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1da177e4 LT |
1 | /* include/asm-x86_64/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 | * Copyright 2001,2002 SuSE labs | |
10 | * | |
11 | * Written by Benjamin LaHaise. | |
12 | * | |
13 | * This program is free software; you can redistribute it and/or | |
14 | * modify it under the terms of the GNU General Public License | |
15 | * as published by the Free Software Foundation; either version | |
16 | * 2 of the License, or (at your option) any later version. | |
17 | */ | |
18 | #ifndef _ASM_X86_64_RWLOCK_H | |
19 | #define _ASM_X86_64_RWLOCK_H | |
20 | ||
21 | #include <linux/stringify.h> | |
22 | ||
23 | #define RW_LOCK_BIAS 0x01000000 | |
24 | #define RW_LOCK_BIAS_STR "0x01000000" | |
25 | ||
26 | #define __build_read_lock_ptr(rw, helper) \ | |
27 | asm volatile(LOCK "subl $1,(%0)\n\t" \ | |
28 | "js 2f\n" \ | |
29 | "1:\n" \ | |
30 | LOCK_SECTION_START("") \ | |
31 | "2:\tcall " helper "\n\t" \ | |
32 | "jmp 1b\n" \ | |
33 | LOCK_SECTION_END \ | |
34 | ::"a" (rw) : "memory") | |
35 | ||
36 | #define __build_read_lock_const(rw, helper) \ | |
37 | asm volatile(LOCK "subl $1,%0\n\t" \ | |
38 | "js 2f\n" \ | |
39 | "1:\n" \ | |
40 | LOCK_SECTION_START("") \ | |
41 | "2:\tpushq %%rax\n\t" \ | |
42 | "leaq %0,%%rax\n\t" \ | |
43 | "call " helper "\n\t" \ | |
44 | "popq %%rax\n\t" \ | |
45 | "jmp 1b\n" \ | |
46 | LOCK_SECTION_END \ | |
47 | :"=m" (*((volatile int *)rw))::"memory") | |
48 | ||
49 | #define __build_read_lock(rw, helper) do { \ | |
50 | if (__builtin_constant_p(rw)) \ | |
51 | __build_read_lock_const(rw, helper); \ | |
52 | else \ | |
53 | __build_read_lock_ptr(rw, helper); \ | |
54 | } while (0) | |
55 | ||
56 | #define __build_write_lock_ptr(rw, helper) \ | |
57 | asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \ | |
58 | "jnz 2f\n" \ | |
59 | "1:\n" \ | |
60 | LOCK_SECTION_START("") \ | |
61 | "2:\tcall " helper "\n\t" \ | |
62 | "jmp 1b\n" \ | |
63 | LOCK_SECTION_END \ | |
64 | ::"a" (rw) : "memory") | |
65 | ||
66 | #define __build_write_lock_const(rw, helper) \ | |
67 | asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \ | |
68 | "jnz 2f\n" \ | |
69 | "1:\n" \ | |
70 | LOCK_SECTION_START("") \ | |
71 | "2:\tpushq %%rax\n\t" \ | |
72 | "leaq %0,%%rax\n\t" \ | |
73 | "call " helper "\n\t" \ | |
74 | "popq %%rax\n\t" \ | |
75 | "jmp 1b\n" \ | |
76 | LOCK_SECTION_END \ | |
77 | :"=m" (*((volatile long *)rw))::"memory") | |
78 | ||
79 | #define __build_write_lock(rw, helper) do { \ | |
80 | if (__builtin_constant_p(rw)) \ | |
81 | __build_write_lock_const(rw, helper); \ | |
82 | else \ | |
83 | __build_write_lock_ptr(rw, helper); \ | |
84 | } while (0) | |
85 | ||
86 | #endif |