arch/x86/include/asm/cmpxchg.h

Source file repositories/reference/linux-study-clean/arch/x86/include/asm/cmpxchg.h

File Facts

System
Linux kernel
Corpus path
arch/x86/include/asm/cmpxchg.h
Extension
.h
Size
7428 bytes
Lines
245
Domain
Architecture Layer
Bucket
arch/x86
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

switch (sizeof(*(ptr))) {				\
		case __X86_CASE_B:					\
			asm_inline volatile (lock #op "b %b0, %1"	\
				      : "+q" (__ret), "+m" (*(ptr))	\
				      : : "memory", "cc");		\
			break;						\
		case __X86_CASE_W:					\
			asm_inline volatile (lock #op "w %w0, %1"	\
				      : "+r" (__ret), "+m" (*(ptr))	\
				      : : "memory", "cc");		\
			break;						\
		case __X86_CASE_L:					\
			asm_inline volatile (lock #op "l %0, %1"	\
				      : "+r" (__ret), "+m" (*(ptr))	\
				      : : "memory", "cc");		\
			break;						\
		case __X86_CASE_Q:					\
			asm_inline volatile (lock #op "q %q0, %1"	\
				      : "+r" (__ret), "+m" (*(ptr))	\
				      : : "memory", "cc");		\
			break;						\
		default:						\
			__ ## op ## _wrong_size();			\
		}							\
		__ret;							\
	})

/*
 * 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 arch_xchg(ptr, v)	__xchg_op((ptr), (v), xchg, "")

/*
 * Atomic compare and exchange.  Compare OLD with MEM, if identical,
 * store NEW in MEM.  Return the initial value in MEM.  Success is
 * indicated by comparing RETURN with OLD.
 */
#define __raw_cmpxchg(ptr, old, new, size, lock)			\
({									\
	__typeof__(*(ptr)) __ret;					\
	__typeof__(*(ptr)) __old = (old);				\
	__typeof__(*(ptr)) __new = (new);				\
	switch (size) {							\
	case __X86_CASE_B:						\
	{								\
		volatile u8 *__ptr = (volatile u8 *)(ptr);		\
		asm_inline volatile(lock "cmpxchgb %2, %1"		\
			     : "=a" (__ret), "+m" (*__ptr)		\
			     : "q" (__new), "0" (__old)			\
			     : "memory");				\
		break;							\
	}								\
	case __X86_CASE_W:						\
	{								\
		volatile u16 *__ptr = (volatile u16 *)(ptr);		\
		asm_inline volatile(lock "cmpxchgw %2, %1"		\
			     : "=a" (__ret), "+m" (*__ptr)		\
			     : "r" (__new), "0" (__old)			\
			     : "memory");				\
		break;							\
	}								\
	case __X86_CASE_L:						\
	{								\
		volatile u32 *__ptr = (volatile u32 *)(ptr);		\
		asm_inline volatile(lock "cmpxchgl %2, %1"		\
			     : "=a" (__ret), "+m" (*__ptr)		\
			     : "r" (__new), "0" (__old)			\
			     : "memory");				\
		break;							\
	}								\
	case __X86_CASE_Q:						\
	{								\
		volatile u64 *__ptr = (volatile u64 *)(ptr);		\
		asm_inline volatile(lock "cmpxchgq %2, %1"		\
			     : "=a" (__ret), "+m" (*__ptr)		\
			     : "r" (__new), "0" (__old)			\
			     : "memory");				\
		break;							\
	}								\
	default:							\
		__cmpxchg_wrong_size();					\
	}								\
	__ret;								\
})

#define __cmpxchg(ptr, old, new, size)					\
	__raw_cmpxchg((ptr), (old), (new), (size), LOCK_PREFIX)

Annotation

Implementation Notes