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authorMatthew Wilcox <matthew@wil.cx>2008-03-07 21:55:58 -0500
committerMatthew Wilcox <willy@linux.intel.com>2008-04-17 10:42:34 -0400
commit64ac24e738823161693bf791f87adc802cf529ff (patch)
tree19c0b0cf314d4394ca580c05b86cdf874ce0a167 /include/asm-parisc
parente48b3deee475134585eed03e7afebe4bf9e0dba9 (diff)
Generic semaphore implementation
Semaphores are no longer performance-critical, so a generic C implementation is better for maintainability, debuggability and extensibility. Thanks to Peter Zijlstra for fixing the lockdep warning. Thanks to Harvey Harrison for pointing out that the unlikely() was unnecessary. Signed-off-by: Matthew Wilcox <willy@linux.intel.com> Acked-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include/asm-parisc')
-rw-r--r--include/asm-parisc/semaphore-helper.h89
-rw-r--r--include/asm-parisc/semaphore.h146
2 files changed, 1 insertions, 234 deletions
diff --git a/include/asm-parisc/semaphore-helper.h b/include/asm-parisc/semaphore-helper.h
deleted file mode 100644
index 387f7c1277a2..000000000000
--- a/include/asm-parisc/semaphore-helper.h
+++ /dev/null
@@ -1,89 +0,0 @@
1#ifndef _ASM_PARISC_SEMAPHORE_HELPER_H
2#define _ASM_PARISC_SEMAPHORE_HELPER_H
3
4/*
5 * SMP- and interrupt-safe semaphores helper functions.
6 *
7 * (C) Copyright 1996 Linus Torvalds
8 * (C) Copyright 1999 Andrea Arcangeli
9 */
10
11/*
12 * These two _must_ execute atomically wrt each other.
13 *
14 * This is trivially done with load_locked/store_cond,
15 * which we have. Let the rest of the losers suck eggs.
16 */
17static __inline__ void wake_one_more(struct semaphore * sem)
18{
19 atomic_inc((atomic_t *)&sem->waking);
20}
21
22static __inline__ int waking_non_zero(struct semaphore *sem)
23{
24 unsigned long flags;
25 int ret = 0;
26
27 spin_lock_irqsave(&semaphore_wake_lock, flags);
28 if (sem->waking > 0) {
29 sem->waking--;
30 ret = 1;
31 }
32 spin_unlock_irqrestore(&semaphore_wake_lock, flags);
33 return ret;
34}
35
36/*
37 * waking_non_zero_interruptible:
38 * 1 got the lock
39 * 0 go to sleep
40 * -EINTR interrupted
41 *
42 * We must undo the sem->count down_interruptible() increment while we are
43 * protected by the spinlock in order to make atomic this atomic_inc() with the
44 * atomic_read() in wake_one_more(), otherwise we can race. -arca
45 */
46static __inline__ int waking_non_zero_interruptible(struct semaphore *sem,
47 struct task_struct *tsk)
48{
49 unsigned long flags;
50 int ret = 0;
51
52 spin_lock_irqsave(&semaphore_wake_lock, flags);
53 if (sem->waking > 0) {
54 sem->waking--;
55 ret = 1;
56 } else if (signal_pending(tsk)) {
57 atomic_inc(&sem->count);
58 ret = -EINTR;
59 }
60 spin_unlock_irqrestore(&semaphore_wake_lock, flags);
61 return ret;
62}
63
64/*
65 * waking_non_zero_trylock:
66 * 1 failed to lock
67 * 0 got the lock
68 *
69 * We must undo the sem->count down_trylock() increment while we are
70 * protected by the spinlock in order to make atomic this atomic_inc() with the
71 * atomic_read() in wake_one_more(), otherwise we can race. -arca
72 */
73static __inline__ int waking_non_zero_trylock(struct semaphore *sem)
74{
75 unsigned long flags;
76 int ret = 1;
77
78 spin_lock_irqsave(&semaphore_wake_lock, flags);
79 if (sem->waking <= 0)
80 atomic_inc(&sem->count);
81 else {
82 sem->waking--;
83 ret = 0;
84 }
85 spin_unlock_irqrestore(&semaphore_wake_lock, flags);
86 return ret;
87}
88
89#endif /* _ASM_PARISC_SEMAPHORE_HELPER_H */
diff --git a/include/asm-parisc/semaphore.h b/include/asm-parisc/semaphore.h
index a16271cdc748..d9b2034ed1d2 100644
--- a/include/asm-parisc/semaphore.h
+++ b/include/asm-parisc/semaphore.h
@@ -1,145 +1 @@
1/* SMP- and interrupt-safe semaphores. #include <linux/semaphore.h>
2 * PA-RISC version by Matthew Wilcox
3 *
4 * Linux/PA-RISC Project (http://www.parisc-linux.org/)
5 * Copyright (C) 1996 Linus Torvalds
6 * Copyright (C) 1999-2001 Matthew Wilcox < willy at debian d0T org >
7 * Copyright (C) 2000 Grant Grundler < grundler a debian org >
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
13 *
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU General Public License for more details.
18 *
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
22 */
23
24#ifndef _ASM_PARISC_SEMAPHORE_H
25#define _ASM_PARISC_SEMAPHORE_H
26
27#include <linux/spinlock.h>
28#include <linux/wait.h>
29#include <linux/rwsem.h>
30
31#include <asm/system.h>
32
33/*
34 * The `count' is initialised to the number of people who are allowed to
35 * take the lock. (Normally we want a mutex, so this is `1'). if
36 * `count' is positive, the lock can be taken. if it's 0, no-one is
37 * waiting on it. if it's -1, at least one task is waiting.
38 */
39struct semaphore {
40 spinlock_t sentry;
41 int count;
42 wait_queue_head_t wait;
43};
44
45#define __SEMAPHORE_INITIALIZER(name, n) \
46{ \
47 .sentry = SPIN_LOCK_UNLOCKED, \
48 .count = n, \
49 .wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
50}
51
52#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
53 struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
54
55#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
56
57static inline void sema_init (struct semaphore *sem, int val)
58{
59 *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
60}
61
62static inline void init_MUTEX (struct semaphore *sem)
63{
64 sema_init(sem, 1);
65}
66
67static inline void init_MUTEX_LOCKED (struct semaphore *sem)
68{
69 sema_init(sem, 0);
70}
71
72static inline int sem_getcount(struct semaphore *sem)
73{
74 return sem->count;
75}
76
77asmlinkage void __down(struct semaphore * sem);
78asmlinkage int __down_interruptible(struct semaphore * sem);
79asmlinkage void __up(struct semaphore * sem);
80
81/* Semaphores can be `tried' from irq context. So we have to disable
82 * interrupts while we're messing with the semaphore. Sorry.
83 */
84
85static inline void down(struct semaphore * sem)
86{
87 might_sleep();
88 spin_lock_irq(&sem->sentry);
89 if (sem->count > 0) {
90 sem->count--;
91 } else {
92 __down(sem);
93 }
94 spin_unlock_irq(&sem->sentry);
95}
96
97static inline int down_interruptible(struct semaphore * sem)
98{
99 int ret = 0;
100 might_sleep();
101 spin_lock_irq(&sem->sentry);
102 if (sem->count > 0) {
103 sem->count--;
104 } else {
105 ret = __down_interruptible(sem);
106 }
107 spin_unlock_irq(&sem->sentry);
108 return ret;
109}
110
111/*
112 * down_trylock returns 0 on success, 1 if we failed to get the lock.
113 * May not sleep, but must preserve irq state
114 */
115static inline int down_trylock(struct semaphore * sem)
116{
117 unsigned long flags;
118 int count;
119
120 spin_lock_irqsave(&sem->sentry, flags);
121 count = sem->count - 1;
122 if (count >= 0)
123 sem->count = count;
124 spin_unlock_irqrestore(&sem->sentry, flags);
125 return (count < 0);
126}
127
128/*
129 * Note! This is subtle. We jump to wake people up only if
130 * the semaphore was negative (== somebody was waiting on it).
131 */
132static inline void up(struct semaphore * sem)
133{
134 unsigned long flags;
135
136 spin_lock_irqsave(&sem->sentry, flags);
137 if (sem->count < 0) {
138 __up(sem);
139 } else {
140 sem->count++;
141 }
142 spin_unlock_irqrestore(&sem->sentry, flags);
143}
144
145#endif /* _ASM_PARISC_SEMAPHORE_H */
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