Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * include/asm-ppc/rwsem.h: R/W semaphores for SH using the stuff |
| 3 | * in lib/rwsem.c. |
| 4 | */ |
| 5 | |
| 6 | #ifndef _ASM_SH_RWSEM_H |
| 7 | #define _ASM_SH_RWSEM_H |
| 8 | |
| 9 | #ifdef __KERNEL__ |
| 10 | #include <linux/list.h> |
| 11 | #include <linux/spinlock.h> |
| 12 | #include <asm/atomic.h> |
| 13 | #include <asm/system.h> |
| 14 | |
| 15 | /* |
| 16 | * the semaphore definition |
| 17 | */ |
| 18 | struct rw_semaphore { |
| 19 | long count; |
| 20 | #define RWSEM_UNLOCKED_VALUE 0x00000000 |
| 21 | #define RWSEM_ACTIVE_BIAS 0x00000001 |
| 22 | #define RWSEM_ACTIVE_MASK 0x0000ffff |
| 23 | #define RWSEM_WAITING_BIAS (-0x00010000) |
| 24 | #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS |
| 25 | #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS) |
| 26 | spinlock_t wait_lock; |
| 27 | struct list_head wait_list; |
| 28 | #if RWSEM_DEBUG |
| 29 | int debug; |
| 30 | #endif |
| 31 | }; |
| 32 | |
| 33 | /* |
| 34 | * initialisation |
| 35 | */ |
| 36 | #if RWSEM_DEBUG |
| 37 | #define __RWSEM_DEBUG_INIT , 0 |
| 38 | #else |
| 39 | #define __RWSEM_DEBUG_INIT /* */ |
| 40 | #endif |
| 41 | |
| 42 | #define __RWSEM_INITIALIZER(name) \ |
| 43 | { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \ |
| 44 | LIST_HEAD_INIT((name).wait_list) \ |
| 45 | __RWSEM_DEBUG_INIT } |
| 46 | |
| 47 | #define DECLARE_RWSEM(name) \ |
| 48 | struct rw_semaphore name = __RWSEM_INITIALIZER(name) |
| 49 | |
| 50 | extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem); |
| 51 | extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem); |
| 52 | extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem); |
| 53 | extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem); |
| 54 | |
| 55 | static inline void init_rwsem(struct rw_semaphore *sem) |
| 56 | { |
| 57 | sem->count = RWSEM_UNLOCKED_VALUE; |
| 58 | spin_lock_init(&sem->wait_lock); |
| 59 | INIT_LIST_HEAD(&sem->wait_list); |
| 60 | #if RWSEM_DEBUG |
| 61 | sem->debug = 0; |
| 62 | #endif |
| 63 | } |
| 64 | |
| 65 | /* |
| 66 | * lock for reading |
| 67 | */ |
| 68 | static inline void __down_read(struct rw_semaphore *sem) |
| 69 | { |
| 70 | if (atomic_inc_return((atomic_t *)(&sem->count)) > 0) |
| 71 | smp_wmb(); |
| 72 | else |
| 73 | rwsem_down_read_failed(sem); |
| 74 | } |
| 75 | |
| 76 | static inline int __down_read_trylock(struct rw_semaphore *sem) |
| 77 | { |
| 78 | int tmp; |
| 79 | |
| 80 | while ((tmp = sem->count) >= 0) { |
| 81 | if (tmp == cmpxchg(&sem->count, tmp, |
| 82 | tmp + RWSEM_ACTIVE_READ_BIAS)) { |
| 83 | smp_wmb(); |
| 84 | return 1; |
| 85 | } |
| 86 | } |
| 87 | return 0; |
| 88 | } |
| 89 | |
| 90 | /* |
| 91 | * lock for writing |
| 92 | */ |
| 93 | static inline void __down_write(struct rw_semaphore *sem) |
| 94 | { |
| 95 | int tmp; |
| 96 | |
| 97 | tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS, |
| 98 | (atomic_t *)(&sem->count)); |
| 99 | if (tmp == RWSEM_ACTIVE_WRITE_BIAS) |
| 100 | smp_wmb(); |
| 101 | else |
| 102 | rwsem_down_write_failed(sem); |
| 103 | } |
| 104 | |
| 105 | static inline int __down_write_trylock(struct rw_semaphore *sem) |
| 106 | { |
| 107 | int tmp; |
| 108 | |
| 109 | tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE, |
| 110 | RWSEM_ACTIVE_WRITE_BIAS); |
| 111 | smp_wmb(); |
| 112 | return tmp == RWSEM_UNLOCKED_VALUE; |
| 113 | } |
| 114 | |
| 115 | /* |
| 116 | * unlock after reading |
| 117 | */ |
| 118 | static inline void __up_read(struct rw_semaphore *sem) |
| 119 | { |
| 120 | int tmp; |
| 121 | |
| 122 | smp_wmb(); |
| 123 | tmp = atomic_dec_return((atomic_t *)(&sem->count)); |
| 124 | if (tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0) |
| 125 | rwsem_wake(sem); |
| 126 | } |
| 127 | |
| 128 | /* |
| 129 | * unlock after writing |
| 130 | */ |
| 131 | static inline void __up_write(struct rw_semaphore *sem) |
| 132 | { |
| 133 | smp_wmb(); |
| 134 | if (atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS, |
| 135 | (atomic_t *)(&sem->count)) < 0) |
| 136 | rwsem_wake(sem); |
| 137 | } |
| 138 | |
| 139 | /* |
| 140 | * implement atomic add functionality |
| 141 | */ |
| 142 | static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem) |
| 143 | { |
| 144 | atomic_add(delta, (atomic_t *)(&sem->count)); |
| 145 | } |
| 146 | |
| 147 | /* |
| 148 | * downgrade write lock to read lock |
| 149 | */ |
| 150 | static inline void __downgrade_write(struct rw_semaphore *sem) |
| 151 | { |
| 152 | int tmp; |
| 153 | |
| 154 | smp_wmb(); |
| 155 | tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count)); |
| 156 | if (tmp < 0) |
| 157 | rwsem_downgrade_wake(sem); |
| 158 | } |
| 159 | |
| 160 | /* |
| 161 | * implement exchange and add functionality |
| 162 | */ |
| 163 | static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem) |
| 164 | { |
| 165 | smp_mb(); |
| 166 | return atomic_add_return(delta, (atomic_t *)(&sem->count)); |
| 167 | } |
| 168 | |
Rik Van Riel | eb92f4e | 2005-10-29 18:15:44 -0700 | [diff] [blame^] | 169 | static inline int rwsem_is_locked(struct rw_semaphore *sem) |
| 170 | { |
| 171 | return (sem->count != 0); |
| 172 | } |
| 173 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 174 | #endif /* __KERNEL__ */ |
| 175 | #endif /* _ASM_SH_RWSEM_H */ |