arch/x86/include/asm/barrier.h

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

File Facts

System
Linux kernel
Corpus path
arch/x86/include/asm/barrier.h
Extension
.h
Size
2419 bytes
Lines
84
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

#ifndef _ASM_X86_BARRIER_H
#define _ASM_X86_BARRIER_H

#include <asm/alternative.h>
#include <asm/nops.h>

/*
 * Force strict CPU ordering.
 * And yes, this might be required on UP too when we're talking
 * to devices.
 */

#ifdef CONFIG_X86_32
#define mb() asm volatile(ALTERNATIVE("lock addl $0,-4(%%esp)", "mfence", \
				      X86_FEATURE_XMM2) ::: "memory", "cc")
#define rmb() asm volatile(ALTERNATIVE("lock addl $0,-4(%%esp)", "lfence", \
				       X86_FEATURE_XMM2) ::: "memory", "cc")
#define wmb() asm volatile(ALTERNATIVE("lock addl $0,-4(%%esp)", "sfence", \
				       X86_FEATURE_XMM2) ::: "memory", "cc")
#else
#define __mb()	asm volatile("mfence":::"memory")
#define __rmb()	asm volatile("lfence":::"memory")
#define __wmb()	asm volatile("sfence" ::: "memory")
#endif

/**
 * array_index_mask_nospec() - generate a mask that is ~0UL when the
 * 	bounds check succeeds and 0 otherwise
 * @index: array element index
 * @size: number of elements in array
 *
 * Returns:
 *     0 - (index < size)
 */
#define array_index_mask_nospec(idx,sz) ({	\
	typeof((idx)+(sz)) __idx = (idx);	\
	typeof(__idx) __sz = (sz);		\
	unsigned long __mask;			\
	asm volatile ("cmp %1,%2; sbb %0,%0"	\
			:"=r" (__mask)		\
			:ASM_INPUT_G (__sz),	\
			 "r" (__idx)		\
			:"cc");			\
	__mask; })

/* Prevent speculative execution past this barrier. */
#define barrier_nospec() alternative("", "lfence", X86_FEATURE_LFENCE_RDTSC)

#define __dma_rmb()	barrier()
#define __dma_wmb()	barrier()

#define __smp_mb()	asm volatile("lock addl $0,-4(%%" _ASM_SP ")" ::: "memory", "cc")

#define __smp_rmb()	dma_rmb()
#define __smp_wmb()	barrier()
#define __smp_store_mb(var, value) do { (void)xchg(&var, value); } while (0)

#define __smp_store_release(p, v)					\
do {									\
	compiletime_assert_atomic_type(*p);				\
	barrier();							\
	WRITE_ONCE(*p, v);						\
} while (0)

#define __smp_load_acquire(p)						\
({									\
	typeof(*p) ___p1 = READ_ONCE(*p);				\
	compiletime_assert_atomic_type(*p);				\
	barrier();							\
	___p1;								\
})

/* Atomic operations are already serializing on x86 */
#define __smp_mb__before_atomic()	do { } while (0)
#define __smp_mb__after_atomic()	do { } while (0)

/* Writing to CR3 provides a full memory barrier in switch_mm(). */
#define smp_mb__after_switch_mm()	do { } while (0)

#include <asm-generic/barrier.h>

#endif /* _ASM_X86_BARRIER_H */

Annotation

Implementation Notes