1 /* include/asm-i386/rwlock.h
3 * Helpers used by both rw spinlocks and rw semaphores.
5 * Based in part on code from semaphore.h and
6 * spinlock.h Copyright 1996 Linus Torvalds.
8 * Copyright 1999 Red Hat, Inc.
10 * Written by Benjamin LaHaise.
12 * This program is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU General Public License
14 * as published by the Free Software Foundation; either version
15 * 2 of the License, or (at your option) any later version.
17 #ifndef _ASM_I386_RWLOCK_H
18 #define _ASM_I386_RWLOCK_H
20 #define RW_LOCK_BIAS 0x01000000
21 #define RW_LOCK_BIAS_STR "0x01000000"
23 #define __build_read_lock_ptr(rw, helper) \
24 asm volatile(LOCK "subl $1,(%0)\n\t" \
27 LOCK_SECTION_START("") \
28 "2:\tcall " helper "\n\t" \
31 ::"a" (rw) : "memory")
33 #define __build_read_lock_const(rw, helper) \
34 asm volatile(LOCK "subl $1,%0\n\t" \
37 LOCK_SECTION_START("") \
38 "2:\tpushl %%eax\n\t" \
40 "call " helper "\n\t" \
44 :"=m" (*(volatile int *)rw) : : "memory")
46 #define __build_read_lock(rw, helper) do { \
47 if (__builtin_constant_p(rw)) \
48 __build_read_lock_const(rw, helper); \
50 __build_read_lock_ptr(rw, helper); \
53 #define __build_write_lock_ptr(rw, helper) \
54 asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
57 LOCK_SECTION_START("") \
58 "2:\tcall " helper "\n\t" \
61 ::"a" (rw) : "memory")
63 #define __build_write_lock_const(rw, helper) \
64 asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",%0\n\t" \
67 LOCK_SECTION_START("") \
68 "2:\tpushl %%eax\n\t" \
70 "call " helper "\n\t" \
74 :"=m" (*(volatile int *)rw) : : "memory")
76 #define __build_write_lock(rw, helper) do { \
77 if (__builtin_constant_p(rw)) \
78 __build_write_lock_const(rw, helper); \
80 __build_write_lock_ptr(rw, helper); \