arch/alpha/include/asm/rwsem.h

   1 #ifndef _ALPHA_RWSEM_H
   2 #define _ALPHA_RWSEM_H
   3
   4 /*
   5  * Written by Ivan Kokshaysky <ink@jurassic.park.msu.ru>, 2001.
   6  * Based on asm-alpha/semaphore.h and asm-i386/rwsem.h
   7  */
   8
   9 #ifndef _LINUX_RWSEM_H
  10 #error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
  11 #endif
  12
  13 #ifdef __KERNEL__
  14
  15 #include <linux/compiler.h>
  16
  17 #define RWSEM_UNLOCKED_VALUE            0x0000000000000000L
  18 #define RWSEM_ACTIVE_BIAS               0x0000000000000001L
  19 #define RWSEM_ACTIVE_MASK               0x00000000ffffffffL
  20 #define RWSEM_WAITING_BIAS              (-0x0000000100000000L)
  21 #define RWSEM_ACTIVE_READ_BIAS          RWSEM_ACTIVE_BIAS
  22 #define RWSEM_ACTIVE_WRITE_BIAS         (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
  23
  24 static inline void __down_read(struct rw_semaphore *sem)
  25 {
  26         long oldcount;
  27 #ifndef CONFIG_SMP
  28         oldcount = sem->count.counter;
  29         sem->count.counter += RWSEM_ACTIVE_READ_BIAS;
  30 #else
  31         long temp;
  32         __asm__ __volatile__(
  33         "1:     ldq_l   %0,%1\n"
  34         "       addq    %0,%3,%2\n"
  35         "       stq_c   %2,%1\n"
  36         "       beq     %2,2f\n"
  37         "       mb\n"
  38         ".subsection 2\n"
  39         "2:     br      1b\n"
  40         ".previous"
  41         :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
  42         :"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory");
  43 #endif
  44         if (unlikely(oldcount < 0))
  45                 rwsem_down_read_failed(sem);
  46 }
  47
  48 /*
  49  * trylock for reading -- returns 1 if successful, 0 if contention
  50  */
  51 static inline int __down_read_trylock(struct rw_semaphore *sem)
  52 {
  53         long old, new, res;
  54
  55         res = atomic_long_read(&sem->count);
  56         do {
  57                 new = res + RWSEM_ACTIVE_READ_BIAS;
  58                 if (new <= 0)
  59                         break;
  60                 old = res;
  61                 res = atomic_long_cmpxchg(&sem->count, old, new);
  62         } while (res != old);
  63         return res >= 0 ? 1 : 0;
  64 }
  65
  66 static inline long ___down_write(struct rw_semaphore *sem)
  67 {
  68         long oldcount;
  69 #ifndef CONFIG_SMP
  70         oldcount = sem->count.counter;
  71         sem->count.counter += RWSEM_ACTIVE_WRITE_BIAS;
  72 #else
  73         long temp;
  74         __asm__ __volatile__(
  75         "1:     ldq_l   %0,%1\n"
  76         "       addq    %0,%3,%2\n"
  77         "       stq_c   %2,%1\n"
  78         "       beq     %2,2f\n"
  79         "       mb\n"
  80         ".subsection 2\n"
  81         "2:     br      1b\n"
  82         ".previous"
  83         :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
  84         :"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");
  85 #endif
  86         return oldcount;
  87 }
  88
  89 static inline void __down_write(struct rw_semaphore *sem)
  90 {
  91         if (unlikely(___down_write(sem)))
  92                 rwsem_down_write_failed(sem);
  93 }
  94
  95 static inline int __down_write_killable(struct rw_semaphore *sem)
  96 {
  97         if (unlikely(___down_write(sem)))
  98                 if (IS_ERR(rwsem_down_write_failed_killable(sem)))
  99                         return -EINTR;
 100
 101         return 0;
 102 }
 103
 104 /*
 105  * trylock for writing -- returns 1 if successful, 0 if contention
 106  */
 107 static inline int __down_write_trylock(struct rw_semaphore *sem)
 108 {
 109         long ret = atomic_long_cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
 110                            RWSEM_ACTIVE_WRITE_BIAS);
 111         if (ret == RWSEM_UNLOCKED_VALUE)
 112                 return 1;
 113         return 0;
 114 }
 115
 116 static inline void __up_read(struct rw_semaphore *sem)
 117 {
 118         long oldcount;
 119 #ifndef CONFIG_SMP
 120         oldcount = sem->count.counter;
 121         sem->count.counter -= RWSEM_ACTIVE_READ_BIAS;
 122 #else
 123         long temp;
 124         __asm__ __volatile__(
 125         "       mb\n"
 126         "1:     ldq_l   %0,%1\n"
 127         "       subq    %0,%3,%2\n"
 128         "       stq_c   %2,%1\n"
 129         "       beq     %2,2f\n"
 130         ".subsection 2\n"
 131         "2:     br      1b\n"
 132         ".previous"
 133         :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
 134         :"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory");
 135 #endif
 136         if (unlikely(oldcount < 0))
 137                 if ((int)oldcount - RWSEM_ACTIVE_READ_BIAS == 0)
 138                         rwsem_wake(sem);
 139 }
 140
 141 static inline void __up_write(struct rw_semaphore *sem)
 142 {
 143         long count;
 144 #ifndef CONFIG_SMP
 145         sem->count.counter -= RWSEM_ACTIVE_WRITE_BIAS;
 146         count = sem->count.counter;
 147 #else
 148         long temp;
 149         __asm__ __volatile__(
 150         "       mb\n"
 151         "1:     ldq_l   %0,%1\n"
 152         "       subq    %0,%3,%2\n"
 153         "       stq_c   %2,%1\n"
 154         "       beq     %2,2f\n"
 155         "       subq    %0,%3,%0\n"
 156         ".subsection 2\n"
 157         "2:     br      1b\n"
 158         ".previous"
 159         :"=&r" (count), "=m" (sem->count), "=&r" (temp)
 160         :"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");
 161 #endif
 162         if (unlikely(count))
 163                 if ((int)count == 0)
 164                         rwsem_wake(sem);
 165 }
 166
 167 /*
 168  * downgrade write lock to read lock
 169  */
 170 static inline void __downgrade_write(struct rw_semaphore *sem)
 171 {
 172         long oldcount;
 173 #ifndef CONFIG_SMP
 174         oldcount = sem->count.counter;
 175         sem->count.counter -= RWSEM_WAITING_BIAS;
 176 #else
 177         long temp;
 178         __asm__ __volatile__(
 179         "1:     ldq_l   %0,%1\n"
 180         "       addq    %0,%3,%2\n"
 181         "       stq_c   %2,%1\n"
 182         "       beq     %2,2f\n"
 183         "       mb\n"
 184         ".subsection 2\n"
 185         "2:     br      1b\n"
 186         ".previous"
 187         :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
 188         :"Ir" (-RWSEM_WAITING_BIAS), "m" (sem->count) : "memory");
 189 #endif
 190         if (unlikely(oldcount < 0))
 191                 rwsem_downgrade_wake(sem);
 192 }
 193
 194 #endif /* __KERNEL__ */
 195 #endif /* _ALPHA_RWSEM_H */