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1/*
2 * include/asm-sh/spinlock.h
3 *
4 * Copyright (C) 2002, 2003 Paul Mundt
5 *
6 * This file is subject to the terms and conditions of the GNU General Public
7 * License. See the file "COPYING" in the main directory of this archive
8 * for more details.
9 */
10#ifndef __ASM_SH_SPINLOCK_H
11#define __ASM_SH_SPINLOCK_H
12
13#include <asm/atomic.h>
14
15/*
16 * Your basic SMP spinlocks, allowing only a single CPU anywhere
17 */
18typedef struct {
19 volatile unsigned long lock;
20#ifdef CONFIG_PREEMPT
21 unsigned int break_lock;
22#endif
23} spinlock_t;
24
25#define SPIN_LOCK_UNLOCKED (spinlock_t) { 0 }
26
27#define spin_lock_init(x) do { *(x) = SPIN_LOCK_UNLOCKED; } while(0)
28
29#define spin_is_locked(x) ((x)->lock != 0)
30#define spin_unlock_wait(x) do { barrier(); } while (spin_is_locked(x))
31#define _raw_spin_lock_flags(lock, flags) _raw_spin_lock(lock)
32
33/*
34 * Simple spin lock operations. There are two variants, one clears IRQ's
35 * on the local processor, one does not.
36 *
37 * We make no fairness assumptions. They have a cost.
38 */
39static inline void _raw_spin_lock(spinlock_t *lock)
40{
41 __asm__ __volatile__ (
42 "1:\n\t"
43 "tas.b @%0\n\t"
44 "bf/s 1b\n\t"
45 "nop\n\t"
46 : "=r" (lock->lock)
47 : "r" (&lock->lock)
48 : "t", "memory"
49 );
50}
51
52static inline void _raw_spin_unlock(spinlock_t *lock)
53{
54 assert_spin_locked(lock);
55
56 lock->lock = 0;
57}
58
59#define _raw_spin_trylock(x) (!test_and_set_bit(0, &(x)->lock))
60
61/*
62 * Read-write spinlocks, allowing multiple readers but only one writer.
63 *
64 * NOTE! it is quite common to have readers in interrupts but no interrupt
65 * writers. For those circumstances we can "mix" irq-safe locks - any writer
66 * needs to get a irq-safe write-lock, but readers can get non-irqsafe
67 * read-locks.
68 */
69typedef struct {
70 spinlock_t lock;
71 atomic_t counter;
72#ifdef CONFIG_PREEMPT
73 unsigned int break_lock;
74#endif
75} rwlock_t;
76
77#define RW_LOCK_BIAS 0x01000000
78#define RW_LOCK_UNLOCKED (rwlock_t) { { 0 }, { RW_LOCK_BIAS } }
79#define rwlock_init(x) do { *(x) = RW_LOCK_UNLOCKED; } while (0)
80
81static inline void _raw_read_lock(rwlock_t *rw)
82{
83 _raw_spin_lock(&rw->lock);
84
85 atomic_inc(&rw->counter);
86
87 _raw_spin_unlock(&rw->lock);
88}
89
90static inline void _raw_read_unlock(rwlock_t *rw)
91{
92 _raw_spin_lock(&rw->lock);
93
94 atomic_dec(&rw->counter);
95
96 _raw_spin_unlock(&rw->lock);
97}
98
99static inline void _raw_write_lock(rwlock_t *rw)
100{
101 _raw_spin_lock(&rw->lock);
102 atomic_set(&rw->counter, -1);
103}
104
105static inline void _raw_write_unlock(rwlock_t *rw)
106{
107 atomic_set(&rw->counter, 0);
108 _raw_spin_unlock(&rw->lock);
109}
110
111#define _raw_read_trylock(lock) generic_raw_read_trylock(lock)
112
113static inline int _raw_write_trylock(rwlock_t *rw)
114{
115 if (atomic_sub_and_test(RW_LOCK_BIAS, &rw->counter))
116 return 1;
117
118 atomic_add(RW_LOCK_BIAS, &rw->counter);
119
120 return 0;
121}
122
123#endif /* __ASM_SH_SPINLOCK_H */
124