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Linux/arch/mn10300/include/asm/spinlock.h

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  1 /* MN10300 spinlock support
  2  *
  3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
  4  * Written by David Howells (dhowells@redhat.com)
  5  *
  6  * This program is free software; you can redistribute it and/or
  7  * modify it under the terms of the GNU General Public Licence
  8  * as published by the Free Software Foundation; either version
  9  * 2 of the Licence, or (at your option) any later version.
 10  */
 11 #ifndef _ASM_SPINLOCK_H
 12 #define _ASM_SPINLOCK_H
 13 
 14 #include <linux/atomic.h>
 15 #include <asm/rwlock.h>
 16 #include <asm/page.h>
 17 
 18 /*
 19  * Simple spin lock operations.  There are two variants, one clears IRQ's
 20  * on the local processor, one does not.
 21  *
 22  * We make no fairness assumptions. They have a cost.
 23  */
 24 
 25 #define arch_spin_is_locked(x)  (*(volatile signed char *)(&(x)->slock) != 0)
 26 #define arch_spin_unlock_wait(x) do { barrier(); } while (arch_spin_is_locked(x))
 27 
 28 static inline void arch_spin_unlock(arch_spinlock_t *lock)
 29 {
 30         asm volatile(
 31                 "       bclr    1,(0,%0)        \n"
 32                 :
 33                 : "a"(&lock->slock)
 34                 : "memory", "cc");
 35 }
 36 
 37 static inline int arch_spin_trylock(arch_spinlock_t *lock)
 38 {
 39         int ret;
 40 
 41         asm volatile(
 42                 "       mov     1,%0            \n"
 43                 "       bset    %0,(%1)         \n"
 44                 "       bne     1f              \n"
 45                 "       clr     %0              \n"
 46                 "1:     xor     1,%0            \n"
 47                 : "=d"(ret)
 48                 : "a"(&lock->slock)
 49                 : "memory", "cc");
 50 
 51         return ret;
 52 }
 53 
 54 static inline void arch_spin_lock(arch_spinlock_t *lock)
 55 {
 56         asm volatile(
 57                 "1:     bset    1,(0,%0)        \n"
 58                 "       bne     1b              \n"
 59                 :
 60                 : "a"(&lock->slock)
 61                 : "memory", "cc");
 62 }
 63 
 64 static inline void arch_spin_lock_flags(arch_spinlock_t *lock,
 65                                          unsigned long flags)
 66 {
 67         int temp;
 68 
 69         asm volatile(
 70                 "1:     bset    1,(0,%2)        \n"
 71                 "       beq     3f              \n"
 72                 "       mov     %1,epsw         \n"
 73                 "2:     mov     (0,%2),%0       \n"
 74                 "       or      %0,%0           \n"
 75                 "       bne     2b              \n"
 76                 "       mov     %3,%0           \n"
 77                 "       mov     %0,epsw         \n"
 78                 "       nop                     \n"
 79                 "       nop                     \n"
 80                 "       bra     1b\n"
 81                 "3:                             \n"
 82                 : "=&d" (temp)
 83                 : "d" (flags), "a"(&lock->slock), "i"(EPSW_IE | MN10300_CLI_LEVEL)
 84                 : "memory", "cc");
 85 }
 86 
 87 #ifdef __KERNEL__
 88 
 89 /*
 90  * Read-write spinlocks, allowing multiple readers
 91  * but only one writer.
 92  *
 93  * NOTE! it is quite common to have readers in interrupts
 94  * but no interrupt writers. For those circumstances we
 95  * can "mix" irq-safe locks - any writer needs to get a
 96  * irq-safe write-lock, but readers can get non-irqsafe
 97  * read-locks.
 98  */
 99 
100 /**
101  * read_can_lock - would read_trylock() succeed?
102  * @lock: the rwlock in question.
103  */
104 #define arch_read_can_lock(x) ((int)(x)->lock > 0)
105 
106 /**
107  * write_can_lock - would write_trylock() succeed?
108  * @lock: the rwlock in question.
109  */
110 #define arch_write_can_lock(x) ((x)->lock == RW_LOCK_BIAS)
111 
112 /*
113  * On mn10300, we implement read-write locks as a 32-bit counter
114  * with the high bit (sign) being the "contended" bit.
115  */
116 static inline void arch_read_lock(arch_rwlock_t *rw)
117 {
118 #if 0 //def CONFIG_MN10300_HAS_ATOMIC_OPS_UNIT
119         __build_read_lock(rw, "__read_lock_failed");
120 #else
121         {
122                 atomic_t *count = (atomic_t *)rw;
123                 while (atomic_dec_return(count) < 0)
124                         atomic_inc(count);
125         }
126 #endif
127 }
128 
129 static inline void arch_write_lock(arch_rwlock_t *rw)
130 {
131 #if 0 //def CONFIG_MN10300_HAS_ATOMIC_OPS_UNIT
132         __build_write_lock(rw, "__write_lock_failed");
133 #else
134         {
135                 atomic_t *count = (atomic_t *)rw;
136                 while (!atomic_sub_and_test(RW_LOCK_BIAS, count))
137                         atomic_add(RW_LOCK_BIAS, count);
138         }
139 #endif
140 }
141 
142 static inline void arch_read_unlock(arch_rwlock_t *rw)
143 {
144 #if 0 //def CONFIG_MN10300_HAS_ATOMIC_OPS_UNIT
145         __build_read_unlock(rw);
146 #else
147         {
148                 atomic_t *count = (atomic_t *)rw;
149                 atomic_inc(count);
150         }
151 #endif
152 }
153 
154 static inline void arch_write_unlock(arch_rwlock_t *rw)
155 {
156 #if 0 //def CONFIG_MN10300_HAS_ATOMIC_OPS_UNIT
157         __build_write_unlock(rw);
158 #else
159         {
160                 atomic_t *count = (atomic_t *)rw;
161                 atomic_add(RW_LOCK_BIAS, count);
162         }
163 #endif
164 }
165 
166 static inline int arch_read_trylock(arch_rwlock_t *lock)
167 {
168         atomic_t *count = (atomic_t *)lock;
169         atomic_dec(count);
170         if (atomic_read(count) >= 0)
171                 return 1;
172         atomic_inc(count);
173         return 0;
174 }
175 
176 static inline int arch_write_trylock(arch_rwlock_t *lock)
177 {
178         atomic_t *count = (atomic_t *)lock;
179         if (atomic_sub_and_test(RW_LOCK_BIAS, count))
180                 return 1;
181         atomic_add(RW_LOCK_BIAS, count);
182         return 0;
183 }
184 
185 #define arch_read_lock_flags(lock, flags)  arch_read_lock(lock)
186 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
187 
188 #define _raw_spin_relax(lock)   cpu_relax()
189 #define _raw_read_relax(lock)   cpu_relax()
190 #define _raw_write_relax(lock)  cpu_relax()
191 
192 #endif /* __KERNEL__ */
193 #endif /* _ASM_SPINLOCK_H */
194 

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