summaryrefslogtreecommitdiff
path: root/include/asm-cris/arch-v32/spinlock.h
blob: 52df72a622329659d27524f57fc1d2f95556bc13 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
#ifndef __ASM_ARCH_SPINLOCK_H
#define __ASM_ARCH_SPINLOCK_H

#include <asm/system.h>

#define RW_LOCK_BIAS 0x01000000
#define SPIN_LOCK_UNLOCKED (spinlock_t) { 1 }
#define spin_lock_init(x)	do { *(x) = SPIN_LOCK_UNLOCKED; } while(0)

#define spin_is_locked(x)	(*(volatile signed char *)(&(x)->lock) <= 0)
#define spin_unlock_wait(x)	do { barrier(); } while(spin_is_locked(x))

extern void cris_spin_unlock(void *l, int val);
extern void cris_spin_lock(void *l);
extern int cris_spin_trylock(void* l);

static inline void _raw_spin_unlock(spinlock_t *lock)
{
	__asm__ volatile ("move.d %1,%0" \
	                  : "=m" (lock->lock) \
			  : "r" (1) \
			  : "memory");
}

static inline int _raw_spin_trylock(spinlock_t *lock)
{
	return cris_spin_trylock((void*)&lock->lock);
}

static inline void _raw_spin_lock(spinlock_t *lock)
{
	cris_spin_lock((void*)&lock->lock);
}

static inline void _raw_spin_lock_flags (spinlock_t *lock, unsigned long flags)
{
  _raw_spin_lock(lock);
}

/*
 * Read-write spinlocks, allowing multiple readers
 * but only one writer.
 *
 * NOTE! it is quite common to have readers in interrupts
 * but no interrupt writers. For those circumstances we
 * can "mix" irq-safe locks - any writer needs to get a
 * irq-safe write-lock, but readers can get non-irqsafe
 * read-locks.
 */
typedef struct {
	spinlock_t lock;
	volatile int counter;
#ifdef CONFIG_PREEMPT
	unsigned int break_lock;
#endif
} rwlock_t;

#define RW_LOCK_UNLOCKED (rwlock_t) { {1}, 0 }

#define rwlock_init(lp)	do { *(lp) = RW_LOCK_UNLOCKED; } while (0)

/**
 * read_can_lock - would read_trylock() succeed?
 * @lock: the rwlock in question.
 */
#define read_can_lock(x) ((int)(x)->counter >= 0)

/**
 * write_can_lock - would write_trylock() succeed?
 * @lock: the rwlock in question.
 */
#define write_can_lock(x) ((x)->counter == 0)

#define _raw_read_trylock(lock) generic_raw_read_trylock(lock)

/* read_lock, read_unlock are pretty straightforward.  Of course it somehow
 * sucks we end up saving/restoring flags twice for read_lock_irqsave aso. */

static  __inline__ void _raw_read_lock(rwlock_t *rw)
{
	unsigned long flags;
	local_irq_save(flags);
	_raw_spin_lock(&rw->lock);

	rw->counter++;

	_raw_spin_unlock(&rw->lock);
	local_irq_restore(flags);
}

static  __inline__ void _raw_read_unlock(rwlock_t *rw)
{
	unsigned long flags;
	local_irq_save(flags);
	_raw_spin_lock(&rw->lock);

	rw->counter--;

	_raw_spin_unlock(&rw->lock);
	local_irq_restore(flags);
}

/* write_lock is less trivial.  We optimistically grab the lock and check
 * if we surprised any readers.  If so we release the lock and wait till
 * they're all gone before trying again
 *
 * Also note that we don't use the _irqsave / _irqrestore suffixes here.
 * If we're called with interrupts enabled and we've got readers (or other
 * writers) in interrupt handlers someone fucked up and we'd dead-lock
 * sooner or later anyway.   prumpf */

static  __inline__ void _raw_write_lock(rwlock_t *rw)
{
retry:
	_raw_spin_lock(&rw->lock);

	if(rw->counter != 0) {
		/* this basically never happens */
		_raw_spin_unlock(&rw->lock);

		while(rw->counter != 0);

		goto retry;
	}

	/* got it.  now leave without unlocking */
	rw->counter = -1; /* remember we are locked */
}

/* write_unlock is absolutely trivial - we don't have to wait for anything */

static  __inline__ void _raw_write_unlock(rwlock_t *rw)
{
	rw->counter = 0;
	_raw_spin_unlock(&rw->lock);
}

static  __inline__ int _raw_write_trylock(rwlock_t *rw)
{
	_raw_spin_lock(&rw->lock);
	if (rw->counter != 0) {
		/* this basically never happens */
		_raw_spin_unlock(&rw->lock);

		return 0;
	}

	/* got it.  now leave without unlocking */
	rw->counter = -1; /* remember we are locked */
	return 1;
}

static __inline__ int is_read_locked(rwlock_t *rw)
{
	return rw->counter > 0;
}

static __inline__ int is_write_locked(rwlock_t *rw)
{
	return rw->counter < 0;
}

#endif /* __ASM_ARCH_SPINLOCK_H */