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Commit 53e86b91 authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
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[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
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+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);
+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