arch/x86/um/asm/barrier.h

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

File Facts

System
Linux kernel
Corpus path
arch/x86/um/asm/barrier.h
Extension
.h
Size
773 bytes
Lines
30
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_UM_BARRIER_H_
#define _ASM_UM_BARRIER_H_

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

/*
 * Force strict CPU ordering.
 * And yes, this is required on UP too when we're talking
 * to devices.
 */
#ifdef CONFIG_X86_32

#define mb()	alternative("lock addl $0,0(%%esp)", "mfence", X86_FEATURE_XMM2)
#define rmb()	alternative("lock addl $0,0(%%esp)", "lfence", X86_FEATURE_XMM2)
#define wmb()	alternative("lock addl $0,0(%%esp)", "sfence", X86_FEATURE_XMM)

#else /* CONFIG_X86_32 */

#define mb()	asm volatile("mfence" : : : "memory")
#define rmb()	asm volatile("lfence" : : : "memory")
#define wmb()	asm volatile("sfence" : : : "memory")

#endif /* CONFIG_X86_32 */

#include <asm-generic/barrier.h>

#endif

Annotation

Implementation Notes