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;
  29         sem->count += 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 = sem->count;
  56         do {
  57                 new = res + RWSEM_ACTIVE_READ_BIAS;
  58                 if (new <= 0)
  59                         break;
  60                 old = res;
  61                 res = cmpxchg(&sem->count, old, new);
  62         } while (res != old);
  63         return res >= 0 ? 1 : 0;
  64 }
  65
  66 static inline void __down_write(struct rw_semaphore *sem)
  67 {
  68         long oldcount;
  69 #ifndef CONFIG_SMP
  70         oldcount = sem->count;
  71         sem->count += 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         if (unlikely(oldcount))
  87                 rwsem_down_write_failed(sem);
  88 }
  89
  90 /*
  91  * trylock for writing -- returns 1 if successful, 0 if contention
  92  */
  93 static inline int __down_write_trylock(struct rw_semaphore *sem)
  94 {
  95         long ret = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
  96                            RWSEM_ACTIVE_WRITE_BIAS);
  97         if (ret == RWSEM_UNLOCKED_VALUE)
  98                 return 1;
  99         return 0;
 100 }
 101
 102 static inline void __up_read(struct rw_semaphore *sem)
 103 {
 104         long oldcount;
 105 #ifndef CONFIG_SMP
 106         oldcount = sem->count;
 107         sem->count -= RWSEM_ACTIVE_READ_BIAS;
 108 #else
 109         long temp;
 110         __asm__ __volatile__(
 111         "       mb\n"
 112         "1:     ldq_l   %0,%1\n"
 113         "       subq    %0,%3,%2\n"
 114         "       stq_c   %2,%1\n"
 115         "       beq     %2,2f\n"
 116         ".subsection 2\n"
 117         "2:     br      1b\n"
 118         ".previous"
 119         :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
 120         :"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory");
 121 #endif
 122         if (unlikely(oldcount < 0))
 123                 if ((int)oldcount - RWSEM_ACTIVE_READ_BIAS == 0)
 124                         rwsem_wake(sem);
 125 }
 126
 127 static inline void __up_write(struct rw_semaphore *sem)
 128 {
 129         long count;
 130 #ifndef CONFIG_SMP
 131         sem->count -= RWSEM_ACTIVE_WRITE_BIAS;
 132         count = sem->count;
 133 #else
 134         long temp;
 135         __asm__ __volatile__(
 136         "       mb\n"
 137         "1:     ldq_l   %0,%1\n"
 138         "       subq    %0,%3,%2\n"
 139         "       stq_c   %2,%1\n"
 140         "       beq     %2,2f\n"
 141         "       subq    %0,%3,%0\n"
 142         ".subsection 2\n"
 143         "2:     br      1b\n"
 144         ".previous"
 145         :"=&r" (count), "=m" (sem->count), "=&r" (temp)
 146         :"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");
 147 #endif
 148         if (unlikely(count))
 149                 if ((int)count == 0)
 150                         rwsem_wake(sem);
 151 }
 152
 153 /*
 154  * downgrade write lock to read lock
 155  */
 156 static inline void __downgrade_write(struct rw_semaphore *sem)
 157 {
 158         long oldcount;
 159 #ifndef CONFIG_SMP
 160         oldcount = sem->count;
 161         sem->count -= RWSEM_WAITING_BIAS;
 162 #else
 163         long temp;
 164         __asm__ __volatile__(
 165         "1:     ldq_l   %0,%1\n"
 166         "       addq    %0,%3,%2\n"
 167         "       stq_c   %2,%1\n"
 168         "       beq     %2,2f\n"
 169         "       mb\n"
 170         ".subsection 2\n"
 171         "2:     br      1b\n"
 172         ".previous"
 173         :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
 174         :"Ir" (-RWSEM_WAITING_BIAS), "m" (sem->count) : "memory");
 175 #endif
 176         if (unlikely(oldcount < 0))
 177                 rwsem_downgrade_wake(sem);
 178 }
 179
 180 static inline void rwsem_atomic_add(long val, struct rw_semaphore *sem)
 181 {
 182 #ifndef CONFIG_SMP
 183         sem->count += val;
 184 #else
 185         long temp;
 186         __asm__ __volatile__(
 187         "1:     ldq_l   %0,%1\n"
 188         "       addq    %0,%2,%0\n"
 189         "       stq_c   %0,%1\n"
 190         "       beq     %0,2f\n"
 191         ".subsection 2\n"
 192         "2:     br      1b\n"
 193         ".previous"
 194         :"=&r" (temp), "=m" (sem->count)
 195         :"Ir" (val), "m" (sem->count));
 196 #endif
 197 }
 198
 199 static inline long rwsem_atomic_update(long val, struct rw_semaphore *sem)
 200 {
 201 #ifndef CONFIG_SMP
 202         sem->count += val;
 203         return sem->count;
 204 #else
 205         long ret, temp;
 206         __asm__ __volatile__(
 207         "1:     ldq_l   %0,%1\n"
 208         "       addq    %0,%3,%2\n"
 209         "       addq    %0,%3,%0\n"
 210         "       stq_c   %2,%1\n"
 211         "       beq     %2,2f\n"
 212         ".subsection 2\n"
 213         "2:     br      1b\n"
 214         ".previous"
 215         :"=&r" (ret), "=m" (sem->count), "=&r" (temp)
 216         :"Ir" (val), "m" (sem->count));
 217
 218         return ret;
 219 #endif
 220 }
 221
 222 #endif /* __KERNEL__ */
 223 #endif /* _ALPHA_RWSEM_H */