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 alternative_smp("lock; subl $1,(%0)\n\t" \
26 "call " helper "\n\t" \
31 #define __build_read_lock_const(rw, helper) \
32 alternative_smp("lock; subl $1,%0\n\t" \
36 "call " helper "\n\t" \
40 "=m" (*(volatile int *)rw) : : "memory")
42 #define __build_read_lock(rw, helper) do { \
43 if (__builtin_constant_p(rw)) \
44 __build_read_lock_const(rw, helper); \
46 __build_read_lock_ptr(rw, helper); \
49 #define __build_write_lock_ptr(rw, helper) \
50 alternative_smp("lock; subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
52 "call " helper "\n\t" \
54 "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t", \
57 #define __build_write_lock_const(rw, helper) \
58 alternative_smp("lock; subl $" RW_LOCK_BIAS_STR ",%0\n\t" \
62 "call " helper "\n\t" \
65 "subl $" RW_LOCK_BIAS_STR ",%0\n\t", \
66 "=m" (*(volatile int *)rw) : : "memory")
68 #define __build_write_lock(rw, helper) do { \
69 if (__builtin_constant_p(rw)) \
70 __build_write_lock_const(rw, helper); \
72 __build_write_lock_ptr(rw, helper); \