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Commit a378d933 authored by H. Peter Anvin's avatar H. Peter Anvin
Browse files

x86, asm: Merge cmpxchg_486_u64() and cmpxchg8b_emu() 



We have two functions for doing exactly the same thing -- emulating
cmpxchg8b on 486 and older hardware -- with different calling
conventions, and yet doing the same thing.  Drop the C version and use
the assembly version, via alternatives, for both the local and
non-local versions of cmpxchg8b.

Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
LKML-Reference: <AANLkTikAmaDPji-TVDarmG1yD=fwbffcsmEU=YEuP+8r@mail.gmail.com>
parent 90c8f92f

arch/x86/include/asm/cmpxchg_32.h

+14 −16
Original line number Diff line number Diff line
@@ -246,8 +246,6 @@ static inline unsigned long cmpxchg_386(volatile void *ptr, unsigned long old, 
 * to simulate the cmpxchg8b on the 80386 and 80486 CPU.

 */



extern unsigned long long cmpxchg_486_u64(volatile void *, u64, u64);



#define cmpxchg64(ptr, o, n)					\

({								\

	__typeof__(*(ptr)) __ret;				\
@@ -265,20 +263,20 @@ extern unsigned long long cmpxchg_486_u64(volatile void *, u64, u64); 
	__ret; })







#define cmpxchg64_local(ptr, o, n)				\

({								\

	__typeof__(*(ptr)) __ret;				\

	if (likely(boot_cpu_data.x86 > 4))				\

		__ret = (__typeof__(*(ptr)))__cmpxchg64_local((ptr),	\

				(unsigned long long)(o),		\

				(unsigned long long)(n));		\

	else								\

		__ret = (__typeof__(*(ptr)))cmpxchg_486_u64((ptr),	\

				(unsigned long long)(o),		\

				(unsigned long long)(n));		\

	__ret;								\

})

	__typeof__(*(ptr)) __old = (o);				\

	__typeof__(*(ptr)) __new = (n);				\

	alternative_io("call cmpxchg8b_emu",			\

		       "cmpxchg8b (%%esi)" ,			\

		       X86_FEATURE_CX8,				\

		       "=A" (__ret),				\

		       "S" ((ptr)), "0" (__old),		\

		       "b" ((unsigned int)__new),		\

		       "c" ((unsigned int)(__new>>32))		\

		       : "memory");				\

	__ret; })



#endif

arch/x86/lib/cmpxchg.c

+0 −18
Original line number Diff line number Diff line
@@ -52,21 +52,3 @@ unsigned long cmpxchg_386_u32(volatile void *ptr, u32 old, u32 new) 
}

EXPORT_SYMBOL(cmpxchg_386_u32);

#endif
 


#ifndef CONFIG_X86_CMPXCHG64

unsigned long long cmpxchg_486_u64(volatile void *ptr, u64 old, u64 new)

{

	u64 prev;

	unsigned long flags;



	/* Poor man's cmpxchg8b for 386 and 486. Unsuitable for SMP */

	local_irq_save(flags);

	prev = *(u64 *)ptr;

	if (prev == old)

		*(u64 *)ptr = new;

	local_irq_restore(flags);

	return prev;

}

EXPORT_SYMBOL(cmpxchg_486_u64);

#endif