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1 | #ifndef _X86_64_SEMAPHORE_H |
2 | #define _X86_64_SEMAPHORE_H | |
3 | ||
4 | #include <linux/linkage.h> | |
5 | ||
6 | #ifdef __KERNEL__ | |
7 | ||
8 | /* | |
9 | * SMP- and interrupt-safe semaphores.. | |
10 | * | |
11 | * (C) Copyright 1996 Linus Torvalds | |
12 | * | |
13 | * Modified 1996-12-23 by Dave Grothe <dave@gcom.com> to fix bugs in | |
14 | * the original code and to make semaphore waits | |
15 | * interruptible so that processes waiting on | |
16 | * semaphores can be killed. | |
17 | * Modified 1999-02-14 by Andrea Arcangeli, split the sched.c helper | |
18 | * functions in asm/sempahore-helper.h while fixing a | |
19 | * potential and subtle race discovered by Ulrich Schmid | |
20 | * in down_interruptible(). Since I started to play here I | |
21 | * also implemented the `trylock' semaphore operation. | |
22 | * 1999-07-02 Artur Skawina <skawina@geocities.com> | |
23 | * Optimized "0(ecx)" -> "(ecx)" (the assembler does not | |
24 | * do this). Changed calling sequences from push/jmp to | |
25 | * traditional call/ret. | |
26 | * Modified 2001-01-01 Andreas Franck <afranck@gmx.de> | |
27 | * Some hacks to ensure compatibility with recent | |
28 | * GCC snapshots, to avoid stack corruption when compiling | |
29 | * with -fomit-frame-pointer. It's not sure if this will | |
30 | * be fixed in GCC, as our previous implementation was a | |
31 | * bit dubious. | |
32 | * | |
33 | * If you would like to see an analysis of this implementation, please | |
34 | * ftp to gcom.com and download the file | |
35 | * /pub/linux/src/semaphore/semaphore-2.0.24.tar.gz. | |
36 | * | |
37 | */ | |
38 | ||
39 | #include <asm/system.h> | |
40 | #include <asm/atomic.h> | |
41 | #include <asm/rwlock.h> | |
42 | #include <linux/wait.h> | |
43 | #include <linux/rwsem.h> | |
44 | #include <linux/stringify.h> | |
45 | ||
46 | struct semaphore { | |
47 | atomic_t count; | |
48 | int sleepers; | |
49 | wait_queue_head_t wait; | |
50 | }; | |
51 | ||
52 | #define __SEMAPHORE_INITIALIZER(name, n) \ | |
53 | { \ | |
54 | .count = ATOMIC_INIT(n), \ | |
55 | .sleepers = 0, \ | |
56 | .wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \ | |
57 | } | |
58 | ||
59 | #define __MUTEX_INITIALIZER(name) \ | |
60 | __SEMAPHORE_INITIALIZER(name,1) | |
61 | ||
62 | #define __DECLARE_SEMAPHORE_GENERIC(name,count) \ | |
63 | struct semaphore name = __SEMAPHORE_INITIALIZER(name,count) | |
64 | ||
65 | #define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1) | |
66 | #define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0) | |
67 | ||
68 | static inline void sema_init (struct semaphore *sem, int val) | |
69 | { | |
70 | /* | |
71 | * *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val); | |
72 | * | |
73 | * i'd rather use the more flexible initialization above, but sadly | |
74 | * GCC 2.7.2.3 emits a bogus warning. EGCS doesn't. Oh well. | |
75 | */ | |
76 | atomic_set(&sem->count, val); | |
77 | sem->sleepers = 0; | |
78 | init_waitqueue_head(&sem->wait); | |
79 | } | |
80 | ||
81 | static inline void init_MUTEX (struct semaphore *sem) | |
82 | { | |
83 | sema_init(sem, 1); | |
84 | } | |
85 | ||
86 | static inline void init_MUTEX_LOCKED (struct semaphore *sem) | |
87 | { | |
88 | sema_init(sem, 0); | |
89 | } | |
90 | ||
91 | asmlinkage void __down_failed(void /* special register calling convention */); | |
92 | asmlinkage int __down_failed_interruptible(void /* params in registers */); | |
93 | asmlinkage int __down_failed_trylock(void /* params in registers */); | |
94 | asmlinkage void __up_wakeup(void /* special register calling convention */); | |
95 | ||
96 | asmlinkage void __down(struct semaphore * sem); | |
97 | asmlinkage int __down_interruptible(struct semaphore * sem); | |
98 | asmlinkage int __down_trylock(struct semaphore * sem); | |
99 | asmlinkage void __up(struct semaphore * sem); | |
100 | ||
101 | /* | |
102 | * This is ugly, but we want the default case to fall through. | |
103 | * "__down_failed" is a special asm handler that calls the C | |
104 | * routine that actually waits. See arch/x86_64/kernel/semaphore.c | |
105 | */ | |
106 | static inline void down(struct semaphore * sem) | |
107 | { | |
108 | might_sleep(); | |
109 | ||
110 | __asm__ __volatile__( | |
111 | "# atomic down operation\n\t" | |
112 | LOCK "decl %0\n\t" /* --sem->count */ | |
113 | "js 2f\n" | |
114 | "1:\n" | |
115 | LOCK_SECTION_START("") | |
116 | "2:\tcall __down_failed\n\t" | |
117 | "jmp 1b\n" | |
118 | LOCK_SECTION_END | |
119 | :"=m" (sem->count) | |
120 | :"D" (sem) | |
121 | :"memory"); | |
122 | } | |
123 | ||
124 | /* | |
125 | * Interruptible try to acquire a semaphore. If we obtained | |
126 | * it, return zero. If we were interrupted, returns -EINTR | |
127 | */ | |
128 | static inline int down_interruptible(struct semaphore * sem) | |
129 | { | |
130 | int result; | |
131 | ||
132 | might_sleep(); | |
133 | ||
134 | __asm__ __volatile__( | |
135 | "# atomic interruptible down operation\n\t" | |
136 | LOCK "decl %1\n\t" /* --sem->count */ | |
137 | "js 2f\n\t" | |
138 | "xorl %0,%0\n" | |
139 | "1:\n" | |
140 | LOCK_SECTION_START("") | |
141 | "2:\tcall __down_failed_interruptible\n\t" | |
142 | "jmp 1b\n" | |
143 | LOCK_SECTION_END | |
144 | :"=a" (result), "=m" (sem->count) | |
145 | :"D" (sem) | |
146 | :"memory"); | |
147 | return result; | |
148 | } | |
149 | ||
150 | /* | |
151 | * Non-blockingly attempt to down() a semaphore. | |
152 | * Returns zero if we acquired it | |
153 | */ | |
154 | static inline int down_trylock(struct semaphore * sem) | |
155 | { | |
156 | int result; | |
157 | ||
158 | __asm__ __volatile__( | |
159 | "# atomic interruptible down operation\n\t" | |
160 | LOCK "decl %1\n\t" /* --sem->count */ | |
161 | "js 2f\n\t" | |
162 | "xorl %0,%0\n" | |
163 | "1:\n" | |
164 | LOCK_SECTION_START("") | |
165 | "2:\tcall __down_failed_trylock\n\t" | |
166 | "jmp 1b\n" | |
167 | LOCK_SECTION_END | |
168 | :"=a" (result), "=m" (sem->count) | |
169 | :"D" (sem) | |
170 | :"memory","cc"); | |
171 | return result; | |
172 | } | |
173 | ||
174 | /* | |
175 | * Note! This is subtle. We jump to wake people up only if | |
176 | * the semaphore was negative (== somebody was waiting on it). | |
177 | * The default case (no contention) will result in NO | |
178 | * jumps for both down() and up(). | |
179 | */ | |
180 | static inline void up(struct semaphore * sem) | |
181 | { | |
182 | __asm__ __volatile__( | |
183 | "# atomic up operation\n\t" | |
184 | LOCK "incl %0\n\t" /* ++sem->count */ | |
185 | "jle 2f\n" | |
186 | "1:\n" | |
187 | LOCK_SECTION_START("") | |
188 | "2:\tcall __up_wakeup\n\t" | |
189 | "jmp 1b\n" | |
190 | LOCK_SECTION_END | |
191 | :"=m" (sem->count) | |
192 | :"D" (sem) | |
193 | :"memory"); | |
194 | } | |
195 | #endif /* __KERNEL__ */ | |
196 | #endif |