linux-kernel - Re: Solving section mismatches

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Date:	Sun, 27 Sep 2009 22:22:51 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: Solving section mismatches

On Sun, Sep 27, 2009 at 09:15:07PM +0100, Russell King - ARM Linux wrote:
> On Sun, Sep 27, 2009 at 09:47:47PM +0200, Sam Ravnborg wrote:
> > Please try this:
> > diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
> > index e0d3277..835188b 100644
> > --- a/arch/arm/kernel/smp.c
> > +++ b/arch/arm/kernel/smp.c
> > @@ -214,7 +214,7 @@ void __cpuexit __cpu_die(unsigned int cpu)
> >   * of the other hotplug-cpu capable cores, so presumably coming
> >   * out of idle fixes this.
> >   */
> > -void __cpuexit cpu_die(void)
> > +void __ref cpu_die(void)
> >  {
> >         unsigned int cpu = smp_processor_id();
> 
> That works - so can I get your ack for this entire patch please:
> 
> From: Russell King <rmk+kernel@....linux.org.uk>
> Subject: [PATCH] ARM: Fix __cpuexit section mismatch warnings
> 
> Fix:
> 
> WARNING: vmlinux.o(.text+0x247c): Section mismatch in reference from the function cpu_idle() to the function .cpuexit.text:cpu_die()
> The function cpu_idle() references a function in an exit section.
> Often the function cpu_die() has valid usage outside the exit section
> and the fix is to remove the __cpuexit annotation of cpu_die.
> 
> WARNING: vmlinux.o(.cpuexit.text+0x3c): Section mismatch in reference from the function cpu_die() to the function .cpuinit.text:secondary_start_kernel()
> The function __cpuexit cpu_die() references
> a function __cpuinit secondary_start_kernel().
> This is often seen when error handling in the exit function
> uses functionality in the init path.
> The fix is often to remove the __cpuinit annotation of
> secondary_start_kernel() so it may be used outside an init section.
> 
> Sam says:
> > The annotation of cpu_die() is wrong.
> > To be annotated __cpuexit the function shall:
> > - be used in exit context and only in exit context with HOTPLUG_CPU=n
> > - be used outside exit context with HOTPLUG_CPU=y
> 
> So, this also means __cpu_disable(), __cpu_die() and twd_timer_stop() are
> also wrong.  However, removing __cpuexit from cpu_die() creates:
> 
> WARNING: vmlinux.o(.text+0x6834): Section mismatch in reference from the function cpu_die() to the function .cpuinit.text:secondary_start_kernel()
> The function cpu_die() references
> the function __cpuinit secondary_start_kernel().
> This is often because cpu_die lacks a __cpuinit
> annotation or the annotation of secondary_start_kernel is wrong.
> 
> so fix this using __ref.
> 
> Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>

Patch looks good!
Acked-by: Sam Ravnborg <sam@...nborg.org>

	Sam
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