include/asm-arm/semaphore.h

   1 /*
   2  * linux/include/asm-arm/semaphore.h
   3  */
   4 #ifndef __ASM_ARM_SEMAPHORE_H
   5 #define __ASM_ARM_SEMAPHORE_H
   6
   7 #include <linux/linkage.h>
   8 #include <linux/spinlock.h>
   9 #include <linux/wait.h>
  10
  11 #include <asm/atomic.h>
  12 #include <asm/proc/locks.h>
  13
  14 struct semaphore {
  15         atomic_t count;
  16         int sleepers;
  17         wait_queue_head_t wait;
  18 #if WAITQUEUE_DEBUG
  19         long __magic;
  20 #endif
  21 };
  22
  23 #if WAITQUEUE_DEBUG
  24 # define __SEM_DEBUG_INIT(name) \
  25                 , (long)&(name).__magic
  26 #else
  27 # define __SEM_DEBUG_INIT(name)
  28 #endif
  29
  30 #define __SEMAPHORE_INIT(name,count)                    \
  31         { ATOMIC_INIT(count), 0,                        \
  32           __WAIT_QUEUE_HEAD_INITIALIZER((name).wait)    \
  33           __SEM_DEBUG_INIT(name) }
  34
  35 #define __MUTEX_INITIALIZER(name) \
  36         __SEMAPHORE_INIT(name,1)
  37
  38 #define __DECLARE_SEMAPHORE_GENERIC(name,count) \
  39         struct semaphore name = __SEMAPHORE_INIT(name,count)
  40
  41 #define DECLARE_MUTEX(name)             __DECLARE_SEMAPHORE_GENERIC(name,1)
  42 #define DECLARE_MUTEX_LOCKED(name)      __DECLARE_SEMAPHORE_GENERIC(name,0)
  43
  44 extern inline void sema_init(struct semaphore *sem, int val)
  45 {
  46         atomic_set(&sem->count, val);
  47         sem->sleepers = 0;
  48         init_waitqueue_head(&sem->wait);
  49 #if WAITQUEUE_DEBUG
  50         sem->__magic = (long)&sem->__magic;
  51 #endif
  52 }
  53
  54 static inline void init_MUTEX(struct semaphore *sem)
  55 {
  56         sema_init(sem, 1);
  57 }
  58
  59 static inline void init_MUTEX_LOCKED(struct semaphore *sem)
  60 {
  61         sema_init(sem, 0);
  62 }
  63
  64 /*
  65  * special register calling convention
  66  */
  67 asmlinkage void __down_failed(void);
  68 asmlinkage int  __down_interruptible_failed(void);
  69 asmlinkage int  __down_trylock_failed(void);
  70 asmlinkage void __up_wakeup(void);
  71
  72 extern void __down(struct semaphore * sem);
  73 extern int  __down_interruptible(struct semaphore * sem);
  74 extern int  __down_trylock(struct semaphore * sem);
  75 extern void __up(struct semaphore * sem);
  76
  77 /*
  78  * This is ugly, but we want the default case to fall through.
  79  * "__down" is the actual routine that waits...
  80  */
  81 extern inline void down(struct semaphore * sem)
  82 {
  83 #if WAITQUEUE_DEBUG
  84         CHECK_MAGIC(sem->__magic);
  85 #endif
  86
  87         __down_op(sem, __down_failed);
  88 }
  89
  90 /*
  91  * This is ugly, but we want the default case to fall through.
  92  * "__down_interruptible" is the actual routine that waits...
  93  */
  94 extern inline int down_interruptible (struct semaphore * sem)
  95 {
  96 #if WAITQUEUE_DEBUG
  97         CHECK_MAGIC(sem->__magic);
  98 #endif
  99
 100         return __down_op_ret(sem, __down_interruptible_failed);
 101 }
 102
 103 extern inline int down_trylock(struct semaphore *sem)
 104 {
 105 #if WAITQUEUE_DEBUG
 106         CHECK_MAGIC(sem->__magic);
 107 #endif
 108
 109         return __down_op_ret(sem, __down_trylock_failed);
 110 }
 111
 112 /*
 113  * Note! This is subtle. We jump to wake people up only if
 114  * the semaphore was negative (== somebody was waiting on it).
 115  * The default case (no contention) will result in NO
 116  * jumps for both down() and up().
 117  */
 118 extern inline void up(struct semaphore * sem)
 119 {
 120 #if WAITQUEUE_DEBUG
 121         CHECK_MAGIC(sem->__magic);
 122 #endif
 123
 124         __up_op(sem, __up_wakeup);
 125 }
 126
 127 /* rw mutexes (should that be mutices? =) -- throw rw
 128  * spinlocks and semaphores together, and this is what we
 129  * end up with...
 130  *
 131  * The lock is initialized to BIAS.  This way, a writer
 132  * subtracts BIAS ands gets 0 for the case of an uncontended
 133  * lock.  Readers decrement by 1 and see a positive value
 134  * when uncontended, negative if there are writers waiting
 135  * (in which case it goes to sleep).
 136  *
 137  * In terms of fairness, this should result in the lock
 138  * flopping back and forth between readers and writers
 139  * under heavy use.
 140  *
 141  *              -ben
 142  */
 143 struct rw_semaphore {
 144         atomic_t                count;
 145         volatile unsigned char  write_bias_granted;
 146         volatile unsigned char  read_bias_granted;
 147         volatile unsigned char  pad1;
 148         volatile unsigned char  pad2;
 149         wait_queue_head_t       wait;
 150         wait_queue_head_t       write_bias_wait;
 151 #if WAITQUEUE_DEBUG
 152         long                    __magic;
 153         atomic_t                readers;
 154         atomic_t                writers;
 155 #endif
 156 };
 157
 158 #if WAITQUEUE_DEBUG
 159 #define __RWSEM_DEBUG_INIT      , ATOMIC_INIT(0), ATOMIC_INIT(0)
 160 #else
 161 #define __RWSEM_DEBUG_INIT      /* */
 162 #endif
 163
 164 #define __RWSEM_INITIALIZER(name,count) \
 165 { ATOMIC_INIT(count), 0, 0, 0, 0, __WAIT_QUEUE_HEAD_INITIALIZER((name).wait), \
 166         __WAIT_QUEUE_HEAD_INITIALIZER((name).write_bias_wait) \
 167         __SEM_DEBUG_INIT(name) __RWSEM_DEBUG_INIT }
 168
 169 #define __DECLARE_RWSEM_GENERIC(name,count) \
 170         struct rw_semaphore name = __RWSEM_INITIALIZER(name,count)
 171
 172 #define DECLARE_RWSEM(name) __DECLARE_RWSEM_GENERIC(name,RW_LOCK_BIAS)
 173 #define DECLARE_RWSEM_READ_LOCKED(name) __DECLARE_RWSEM_GENERIC(name,RW_LOCK_BIAS-1)
 174 #define DECLARE_RWSEM_WRITE_LOCKED(name) __DECLARE_RWSEM_GENERIC(name,0)
 175
 176 extern inline void init_rwsem(struct rw_semaphore *sem)
 177 {
 178         atomic_set(&sem->count, RW_LOCK_BIAS);
 179         sem->read_bias_granted = 0;
 180         sem->write_bias_granted = 0;
 181         init_waitqueue_head(&sem->wait);
 182         init_waitqueue_head(&sem->write_bias_wait);
 183 #if WAITQUEUE_DEBUG
 184         sem->__magic = (long)&sem->__magic;
 185         atomic_set(&sem->readers, 0);
 186         atomic_set(&sem->writers, 0);
 187 #endif
 188 }
 189
 190 extern struct rw_semaphore *__down_read_failed(struct rw_semaphore *sem);
 191 extern struct rw_semaphore *__down_write_failed(struct rw_semaphore *sem);
 192 extern struct rw_semaphore *__rwsem_wake(struct rw_semaphore *sem);
 193
 194 extern inline void down_read(struct rw_semaphore *sem)
 195 {
 196 #if WAITQUEUE_DEBUG
 197         CHECK_MAGIC(sem->__magic);
 198 #endif
 199         __down_op_read(sem, __down_read_failed);
 200 #if WAITQUEUE_DEBUG
 201         if (sem->write_bias_granted)
 202                 BUG();
 203         if (atomic_read(&sem->writers))
 204                 BUG();
 205         atomic_inc(&sem->readers);
 206 #endif
 207 }
 208
 209 extern inline void down_write(struct rw_semaphore *sem)
 210 {
 211 #if WAITQUEUE_DEBUG
 212         CHECK_MAGIC(sem->__magic);
 213 #endif
 214         __down_op_write(sem, __down_write_failed);
 215 #if WAITQUEUE_DEBUG
 216         if (atomic_read(&sem->writers))
 217                 BUG();
 218         if (atomic_read(&sem->readers))
 219                 BUG();
 220         if (sem->read_bias_granted)
 221                 BUG();
 222         if (sem->write_bias_granted)
 223                 BUG();
 224         atomic_inc(&sem->writers);
 225 #endif
 226 }
 227
 228 extern inline void up_read(struct rw_semaphore *sem)
 229 {
 230 #if WAITQUEUE_DEBUG
 231         if (sem->write_bias_granted)
 232                 BUG();
 233         if (atomic_read(&sem->writers))
 234                 BUG();
 235         atomic_dec(&sem->readers);
 236 #endif
 237         __up_op_read(sem, __rwsem_wake);
 238 }
 239
 240 extern inline void up_write(struct rw_semaphore *sem)
 241 {
 242 #if WAITQUEUE_DEBUG
 243         if (sem->read_bias_granted)
 244                 BUG();
 245         if (sem->write_bias_granted)
 246                 BUG();
 247         if (atomic_read(&sem->readers))
 248                 BUG();
 249         if (atomic_read(&sem->writers) != 1)
 250                 BUG();
 251         atomic_dec(&sem->writers);
 252 #endif
 253         __up_op_write(sem, __rwsem_wake);
 254 }
 255
 256 #endif