1 /* include/asm-i386/rwlock.h
2 *
3 * Helpers used by both rw spinlocks and rw semaphores.
4 *
5 * Based in part on code from semaphore.h and
6 * spinlock.h Copyright 1996 Linus Torvalds.
7 *
8 * Copyright 1999 Red Hat, Inc.
9 *
10 * Written by Benjamin LaHaise.
11 *
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.
16 */
17 #ifndef _ASM_I386_RWLOCK_H
18 #define _ASM_I386_RWLOCK_H
19
20 #define RW_LOCK_BIAS 0x01000000
21 #define RW_LOCK_BIAS_STR "0x01000000"
22
23 #define __build_read_lock_ptr(rw, helper) \
24 asm volatile(LOCK "subl $1,(%0)\n\t" \
25 "js 2f\n" \
26 "1:\n" \
27 ".section .text.lock,\"ax\"\n" \
28 "2:\tcall " helper "\n\t" \
29 "jmp 1b\n" \
30 ".previous" \
31 ::"a" (rw) : "memory")
32
33 #define __build_read_lock_const(rw, helper) \
34 asm volatile(LOCK "subl $1,%0\n\t" \
35 "js 2f\n" \
36 "1:\n" \
37 ".section .text.lock,\"ax\"\n" \
38 "2:\tpushl %%eax\n\t" \
39 "leal %0,%%eax\n\t" \
40 "call " helper "\n\t" \
41 "popl %%eax\n\t" \
42 "jmp 1b\n" \
43 ".previous" \
44 :"=m" (*(volatile int *)rw) : : "memory")
45
46 #define __build_read_lock(rw, helper) do { \
47 if (__builtin_constant_p(rw)) \
48 __build_read_lock_const(rw, helper); \
49 else \
50 __build_read_lock_ptr(rw, helper); \
51 } while (0)
52
53 #define __build_write_lock_ptr(rw, helper) \
54 asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
55 "jnz 2f\n" \
56 "1:\n" \
57 ".section .text.lock,\"ax\"\n" \
58 "2:\tcall " helper "\n\t" \
59 "jmp 1b\n" \
60 ".previous" \
61 ::"a" (rw) : "memory")
62
63 #define __build_write_lock_const(rw, helper) \
64 asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
65 "jnz 2f\n" \
66 "1:\n" \
67 ".section .text.lock,\"ax\"\n" \
68 "2:\tpushl %%eax\n\t" \
69 "leal %0,%%eax\n\t" \
70 "call " helper "\n\t" \
71 "popl %%eax\n\t" \
72 "jmp 1b\n" \
73 ".previous" \
74 :"=m" (*(volatile int *)rw) : : "memory")
75
76 #define __build_write_lock(rw, helper) do { \
77 if (__builtin_constant_p(rw)) \
78 __build_write_lock_const(rw, helper); \
79 else \
80 __build_write_lock_ptr(rw, helper); \
81 } while (0)
82
83 #endif
84
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