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Commit 4532b305 authored by H. Peter Anvin's avatar H. Peter Anvin
Browse files

x86, asm: Clean up and simplify <asm/cmpxchg.h> 



Remove the __xg() hack to create a memory barrier near xchg and
cmpxchg; it has been there since 1.3.11 but should not be necessary
with "asm volatile" and a "memory" clobber, neither of which were
there in the original implementation.

However, we *should* make this a volatile reference.

Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
LKML-Reference: <AANLkTikAmaDPji-TVDarmG1yD=fwbffcsmEU=YEuP+8r@mail.gmail.com>
parent 69309a05

arch/x86/include/asm/cmpxchg_32.h

+42 −33
Original line number Diff line number Diff line
@@ -11,38 +11,42 @@ 
extern void __xchg_wrong_size(void);



/*

 * Note: no "lock" prefix even on SMP: xchg always implies lock anyway

 * Note 2: xchg has side effect, so that attribute volatile is necessary,

 *	  but generally the primitive is invalid, *ptr is output argument. --ANK

 * Note: no "lock" prefix even on SMP: xchg always implies lock anyway.

 * Since this is generally used to protect other memory information, we

 * use "asm volatile" and "memory" clobbers to prevent gcc from moving

 * information around.

 */



struct __xchg_dummy {

	unsigned long a[100];

};

#define __xg(x) ((struct __xchg_dummy *)(x))



#define __xchg(x, ptr, size)						\

({									\

	__typeof(*(ptr)) __x = (x);					\

	switch (size) {							\

	case 1:								\

		asm volatile("xchgb %b0,%1"				\

			     : "=q" (__x), "+m" (*__xg(ptr))		\

	{								\

		volatile u8 *__ptr = (volatile u8 *)(ptr);		\

		asm volatile("xchgb %0,%1"				\

			     : "=q" (__x), "+m" (*__ptr)		\

			     : "0" (__x)				\

			     : "memory");				\

		break;							\

	}								\

	case 2:								\

		asm volatile("xchgw %w0,%1"				\

			     : "=r" (__x), "+m" (*__xg(ptr))		\

	{								\

		volatile u16 *__ptr = (volatile u16 *)(ptr);		\

		asm volatile("xchgw %0,%1"				\

			     : "=r" (__x), "+m" (*__ptr)		\

			     : "0" (__x)				\

			     : "memory");				\

		break;							\

	}								\

	case 4:								\

	{								\

		volatile u32 *__ptr = (volatile u32 *)(ptr);		\

		asm volatile("xchgl %0,%1"				\

			     : "=r" (__x), "+m" (*__xg(ptr))		\

			     : "=r" (__x), "+m" (*__ptr)		\

			     : "0" (__x)				\

			     : "memory");				\

		break;							\

	}								\

	default:							\

		__xchg_wrong_size();					\

	}								\
@@ -94,23 +98,32 @@ extern void __cmpxchg_wrong_size(void); 
	__typeof__(*(ptr)) __new = (new);				\

	switch (size) {							\

	case 1:								\

		asm volatile(lock "cmpxchgb %b2,%1"			\

			     : "=a" (__ret), "+m" (*__xg(ptr))		\

	{								\

		volatile u8 *__ptr = (volatile u8 *)(ptr);		\

		asm volatile(lock "cmpxchgb %2,%1"			\

			     : "=a" (__ret), "+m" (*__ptr)		\

			     : "q" (__new), "0" (__old)			\

			     : "memory");				\

		break;							\

	}								\

	case 2:								\

		asm volatile(lock "cmpxchgw %w2,%1"			\

			     : "=a" (__ret), "+m" (*__xg(ptr))		\

	{								\

		volatile u16 *__ptr = (volatile u16 *)(ptr);		\

		asm volatile(lock "cmpxchgw %2,%1"			\

			     : "=a" (__ret), "+m" (*__ptr)		\

			     : "r" (__new), "0" (__old)			\

			     : "memory");				\

		break;							\

	}								\

	case 4:								\

	{								\

		volatile u32 *__ptr = (volatile u32 *)(ptr);		\

		asm volatile(lock "cmpxchgl %2,%1"			\

			     : "=a" (__ret), "+m" (*__xg(ptr))		\

			     : "=a" (__ret), "+m" (*__ptr)		\

			     : "r" (__new), "0" (__old)			\

			     : "memory");				\

		break;							\

	}								\

	default:							\

		__cmpxchg_wrong_size();					\

	}								\
@@ -148,31 +161,27 @@ extern void __cmpxchg_wrong_size(void); 
					       (unsigned long long)(n)))

#endif



static inline unsigned long long __cmpxchg64(volatile void *ptr,

					     unsigned long long old,

					     unsigned long long new)

static inline u64 __cmpxchg64(volatile u64 *ptr, u64 old, u64 new)

{

	unsigned long long prev;

	u64 prev;

	asm volatile(LOCK_PREFIX "cmpxchg8b %1"

		     : "=A" (prev),

		       "+m" (*__xg(ptr))

		     : "b" ((unsigned long)new),

		       "c" ((unsigned long)(new >> 32)),

		       "+m" (*ptr)

		     : "b" ((u32)new),

		       "c" ((u32)(new >> 32)),

		       "0" (old)

		     : "memory");

	return prev;

}



static inline unsigned long long __cmpxchg64_local(volatile void *ptr,

						   unsigned long long old,

						   unsigned long long new)

static inline u64 __cmpxchg64_local(volatile u64 *ptr, u64 old, u64 new)

{

	unsigned long long prev;

	u64 prev;

	asm volatile("cmpxchg8b %1"

		     : "=A" (prev),

		       "+m" (*__xg(ptr))

		     : "b" ((unsigned long)new),

		       "c" ((unsigned long)(new >> 32)),

		       "+m" (*ptr)

		     : "b" ((u32)new),

		       "c" ((u32)(new >> 32)),

		       "0" (old)

		     : "memory");

	return prev;

arch/x86/include/asm/cmpxchg_64.h

+42 −19
Original line number Diff line number Diff line
@@ -3,8 +3,6 @@ 


#include <asm/alternative.h> /* Provides LOCK_PREFIX */



#define __xg(x) ((volatile long *)(x))



static inline void set_64bit(volatile u64 *ptr, u64 val)

{

	*ptr = val;
@@ -14,38 +12,51 @@ extern void __xchg_wrong_size(void); 
extern void __cmpxchg_wrong_size(void);



/*

 * Note: no "lock" prefix even on SMP: xchg always implies lock anyway

 * Note 2: xchg has side effect, so that attribute volatile is necessary,

 *	  but generally the primitive is invalid, *ptr is output argument. --ANK

 * Note: no "lock" prefix even on SMP: xchg always implies lock anyway.

 * Since this is generally used to protect other memory information, we

 * use "asm volatile" and "memory" clobbers to prevent gcc from moving

 * information around.

 */

#define __xchg(x, ptr, size)						\

({									\

	__typeof(*(ptr)) __x = (x);					\

	switch (size) {							\

	case 1:								\

		asm volatile("xchgb %b0,%1"				\

			     : "=q" (__x), "+m" (*__xg(ptr))		\

	{								\

		volatile u8 *__ptr = (volatile u8 *)(ptr);		\

		asm volatile("xchgb %0,%1"				\

			     : "=q" (__x), "+m" (*__ptr)		\

			     : "0" (__x)				\

			     : "memory");				\

		break;							\

	}								\

	case 2:								\

		asm volatile("xchgw %w0,%1"				\

			     : "=r" (__x), "+m" (*__xg(ptr))		\

	{								\

		volatile u16 *__ptr = (volatile u16 *)(ptr);		\

		asm volatile("xchgw %0,%1"				\

			     : "=r" (__x), "+m" (*__ptr)		\

			     : "0" (__x)				\

			     : "memory");				\

		break;							\

	}								\

	case 4:								\

		asm volatile("xchgl %k0,%1"				\

			     : "=r" (__x), "+m" (*__xg(ptr))		\

	{								\

		volatile u32 *__ptr = (volatile u32 *)(ptr);		\

		asm volatile("xchgl %0,%1"				\

			     : "=r" (__x), "+m" (*__ptr)		\

			     : "0" (__x)				\

			     : "memory");				\

		break;							\

	}								\

	case 8:								\

	{								\

		volatile u64 *__ptr = (volatile u64 *)(ptr);		\

		asm volatile("xchgq %0,%1"				\

			     : "=r" (__x), "+m" (*__xg(ptr))		\

			     : "=r" (__x), "+m" (*__ptr)		\

			     : "0" (__x)				\

			     : "memory");				\

		break;							\

	}								\

	default:							\

		__xchg_wrong_size();					\

	}								\
@@ -69,29 +80,41 @@ extern void __cmpxchg_wrong_size(void); 
	__typeof__(*(ptr)) __new = (new);				\

	switch (size) {							\

	case 1:								\

		asm volatile(lock "cmpxchgb %b2,%1"			\

			     : "=a" (__ret), "+m" (*__xg(ptr))		\

	{								\

		volatile u8 *__ptr = (volatile u8 *)(ptr);		\

		asm volatile(lock "cmpxchgb %2,%1"			\

			     : "=a" (__ret), "+m" (*__ptr)		\

			     : "q" (__new), "0" (__old)			\

			     : "memory");				\

		break;							\

	}								\

	case 2:								\

		asm volatile(lock "cmpxchgw %w2,%1"			\

			     : "=a" (__ret), "+m" (*__xg(ptr))		\

	{								\

		volatile u16 *__ptr = (volatile u16 *)(ptr);		\

		asm volatile(lock "cmpxchgw %2,%1"			\

			     : "=a" (__ret), "+m" (*__ptr)		\

			     : "r" (__new), "0" (__old)			\

			     : "memory");				\

		break;							\

	}								\

	case 4:								\

		asm volatile(lock "cmpxchgl %k2,%1"			\

			     : "=a" (__ret), "+m" (*__xg(ptr))		\

	{								\

		volatile u32 *__ptr = (volatile u32 *)(ptr);		\

		asm volatile(lock "cmpxchgl %2,%1"			\

			     : "=a" (__ret), "+m" (*__ptr)		\

			     : "r" (__new), "0" (__old)			\

			     : "memory");				\

		break;							\

	}								\

	case 8:								\

	{								\

		volatile u64 *__ptr = (volatile u64 *)(ptr);		\

		asm volatile(lock "cmpxchgq %2,%1"			\

			     : "=a" (__ret), "+m" (*__xg(ptr))		\

			     : "=a" (__ret), "+m" (*__ptr)		\

			     : "r" (__new), "0" (__old)			\

			     : "memory");				\

		break;							\

	}								\

	default:							\

		__cmpxchg_wrong_size();					\

	}								\