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/* include/asm-x86_64/rwlock.h
*
* Helpers used by both rw spinlocks and rw semaphores.
*
* Based in part on code from semaphore.h and
* spinlock.h Copyright 1996 Linus Torvalds.
*
* Copyright 1999 Red Hat, Inc.
* Copyright 2001,2002 SuSE labs
*
* Written by Benjamin LaHaise.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#ifndef _ASM_X86_64_RWLOCK_H
#define _ASM_X86_64_RWLOCK_H
#include <linux/stringify.h>
#define RW_LOCK_BIAS 0x01000000
#define RW_LOCK_BIAS_STR "0x01000000"
#define __build_read_lock_ptr(rw, helper) \
asm volatile(LOCK_PREFIX "subl $1,(%0)\n\t" \
"js 2f\n" \
"1:\n" \
LOCK_SECTION_START("") \
"2:\tcall " helper "\n\t" \
"jmp 1b\n" \
LOCK_SECTION_END \
::"a" (rw) : "memory")
#define __build_read_lock_const(rw, helper) \
asm volatile(LOCK_PREFIX "subl $1,%0\n\t" \
"js 2f\n" \
"1:\n" \
LOCK_SECTION_START("") \
"2:\tpushq %%rax\n\t" \
"leaq %0,%%rax\n\t" \
"call " helper "\n\t" \
"popq %%rax\n\t" \
"jmp 1b\n" \
LOCK_SECTION_END \
:"=m" (*((volatile int *)rw))::"memory")
#define __build_read_lock(rw, helper) do { \
if (__builtin_constant_p(rw)) \
__build_read_lock_const(rw, helper); \
else \
__build_read_lock_ptr(rw, helper); \
} while (0)
#define __build_write_lock_ptr(rw, helper) \
asm volatile(LOCK_PREFIX "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
"jnz 2f\n" \
"1:\n" \
LOCK_SECTION_START("") \
"2:\tcall " helper "\n\t" \
"jmp 1b\n" \
LOCK_SECTION_END \
::"a" (rw) : "memory")
#define __build_write_lock_const(rw, helper) \
asm volatile(LOCK_PREFIX "subl $" RW_LOCK_BIAS_STR ",%0\n\t" \
"jnz 2f\n" \
"1:\n" \
LOCK_SECTION_START("") \
"2:\tpushq %%rax\n\t" \
"leaq %0,%%rax\n\t" \
"call " helper "\n\t" \
"popq %%rax\n\t" \
"jmp 1b\n" \
LOCK_SECTION_END \
:"=m" (*((volatile long *)rw))::"memory")
#define __build_write_lock(rw, helper) do { \
if (__builtin_constant_p(rw)) \
__build_write_lock_const(rw, helper); \
else \
__build_write_lock_ptr(rw, helper); \
} while (0)
#endif
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