113fc5a6e8
xchg() and cmpxchg() modify their memory operands, not merely read them. For some versions of gcc the "memory" clobber has apparently dealt with the situation, but not for all. Originally-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: H. Peter Anvin <hpa@zytor.com> Cc: Glauber Costa <glommer@redhat.com> Cc: Avi Kivity <avi@redhat.com> Cc: Peter Palfrader <peter@palfrader.org> Cc: Greg KH <gregkh@suse.de> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Zachary Amsden <zamsden@redhat.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: <stable@kernel.org> LKML-Reference: <4C4F7277.8050306@zytor.com>
134 lines
3.5 KiB
C
134 lines
3.5 KiB
C
#ifndef _ASM_X86_CMPXCHG_64_H
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#define _ASM_X86_CMPXCHG_64_H
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#include <asm/alternative.h> /* Provides LOCK_PREFIX */
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#define __xg(x) ((volatile long *)(x))
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static inline void set_64bit(volatile unsigned long *ptr, unsigned long val)
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{
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*ptr = val;
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}
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#define _set_64bit set_64bit
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extern void __xchg_wrong_size(void);
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extern void __cmpxchg_wrong_size(void);
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/*
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* Note: no "lock" prefix even on SMP: xchg always implies lock anyway
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* Note 2: xchg has side effect, so that attribute volatile is necessary,
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* but generally the primitive is invalid, *ptr is output argument. --ANK
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*/
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#define __xchg(x, ptr, size) \
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({ \
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__typeof(*(ptr)) __x = (x); \
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switch (size) { \
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case 1: \
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asm volatile("xchgb %b0,%1" \
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: "=q" (__x), "+m" (*__xg(ptr)) \
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: "0" (__x) \
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: "memory"); \
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break; \
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case 2: \
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asm volatile("xchgw %w0,%1" \
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: "=r" (__x), "+m" (*__xg(ptr)) \
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: "0" (__x) \
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: "memory"); \
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break; \
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case 4: \
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asm volatile("xchgl %k0,%1" \
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: "=r" (__x), "+m" (*__xg(ptr)) \
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: "0" (__x) \
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: "memory"); \
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break; \
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case 8: \
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asm volatile("xchgq %0,%1" \
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: "=r" (__x), "+m" (*__xg(ptr)) \
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: "0" (__x) \
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: "memory"); \
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break; \
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default: \
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__xchg_wrong_size(); \
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} \
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__x; \
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})
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#define xchg(ptr, v) \
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__xchg((v), (ptr), sizeof(*ptr))
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#define __HAVE_ARCH_CMPXCHG 1
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/*
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* Atomic compare and exchange. Compare OLD with MEM, if identical,
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* store NEW in MEM. Return the initial value in MEM. Success is
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* indicated by comparing RETURN with OLD.
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*/
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#define __raw_cmpxchg(ptr, old, new, size, lock) \
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({ \
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__typeof__(*(ptr)) __ret; \
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__typeof__(*(ptr)) __old = (old); \
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__typeof__(*(ptr)) __new = (new); \
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switch (size) { \
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case 1: \
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asm volatile(lock "cmpxchgb %b2,%1" \
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: "=a" (__ret), "+m" (*__xg(ptr)) \
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: "q" (__new), "0" (__old) \
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: "memory"); \
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break; \
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case 2: \
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asm volatile(lock "cmpxchgw %w2,%1" \
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: "=a" (__ret), "+m" (*__xg(ptr)) \
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: "r" (__new), "0" (__old) \
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: "memory"); \
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break; \
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case 4: \
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asm volatile(lock "cmpxchgl %k2,%1" \
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: "=a" (__ret), "+m" (*__xg(ptr)) \
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: "r" (__new), "0" (__old) \
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: "memory"); \
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break; \
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case 8: \
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asm volatile(lock "cmpxchgq %2,%1" \
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: "=a" (__ret), "+m" (*__xg(ptr)) \
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: "r" (__new), "0" (__old) \
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: "memory"); \
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break; \
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default: \
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__cmpxchg_wrong_size(); \
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} \
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__ret; \
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})
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#define __cmpxchg(ptr, old, new, size) \
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__raw_cmpxchg((ptr), (old), (new), (size), LOCK_PREFIX)
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#define __sync_cmpxchg(ptr, old, new, size) \
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__raw_cmpxchg((ptr), (old), (new), (size), "lock; ")
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#define __cmpxchg_local(ptr, old, new, size) \
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__raw_cmpxchg((ptr), (old), (new), (size), "")
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#define cmpxchg(ptr, old, new) \
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__cmpxchg((ptr), (old), (new), sizeof(*ptr))
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#define sync_cmpxchg(ptr, old, new) \
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__sync_cmpxchg((ptr), (old), (new), sizeof(*ptr))
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#define cmpxchg_local(ptr, old, new) \
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__cmpxchg_local((ptr), (old), (new), sizeof(*ptr))
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#define cmpxchg64(ptr, o, n) \
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({ \
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BUILD_BUG_ON(sizeof(*(ptr)) != 8); \
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cmpxchg((ptr), (o), (n)); \
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})
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#define cmpxchg64_local(ptr, o, n) \
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({ \
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BUILD_BUG_ON(sizeof(*(ptr)) != 8); \
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cmpxchg_local((ptr), (o), (n)); \
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})
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#endif /* _ASM_X86_CMPXCHG_64_H */
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