[PATCH] s390: spin lock retry
[linux-2.6.git] / include / asm-s390 / spinlock.h
1 /*
2  *  include/asm-s390/spinlock.h
3  *
4  *  S390 version
5  *    Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
6  *    Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
7  *
8  *  Derived from "include/asm-i386/spinlock.h"
9  */
10
11 #ifndef __ASM_SPINLOCK_H
12 #define __ASM_SPINLOCK_H
13
14 static inline int
15 _raw_compare_and_swap(volatile unsigned int *lock,
16                       unsigned int old, unsigned int new)
17 {
18         asm volatile ("cs %0,%3,0(%4)"
19                       : "=d" (old), "=m" (*lock)
20                       : "0" (old), "d" (new), "a" (lock), "m" (*lock)
21                       : "cc", "memory" );
22         return old;
23 }
24
25 /*
26  * Simple spin lock operations.  There are two variants, one clears IRQ's
27  * on the local processor, one does not.
28  *
29  * We make no fairness assumptions. They have a cost.
30  */
31
32 typedef struct {
33         volatile unsigned int lock;
34 #ifdef CONFIG_PREEMPT
35         unsigned int break_lock;
36 #endif
37 } __attribute__ ((aligned (4))) spinlock_t;
38
39 #define SPIN_LOCK_UNLOCKED      (spinlock_t) { 0 }
40 #define spin_lock_init(lp)      do { (lp)->lock = 0; } while(0)
41 #define spin_unlock_wait(lp)    do { barrier(); } while(((volatile spinlock_t *)(lp))->lock)
42 #define spin_is_locked(x)       ((x)->lock != 0)
43 #define _raw_spin_lock_flags(lock, flags) _raw_spin_lock(lock)
44
45 extern void _raw_spin_lock_wait(spinlock_t *lp, unsigned int pc);
46 extern int _raw_spin_trylock_retry(spinlock_t *lp, unsigned int pc);
47
48 static inline void _raw_spin_lock(spinlock_t *lp)
49 {
50         unsigned long pc = (unsigned long) __builtin_return_address(0);
51
52         if (unlikely(_raw_compare_and_swap(&lp->lock, 0, pc) != 0))
53                 _raw_spin_lock_wait(lp, pc);
54 }
55
56 static inline int _raw_spin_trylock(spinlock_t *lp)
57 {
58         unsigned long pc = (unsigned long) __builtin_return_address(0);
59
60         if (likely(_raw_compare_and_swap(&lp->lock, 0, pc) == 0))
61                 return 1;
62         return _raw_spin_trylock_retry(lp, pc);
63 }
64
65 static inline void _raw_spin_unlock(spinlock_t *lp)
66 {
67         _raw_compare_and_swap(&lp->lock, lp->lock, 0);
68 }
69                 
70 /*
71  * Read-write spinlocks, allowing multiple readers
72  * but only one writer.
73  *
74  * NOTE! it is quite common to have readers in interrupts
75  * but no interrupt writers. For those circumstances we
76  * can "mix" irq-safe locks - any writer needs to get a
77  * irq-safe write-lock, but readers can get non-irqsafe
78  * read-locks.
79  */
80 typedef struct {
81         volatile unsigned int lock;
82         volatile unsigned long owner_pc;
83 #ifdef CONFIG_PREEMPT
84         unsigned int break_lock;
85 #endif
86 } rwlock_t;
87
88 #define RW_LOCK_UNLOCKED (rwlock_t) { 0, 0 }
89
90 #define rwlock_init(x)  do { *(x) = RW_LOCK_UNLOCKED; } while(0)
91
92 /**
93  * read_can_lock - would read_trylock() succeed?
94  * @lock: the rwlock in question.
95  */
96 #define read_can_lock(x) ((int)(x)->lock >= 0)
97
98 /**
99  * write_can_lock - would write_trylock() succeed?
100  * @lock: the rwlock in question.
101  */
102 #define write_can_lock(x) ((x)->lock == 0)
103
104 extern void _raw_read_lock_wait(rwlock_t *lp);
105 extern int _raw_read_trylock_retry(rwlock_t *lp);
106 extern void _raw_write_lock_wait(rwlock_t *lp);
107 extern int _raw_write_trylock_retry(rwlock_t *lp);
108
109 static inline void _raw_read_lock(rwlock_t *rw)
110 {
111         unsigned int old;
112         old = rw->lock & 0x7fffffffU;
113         if (_raw_compare_and_swap(&rw->lock, old, old + 1) != old)
114                 _raw_read_lock_wait(rw);
115 }
116
117 static inline void _raw_read_unlock(rwlock_t *rw)
118 {
119         unsigned int old, cmp;
120
121         old = rw->lock;
122         do {
123                 cmp = old;
124                 old = _raw_compare_and_swap(&rw->lock, old, old - 1);
125         } while (cmp != old);
126 }
127
128 static inline void _raw_write_lock(rwlock_t *rw)
129 {
130         if (unlikely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) != 0))
131                 _raw_write_lock_wait(rw);
132 }
133
134 static inline void _raw_write_unlock(rwlock_t *rw)
135 {
136         _raw_compare_and_swap(&rw->lock, 0x80000000, 0);
137 }
138
139 static inline int _raw_read_trylock(rwlock_t *rw)
140 {
141         unsigned int old;
142         old = rw->lock & 0x7fffffffU;
143         if (likely(_raw_compare_and_swap(&rw->lock, old, old + 1) == old))
144                 return 1;
145         return _raw_read_trylock_retry(rw);
146 }
147
148 static inline int _raw_write_trylock(rwlock_t *rw)
149 {
150         if (likely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0))
151                 return 1;
152         return _raw_write_trylock_retry(rw);
153 }
154
155 #endif /* __ASM_SPINLOCK_H */