File: /usr/src/linux/include/asm-sh/semaphore-helper.h

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      */
17     static __inline__ void wake_one_more(struct semaphore * sem)
18     {
19     	atomic_inc((atomic_t *)&sem->sleepers);
20     }
21     
22     static __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      */
46     static __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      */
73     static __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 */
90