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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-cris
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-cris')
-rw-r--r--include/asm-cris/semaphore-helper.h78
-rw-r--r--include/asm-cris/semaphore.h134
2 files changed, 1 insertions, 211 deletions
diff --git a/include/asm-cris/semaphore-helper.h b/include/asm-cris/semaphore-helper.h
deleted file mode 100644
index 27bfeca1b981..000000000000
--- a/include/asm-cris/semaphore-helper.h
+++ /dev/null
@@ -1,78 +0,0 @@
1/* $Id: semaphore-helper.h,v 1.3 2001/03/26 15:00:33 orjanf Exp $
2 *
3 * SMP- and interrupt-safe semaphores helper functions. Generic versions, no
4 * optimizations whatsoever...
5 *
6 */
7
8#ifndef _ASM_SEMAPHORE_HELPER_H
9#define _ASM_SEMAPHORE_HELPER_H
10
11#include <asm/atomic.h>
12#include <linux/errno.h>
13
14#define read(a) ((a)->counter)
15#define inc(a) (((a)->counter)++)
16#define dec(a) (((a)->counter)--)
17
18#define count_inc(a) ((*(a))++)
19
20/*
21 * These two _must_ execute atomically wrt each other.
22 */
23static inline void wake_one_more(struct semaphore * sem)
24{
25 atomic_inc(&sem->waking);
26}
27
28static inline int waking_non_zero(struct semaphore *sem)
29{
30 unsigned long flags;
31 int ret = 0;
32
33 local_irq_save(flags);
34 if (read(&sem->waking) > 0) {
35 dec(&sem->waking);
36 ret = 1;
37 }
38 local_irq_restore(flags);
39 return ret;
40}
41
42static inline int waking_non_zero_interruptible(struct semaphore *sem,
43 struct task_struct *tsk)
44{
45 int ret = 0;
46 unsigned long flags;
47
48 local_irq_save(flags);
49 if (read(&sem->waking) > 0) {
50 dec(&sem->waking);
51 ret = 1;
52 } else if (signal_pending(tsk)) {
53 inc(&sem->count);
54 ret = -EINTR;
55 }
56 local_irq_restore(flags);
57 return ret;
58}
59
60static inline int waking_non_zero_trylock(struct semaphore *sem)
61{
62 int ret = 1;
63 unsigned long flags;
64
65 local_irq_save(flags);
66 if (read(&sem->waking) <= 0)
67 inc(&sem->count);
68 else {
69 dec(&sem->waking);
70 ret = 0;
71 }
72 local_irq_restore(flags);
73 return ret;
74}
75
76#endif /* _ASM_SEMAPHORE_HELPER_H */
77
78
diff --git a/include/asm-cris/semaphore.h b/include/asm-cris/semaphore.h
index 31a4ac448195..d9b2034ed1d2 100644
--- a/include/asm-cris/semaphore.h
+++ b/include/asm-cris/semaphore.h
@@ -1,133 +1 @@
1/* $Id: semaphore.h,v 1.3 2001/05/08 13:54:09 bjornw Exp $ */ #include <linux/semaphore.h>
2
3/* On the i386 these are coded in asm, perhaps we should as well. Later.. */
4
5#ifndef _CRIS_SEMAPHORE_H
6#define _CRIS_SEMAPHORE_H
7
8#define RW_LOCK_BIAS 0x01000000
9
10#include <linux/wait.h>
11#include <linux/spinlock.h>
12#include <linux/rwsem.h>
13
14#include <asm/system.h>
15#include <asm/atomic.h>
16
17/*
18 * CRIS semaphores, implemented in C-only so far.
19 */
20
21struct semaphore {
22 atomic_t count;
23 atomic_t waking;
24 wait_queue_head_t wait;
25};
26
27#define __SEMAPHORE_INITIALIZER(name, n) \
28{ \
29 .count = ATOMIC_INIT(n), \
30 .waking = ATOMIC_INIT(0), \
31 .wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
32}
33
34#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
35 struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
36
37#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
38
39static inline void sema_init(struct semaphore *sem, int val)
40{
41 *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
42}
43
44static inline void init_MUTEX (struct semaphore *sem)
45{
46 sema_init(sem, 1);
47}
48
49static inline void init_MUTEX_LOCKED (struct semaphore *sem)
50{
51 sema_init(sem, 0);
52}
53
54extern void __down(struct semaphore * sem);
55extern int __down_interruptible(struct semaphore * sem);
56extern int __down_trylock(struct semaphore * sem);
57extern void __up(struct semaphore * sem);
58
59/* notice - we probably can do cli/sti here instead of saving */
60
61static inline void down(struct semaphore * sem)
62{
63 unsigned long flags;
64 int failed;
65
66 might_sleep();
67
68 /* atomically decrement the semaphores count, and if its negative, we wait */
69 cris_atomic_save(sem, flags);
70 failed = --(sem->count.counter) < 0;
71 cris_atomic_restore(sem, flags);
72 if(failed) {
73 __down(sem);
74 }
75}
76
77/*
78 * This version waits in interruptible state so that the waiting
79 * process can be killed. The down_interruptible routine
80 * returns negative for signalled and zero for semaphore acquired.
81 */
82
83static inline int down_interruptible(struct semaphore * sem)
84{
85 unsigned long flags;
86 int failed;
87
88 might_sleep();
89
90 /* atomically decrement the semaphores count, and if its negative, we wait */
91 cris_atomic_save(sem, flags);
92 failed = --(sem->count.counter) < 0;
93 cris_atomic_restore(sem, flags);
94 if(failed)
95 failed = __down_interruptible(sem);
96 return(failed);
97}
98
99static inline int down_trylock(struct semaphore * sem)
100{
101 unsigned long flags;
102 int failed;
103
104 cris_atomic_save(sem, flags);
105 failed = --(sem->count.counter) < 0;
106 cris_atomic_restore(sem, flags);
107 if(failed)
108 failed = __down_trylock(sem);
109 return(failed);
110
111}
112
113/*
114 * Note! This is subtle. We jump to wake people up only if
115 * the semaphore was negative (== somebody was waiting on it).
116 * The default case (no contention) will result in NO
117 * jumps for both down() and up().
118 */
119static inline void up(struct semaphore * sem)
120{
121 unsigned long flags;
122 int wakeup;
123
124 /* atomically increment the semaphores count, and if it was negative, we wake people */
125 cris_atomic_save(sem, flags);
126 wakeup = ++(sem->count.counter) <= 0;
127 cris_atomic_restore(sem, flags);
128 if(wakeup) {
129 __up(sem);
130 }
131}
132
133#endif
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