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   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 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  29         struct lockdep_map      dep_map;
  30 #endif
  31 };
  32
  33 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  34 # define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
  35 #else
  36 # define __RWSEM_DEP_MAP_INIT(lockname)
  37 #endif
  38
  39 #define __RWSEM_INITIALIZER(name) \
  40         { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \
  41           LIST_HEAD_INIT((name).wait_list) \
  42           __RWSEM_DEP_MAP_INIT(name) }
  43
  44 #define DECLARE_RWSEM(name)             \
  45         struct rw_semaphore name = __RWSEM_INITIALIZER(name)
  46
  47 extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
  48 extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
  49 extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
  50 extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
  51
  52 extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
  53                          struct lock_class_key *key);
  54
  55 #define init_rwsem(sem)                         \
  56 do {                                            \
  57         static struct lock_class_key __key;     \
  58                                                 \
  59         __init_rwsem((sem), #sem, &__key);      \
  60 } while (0)
  61
  62 static inline void init_rwsem(struct rw_semaphore *sem)
  63 {
  64         sem->count = RWSEM_UNLOCKED_VALUE;
  65         spin_lock_init(&sem->wait_lock);
  66         INIT_LIST_HEAD(&sem->wait_list);
  67 }
  68
  69 /*
  70  * lock for reading
  71  */
  72 static inline void __down_read(struct rw_semaphore *sem)
  73 {
  74         if (atomic_inc_return((atomic_t *)(&sem->count)) > 0)
  75                 smp_wmb();
  76         else
  77                 rwsem_down_read_failed(sem);
  78 }
  79
  80 static inline int __down_read_trylock(struct rw_semaphore *sem)
  81 {
  82         int tmp;
  83
  84         while ((tmp = sem->count) >= 0) {
  85                 if (tmp == cmpxchg(&sem->count, tmp,
  86                                    tmp + RWSEM_ACTIVE_READ_BIAS)) {
  87                         smp_wmb();
  88                         return 1;
  89                 }
  90         }
  91         return 0;
  92 }
  93
  94 /*
  95  * lock for writing
  96  */
  97 static inline void __down_write(struct rw_semaphore *sem)
  98 {
  99         int tmp;
 100
 101         tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS,
 102                                 (atomic_t *)(&sem->count));
 103         if (tmp == RWSEM_ACTIVE_WRITE_BIAS)
 104                 smp_wmb();
 105         else
 106                 rwsem_down_write_failed(sem);
 107 }
 108
 109 static inline int __down_write_trylock(struct rw_semaphore *sem)
 110 {
 111         int tmp;
 112
 113         tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
 114                       RWSEM_ACTIVE_WRITE_BIAS);
 115         smp_wmb();
 116         return tmp == RWSEM_UNLOCKED_VALUE;
 117 }
 118
 119 /*
 120  * unlock after reading
 121  */
 122 static inline void __up_read(struct rw_semaphore *sem)
 123 {
 124         int tmp;
 125
 126         smp_wmb();
 127         tmp = atomic_dec_return((atomic_t *)(&sem->count));
 128         if (tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0)
 129                 rwsem_wake(sem);
 130 }
 131
 132 /*
 133  * unlock after writing
 134  */
 135 static inline void __up_write(struct rw_semaphore *sem)
 136 {
 137         smp_wmb();
 138         if (atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
 139                               (atomic_t *)(&sem->count)) < 0)
 140                 rwsem_wake(sem);
 141 }
 142
 143 /*
 144  * implement atomic add functionality
 145  */
 146 static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
 147 {
 148         atomic_add(delta, (atomic_t *)(&sem->count));
 149 }
 150
 151 /*
 152  * downgrade write lock to read lock
 153  */
 154 static inline void __downgrade_write(struct rw_semaphore *sem)
 155 {
 156         int tmp;
 157
 158         smp_wmb();
 159         tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count));
 160         if (tmp < 0)
 161                 rwsem_downgrade_wake(sem);
 162 }
 163
 164 static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
 165 {
 166         __down_write(sem);
 167 }
 168
 169 /*
 170  * implement exchange and add functionality
 171  */
 172 static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
 173 {
 174         smp_mb();
 175         return atomic_add_return(delta, (atomic_t *)(&sem->count));
 176 }
 177
 178 static inline int rwsem_is_locked(struct rw_semaphore *sem)
 179 {
 180         return (sem->count != 0);
 181 }
 182
 183 #endif /* __KERNEL__ */
 184 #endif /* _ASM_SH_RWSEM_H */