1 #ifndef _I386_SEMAPHORE_H
2 #define _I386_SEMAPHORE_H
4 #include <linux/linkage.h>
9 * SMP- and interrupt-safe semaphores..
11 * (C) Copyright 1996 Linus Torvalds
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
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.
39 #include <asm/system.h>
40 #include <asm/atomic.h>
41 #include <linux/wait.h>
42 #include <linux/rwsem.h>
47 wait_queue_head_t wait
;
51 #define __SEMAPHORE_INITIALIZER(name, n) \
53 .count = ATOMIC_INIT(n), \
55 .wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
58 #define __MUTEX_INITIALIZER(name) \
59 __SEMAPHORE_INITIALIZER(name,1)
61 #define __DECLARE_SEMAPHORE_GENERIC(name,count) \
62 struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
64 #define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
65 #define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)
67 static inline void sema_init (struct semaphore
*sem
, int val
)
70 * *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
72 * i'd rather use the more flexible initialization above, but sadly
73 * GCC 2.7.2.3 emits a bogus warning. EGCS doesn't. Oh well.
75 atomic_set(&sem
->count
, val
);
77 init_waitqueue_head(&sem
->wait
);
80 static inline void init_MUTEX (struct semaphore
*sem
)
85 static inline void init_MUTEX_LOCKED (struct semaphore
*sem
)
90 fastcall
void __down_failed(void /* special register calling convention */);
91 fastcall
int __down_failed_interruptible(void /* params in registers */);
92 fastcall
int __down_failed_trylock(void /* params in registers */);
93 fastcall
void __up_wakeup(void /* special register calling convention */);
96 * This is ugly, but we want the default case to fall through.
97 * "__down_failed" is a special asm handler that calls the C
98 * routine that actually waits. See arch/i386/kernel/semaphore.c
100 static inline void down(struct semaphore
* sem
)
103 __asm__
__volatile__(
104 "# atomic down operation\n\t"
105 LOCK
"decl %0\n\t" /* --sem->count */
108 LOCK_SECTION_START("")
109 "2:\tlea %0,%%eax\n\t"
110 "call __down_failed\n\t"
119 * Interruptible try to acquire a semaphore. If we obtained
120 * it, return zero. If we were interrupted, returns -EINTR
122 static inline int down_interruptible(struct semaphore
* sem
)
127 __asm__
__volatile__(
128 "# atomic interruptible down operation\n\t"
129 LOCK
"decl %1\n\t" /* --sem->count */
133 LOCK_SECTION_START("")
134 "2:\tlea %1,%%eax\n\t"
135 "call __down_failed_interruptible\n\t"
138 :"=a" (result
), "=m" (sem
->count
)
145 * Non-blockingly attempt to down() a semaphore.
146 * Returns zero if we acquired it
148 static inline int down_trylock(struct semaphore
* sem
)
152 __asm__
__volatile__(
153 "# atomic interruptible down operation\n\t"
154 LOCK
"decl %1\n\t" /* --sem->count */
158 LOCK_SECTION_START("")
159 "2:\tlea %1,%%eax\n\t"
160 "call __down_failed_trylock\n\t"
163 :"=a" (result
), "=m" (sem
->count
)
170 * Note! This is subtle. We jump to wake people up only if
171 * the semaphore was negative (== somebody was waiting on it).
172 * The default case (no contention) will result in NO
173 * jumps for both down() and up().
175 static inline void up(struct semaphore
* sem
)
177 __asm__
__volatile__(
178 "# atomic up operation\n\t"
179 LOCK
"incl %0\n\t" /* ++sem->count */
182 LOCK_SECTION_START("")
183 "2:\tlea %0,%%eax\n\t"
184 "call __up_wakeup\n\t"