make smp_prepare_cpu to a weak function

make smp_prepare_cpu to a weak function

[Ashok Raj]

Hi Andrew

This is just a cleanup, the existing code seems to trigger
compile errors since smp_prepar_cpu() is defined with ARCH_HAS...
and its not easy to either introduce a arch call, or ideally remove it
finally. This is against 2.6.12-rc3-mm3

Cheers,
ashok
----

I really wish smp_prepare_cpu() would disappear eventually. 
In the interim this is ideally a weak function, so we dont end up 
changing several places to define this dummy in headers.

Today since the dummy declaration is done only in drivers/base/cpu.c
but the function is called in kernel/power/smp.c i get undefined
reference in my cpu hotplug code for x86_64 under development.

Signed-off-by: Ashok Raj <ashok.raj@intel.com>

Index: linux-2.6.12-rc3-mm3/include/asm-i386/smp.h
===================================================================
--- linux-2.6.12-rc3-mm3.orig/include/asm-i386/smp.h	2005-05-05 09:56:47.000000000 -0700
+++ linux-2.6.12-rc3-mm3/include/asm-i386/smp.h	2005-05-05 16:20:59.544474384 -0700
@@ -51,9 +51,6 @@
 #ifdef CONFIG_HOTPLUG_CPU
 extern void cpu_exit_clear(void);
 extern void cpu_uninit(void);
-
-#define __HAVE_ARCH_SMP_PREPARE_CPU
-extern int smp_prepare_cpu(int cpu);
 #endif
 
 /*
Index: linux-2.6.12-rc3-mm3/drivers/base/cpu.c
===================================================================
--- linux-2.6.12-rc3-mm3.orig/drivers/base/cpu.c	2005-05-05 09:56:45.000000000 -0700
+++ linux-2.6.12-rc3-mm3/drivers/base/cpu.c	2005-05-05 17:01:26.533515968 -0700
@@ -16,9 +16,10 @@
 EXPORT_SYMBOL(cpu_sysdev_class);
 
 #ifdef CONFIG_HOTPLUG_CPU
-#ifndef __HAVE_ARCH_SMP_PREPARE_CPU
-#define smp_prepare_cpu(cpu) (0)
-#endif
+int __attribute__((weak)) smp_prepare_cpu (int cpu)
+{
+	return 0;
+}
 
 static ssize_t show_online(struct sys_device *dev, char *buf)
 {
@@ -41,7 +42,7 @@
 		break;
 	case '1':
 		ret = smp_prepare_cpu(cpu->sysdev.id);
-		if (ret == 0)
+		if (!ret)
 			ret = cpu_up(cpu->sysdev.id);
 		if (!ret)
 			kobject_hotplug(&dev->kobj, KOBJ_ONLINE);
Index: linux-2.6.12-rc3-mm3/include/linux/cpu.h
===================================================================
--- linux-2.6.12-rc3-mm3.orig/include/linux/cpu.h	2005-04-20 17:03:16.000000000 -0700
+++ linux-2.6.12-rc3-mm3/include/linux/cpu.h	2005-05-05 16:43:18.048990768 -0700
@@ -69,6 +69,7 @@
 	register_cpu_notifier(&fn##_nb);			\
 }
 int cpu_down(unsigned int cpu);
+extern int __attribute__((weak)) smp_prepare_cpu(int cpu);
 #define cpu_is_offline(cpu) unlikely(!cpu_online(cpu))
 #else
 #define lock_cpu_hotplug()	do { } while (0)
-- 
Cheers,
Ashok Raj
- Open Source Technology Center

Re: make smp_prepare_cpu to a weak function

[Arjan van de Ven]

On Thu, 2005-05-05 at 17:07 -0700, Ashok Raj wrote:
> +int __attribute__((weak)) smp_prepare_cpu (int cpu)
> +{
> +	return 0;
> +}


ehhh what does this attribute mean here?????

Re: make smp_prepare_cpu to a weak function

[Ashok Raj]

On Thu, May 05, 2005 at 08:40:27PM -0400, Arjan van de Ven wrote:
> On Thu, 2005-05-05 at 17:07 -0700, Ashok Raj wrote:
> > +int __attribute__((weak)) smp_prepare_cpu (int cpu)
> > +{
> > +	return 0;
> > +}
> 
> 
> ehhh what does this attribute mean here?????
> 
> 

This function exists only for i386. Today for smp suspend they are using
cpu hotplug code, but since i386 startup code is not like
true smp bringup, so there is this hack to prepare something before calling
__cpu_up().

This is just to provide a default implementation, in the case arch
doesnt provide a smp_prepare_cpu(). 

Hope i answered the right question, unless you have something subtle here :-(

Cheers,
ashok
-- 
Cheers,
Ashok Raj
- Open Source Technology Center