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Commit 53e86b91 authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
Browse files

[PATCH] i386: generic cmpxchg 



- Make cmpxchg generally available on the i386 platform.

- Provide emulation of cmpxchg suitable for uniprocessor if built and run on
  386.

From: Christoph Lameter <clameter@sgi.com>

- Cut down patch and small style changes.

Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent dbdf65b1

arch/i386/kernel/cpu/intel.c

+48 −0
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 
#include <linux/bitops.h>

#include <linux/smp.h>

#include <linux/thread_info.h>

#include <linux/module.h>



#include <asm/processor.h>

#include <asm/msr.h>
@@ -264,5 +265,52 @@ __init int intel_cpu_init(void) 
	return 0;

}



#ifndef CONFIG_X86_CMPXCHG

unsigned long cmpxchg_386_u8(volatile void *ptr, u8 old, u8 new)

{

	u8 prev;

	unsigned long flags;



	/* Poor man's cmpxchg for 386. Unsuitable for SMP */

	local_irq_save(flags);

	prev = *(u8 *)ptr;

	if (prev == old)

		*(u8 *)ptr = new;

	local_irq_restore(flags);

	return prev;

}

EXPORT_SYMBOL(cmpxchg_386_u8);



unsigned long cmpxchg_386_u16(volatile void *ptr, u16 old, u16 new)

{

	u16 prev;

	unsigned long flags;



	/* Poor man's cmpxchg for 386. Unsuitable for SMP */

	local_irq_save(flags);

	prev = *(u16 *)ptr;

	if (prev == old)

		*(u16 *)ptr = new;

	local_irq_restore(flags);

	return prev;

}

EXPORT_SYMBOL(cmpxchg_386_u16);



unsigned long cmpxchg_386_u32(volatile void *ptr, u32 old, u32 new)

{

	u32 prev;

	unsigned long flags;



	/* Poor man's cmpxchg for 386. Unsuitable for SMP */

	local_irq_save(flags);

	prev = *(u32 *)ptr;

	if (prev == old)

		*(u32 *)ptr = new;

	local_irq_restore(flags);

	return prev;

}

EXPORT_SYMBOL(cmpxchg_386_u32);

#endif



// arch_initcall(intel_cpu_init);

include/asm-i386/system.h

+39 −3
Original line number Diff line number Diff line
@@ -263,6 +263,10 @@ static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int siz 


#ifdef CONFIG_X86_CMPXCHG

#define __HAVE_ARCH_CMPXCHG 1

#define cmpxchg(ptr,o,n)\

	((__typeof__(*(ptr)))__cmpxchg((ptr),(unsigned long)(o),\

					(unsigned long)(n),sizeof(*(ptr))))

#endif



static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,

				      unsigned long new, int size)
@@ -291,10 +295,42 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, 
	return old;

}



#define cmpxchg(ptr,o,n)\

	((__typeof__(*(ptr)))__cmpxchg((ptr),(unsigned long)(o),\

					(unsigned long)(n),sizeof(*(ptr))))

#ifndef CONFIG_X86_CMPXCHG

/*

 * Building a kernel capable running on 80386. It may be necessary to

 * simulate the cmpxchg on the 80386 CPU. For that purpose we define

 * a function for each of the sizes we support.

 */



extern unsigned long cmpxchg_386_u8(volatile void *, u8, u8);

extern unsigned long cmpxchg_386_u16(volatile void *, u16, u16);

extern unsigned long cmpxchg_386_u32(volatile void *, u32, u32);



static inline unsigned long cmpxchg_386(volatile void *ptr, unsigned long old,

				      unsigned long new, int size)

{

	switch (size) {

	case 1:

		return cmpxchg_386_u8(ptr, old, new);

	case 2:

		return cmpxchg_386_u16(ptr, old, new);

	case 4:

		return cmpxchg_386_u32(ptr, old, new);

	}

	return old;

}



#define cmpxchg(ptr,o,n)						\

({									\

	__typeof__(*(ptr)) __ret;					\

	if (likely(boot_cpu_data.x86 > 3))				\

		__ret = __cmpxchg((ptr), (unsigned long)(o),		\

					(unsigned long)(n), sizeof(*(ptr))); \

	else								\

		__ret = cmpxchg_386((ptr), (unsigned long)(o),		\

					(unsigned long)(n), sizeof(*(ptr))); \

	__ret;								\

})

#endif



#ifdef CONFIG_X86_CMPXCHG64