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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-sh
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-sh')
-rw-r--r--include/asm-sh/semaphore-helper.h89
-rw-r--r--include/asm-sh/semaphore.h116
2 files changed, 1 insertions, 204 deletions
diff --git a/include/asm-sh/semaphore-helper.h b/include/asm-sh/semaphore-helper.h
deleted file mode 100644
index bd8230c369ca..000000000000
--- a/include/asm-sh/semaphore-helper.h
+++ /dev/null
@@ -1,89 +0,0 @@
1#ifndef __ASM_SH_SEMAPHORE_HELPER_H
2#define __ASM_SH_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->sleepers);
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->sleepers > 0) {
29 sem->sleepers--;
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->sleepers > 0) {
54 sem->sleepers--;
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->sleepers <= 0)
80 atomic_inc(&sem->count);
81 else {
82 sem->sleepers--;
83 ret = 0;
84 }
85 spin_unlock_irqrestore(&semaphore_wake_lock, flags);
86 return ret;
87}
88
89#endif /* __ASM_SH_SEMAPHORE_HELPER_H */
diff --git a/include/asm-sh/semaphore.h b/include/asm-sh/semaphore.h
index 9e5a37c4dce2..d9b2034ed1d2 100644
--- a/include/asm-sh/semaphore.h
+++ b/include/asm-sh/semaphore.h
@@ -1,115 +1 @@
1#ifndef __ASM_SH_SEMAPHORE_H #include <linux/semaphore.h>
2#define __ASM_SH_SEMAPHORE_H
3
4#include <linux/linkage.h>
5
6#ifdef __KERNEL__
7/*
8 * SMP- and interrupt-safe semaphores.
9 *
10 * (C) Copyright 1996 Linus Torvalds
11 *
12 * SuperH verison by Niibe Yutaka
13 * (Currently no asm implementation but generic C code...)
14 */
15
16#include <linux/spinlock.h>
17#include <linux/rwsem.h>
18#include <linux/wait.h>
19
20#include <asm/system.h>
21#include <asm/atomic.h>
22
23struct semaphore {
24 atomic_t count;
25 int sleepers;
26 wait_queue_head_t wait;
27};
28
29#define __SEMAPHORE_INITIALIZER(name, n) \
30{ \
31 .count = ATOMIC_INIT(n), \
32 .sleepers = 0, \
33 .wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
34}
35
36#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
37 struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
38
39#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
40
41static inline void sema_init (struct semaphore *sem, int val)
42{
43/*
44 * *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
45 *
46 * i'd rather use the more flexible initialization above, but sadly
47 * GCC 2.7.2.3 emits a bogus warning. EGCS doesn't. Oh well.
48 */
49 atomic_set(&sem->count, val);
50 sem->sleepers = 0;
51 init_waitqueue_head(&sem->wait);
52}
53
54static inline void init_MUTEX (struct semaphore *sem)
55{
56 sema_init(sem, 1);
57}
58
59static inline void init_MUTEX_LOCKED (struct semaphore *sem)
60{
61 sema_init(sem, 0);
62}
63
64#if 0
65asmlinkage void __down_failed(void /* special register calling convention */);
66asmlinkage int __down_failed_interruptible(void /* params in registers */);
67asmlinkage int __down_failed_trylock(void /* params in registers */);
68asmlinkage void __up_wakeup(void /* special register calling convention */);
69#endif
70
71asmlinkage void __down(struct semaphore * sem);
72asmlinkage int __down_interruptible(struct semaphore * sem);
73asmlinkage int __down_trylock(struct semaphore * sem);
74asmlinkage void __up(struct semaphore * sem);
75
76extern spinlock_t semaphore_wake_lock;
77
78static inline void down(struct semaphore * sem)
79{
80 might_sleep();
81 if (atomic_dec_return(&sem->count) < 0)
82 __down(sem);
83}
84
85static inline int down_interruptible(struct semaphore * sem)
86{
87 int ret = 0;
88
89 might_sleep();
90 if (atomic_dec_return(&sem->count) < 0)
91 ret = __down_interruptible(sem);
92 return ret;
93}
94
95static inline int down_trylock(struct semaphore * sem)
96{
97 int ret = 0;
98
99 if (atomic_dec_return(&sem->count) < 0)
100 ret = __down_trylock(sem);
101 return ret;
102}
103
104/*
105 * Note! This is subtle. We jump to wake people up only if
106 * the semaphore was negative (== somebody was waiting on it).
107 */
108static inline void up(struct semaphore * sem)
109{
110 if (atomic_inc_return(&sem->count) <= 0)
111 __up(sem);
112}
113
114#endif
115#endif /* __ASM_SH_SEMAPHORE_H */
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