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Date: Tue, 11 Jul 2006 23:46:05 -0700
From: Andrew Morton <akpm@osdl.org>
To: Fernando Luis =?ISO-8859-1?B?VuF6cXVleg==?= Cao 
	<fernando@oss.ntt.co.jp>
Cc: vgoyal@in.ibm.com, ebiederm@xmission.com, ak@suse.de,
       James.Bottomley@steeleye.com, linux-kernel@vger.kernel.org,
       fastboot@lists.osdl.org
Subject: Re: [PATCH 1/4] stack overflow safe kdump (2.6.18-rc1-i386) -
 safe_smp_processor_id
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On Tue, 11 Jul 2006 15:05:18 +0900
Fernando Luis Vázquez Cao <fernando@oss.ntt.co.jp> wrote:
> ...

With CONFIG_SMP=n:

arch/i386/kernel/crash.c: In function 'crash_save_self':
arch/i386/kernel/crash.c:91: warning: implicit declaration of function 'safe_smp_processor_id'

And it fails to link.


> --- linux-2.6.18-rc1/include/asm-i386/smp.h	2006-07-11 10:11:44.000000000 +0900
> +++ linux-2.6.18-rc1-sof/include/asm-i386/smp.h	2006-07-11 14:05:28.000000000 +0900
> @@ -89,12 +89,14 @@ static __inline int logical_smp_processo
>  
>  #endif
>  
> +extern int safe_smp_processor_id(void);
>  extern int __cpu_disable(void);
>  extern void __cpu_die(unsigned int cpu);
>  #endif /* !__ASSEMBLY__ */
>  
>  #else /* CONFIG_SMP */
>  
> +#define safe_smp_processor_id()		0
>  #define cpu_physical_id(cpu)		boot_cpu_physical_apicid
>  
>  #define NO_PROC_ID		0xFF		/* No processor magic marker */

The reason for this is that include/linux/smp.h only includes asm/smp.h if
CONFIG_SMP=y.  This is not the cleverest thing we've ever done.

I fixed that in cowardly fashion:


--- a/arch/i386/kernel/crash.c~stack-overflow-safe-kdump-crash_use_safe_smp_processor_id-fix
+++ a/arch/i386/kernel/crash.c
@@ -23,6 +23,7 @@
 #include <asm/hw_irq.h>
 #include <asm/apic.h>
 #include <asm/kdebug.h>
+#include <asm/smp.h>
 
 #include <mach_ipi.h>
 
_