aboutsummaryrefslogtreecommitdiffstats
path: root/include/asm-sh/spinlock.h
blob: 2586eef07d57214ec977f50b818d61c1c0fff9ed (plain) (blame)
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
/*
 * include/asm-sh/spinlock.h
 *
 * Copyright (C) 2002, 2003 Paul Mundt
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 */
#ifndef __ASM_SH_SPINLOCK_H
#define __ASM_SH_SPINLOCK_H

#include <asm/atomic.h>

/*
 * Your basic SMP spinlocks, allowing only a single CPU anywhere
 */

#define __raw_spin_is_locked(x)	((x)->lock != 0)
#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
#define __raw_spin_unlock_wait(x) \
	do { cpu_relax(); } while (__raw_spin_is_locked(x))

/*
 * Simple spin lock operations.  There are two variants, one clears IRQ's
 * on the local processor, one does not.
 *
 * We make no fairness assumptions.  They have a cost.
 */
static inline void __raw_spin_lock(raw_spinlock_t *lock)
{
	__asm__ __volatile__ (
		"1:\n\t"
		"tas.b @%0\n\t"
		"bf/s 1b\n\t"
		"nop\n\t"
		: "=r" (lock->lock)
		: "r" (&lock->lock)
		: "t", "memory"
	);
}

static inline void __raw_spin_unlock(raw_spinlock_t *lock)
{
	assert_spin_locked(lock);

	lock->lock = 0;
}

#define __raw_spin_trylock(x) (!test_and_set_bit(0, &(x)->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.
 */

static inline void __raw_read_lock(raw_rwlock_t *rw)
{
	__raw_spin_lock(&rw->lock);

	atomic_inc(&rw->counter);

	__raw_spin_unlock(&rw->lock);
}

static inline void __raw_read_unlock(raw_rwlock_t *rw)
{
	__raw_spin_lock(&rw->lock);

	atomic_dec(&rw->counter);

	__raw_spin_unlock(&rw->lock);
}

static inline void __raw_write_lock(raw_rwlock_t *rw)
{
	__raw_spin_lock(&rw->lock);
	atomic_set(&rw->counter, -1);
}

static inline void __raw_write_unlock(raw_rwlock_t *rw)
{
	atomic_set(&rw->counter, 0);
	__raw_spin_unlock(&rw->lock);
}

static inline int __raw_read_trylock(raw_rwlock_t *lock)
{
	atomic_t *count = (atomic_t*)lock;
	if (atomic_dec_return(count) >= 0)
		return 1;
	atomic_inc(count);
	return 0;
}

static inline int __raw_write_trylock(raw_rwlock_t *rw)
{
	if (atomic_sub_and_test(RW_LOCK_BIAS, &rw->counter))
		return 1;
	
	atomic_add(RW_LOCK_BIAS, &rw->counter);

	return 0;
}

#define _raw_spin_relax(lock)	cpu_relax()
#define _raw_read_relax(lock)	cpu_relax()
#define _raw_write_relax(lock)	cpu_relax()

#endif /* __ASM_SH_SPINLOCK_H */