.o(.data+0x2480): Section mismatch in
> reference from the variable workqueue_cpu_callback_nb.14223 to the
> function .devinit.text:workqueue_cpu_callback()
> The variable workqueue_cpu_callback_nb.14223 references
> the function __devinit workqueue_cpu_callback()
> If the reference is valid then annotate the
> variable with __init* (see linux/init.h) or name the variable:
> *driver, *_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console,
> 
> This fix is to correct the following warning during compilation.
> Based on my "elementary" analysis, as it is called from other
> non-__init functions, this function cannot be declared as __devinit(),
> correct?   Please comment.   Thanks :-).
> 
> Signed-off-by: Peter Teoh <htmldeveloper@...il.com>

Hi Peter.
I changed this and the following warning from relay using following
patch.

	Sam


>From 5fc28317ea634483360c43b015f230c68ad2c0f4 Mon Sep 17 00:00:00 2001
From: Sam Ravnborg <sam@...nborg.org>
Date: Thu, 31 Jan 2008 21:16:16 +0100
Subject: [PATCH] cpu: silence section mismatch warnings for hotcpu notifies

The hotcpu_notifier is used to create notifiers to be called later.
It really looks like the functions that are registered are only
relevant in a HOTPLUG_CPU configuration and the correct fix was
to wrap them in an #ifdef / #endif or similar.
But for now just tell modpost to silence the warning by annotating
the static variable with __refdata.

This silences the following warnings in kernel/:
WARNING: o-x86_64/kernel/built-in.o(.data+0x960): Section mismatch in reference from the variable profile_cpu_callback_nb.17240 to the function .devinit.text:profile_cpu_callback()
WARNING: o-x86_64/kernel/built-in.o(.data+0x3fa0): Section mismatch in reference from the variable workqueue_cpu_callback_nb.14663 to the function .devinit.text:workqueue_cpu_callback()
WARNING: o-x86_64/kernel/built-in.o(.data+0xe280): Section mismatch in reference from the variable relay_hotcpu_callback_nb.19247 to the function .cpuinit.text:relay_hotcpu_callback()

Additional warnings are silenced with this change but
they are left put.

This patch is just a workaround for the bad practice
to use __cpuinit to annotate code solely used for
HOTPLUG_CPU.

Signed-off-by: Sam Ravnborg <sam@...nborg.org>
Cc: Gautham R Shenoy <ego@...ibm.com>
---
 include/linux/cpu.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 0be8d65..cebb8c0 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -109,7 +109,7 @@ static inline void cpuhotplug_mutex_unlock(struct mutex *cpu_hp_mutex)
 extern void get_online_cpus(void);
 extern void put_online_cpus(void);
 #define hotcpu_notifier(fn, pri) {				\
-	static struct notifier_block fn##_nb =			\
+	static struct notifier_block fn##_nb __refdata =	\
 		{ .notifier_call = fn, .priority = pri };	\
 	register_cpu_notifier(&fn##_nb);			\
 }
-- 
1.5.4.rc3.14.g44397

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