arch/alpha/include/asm/rwsem.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ALPHA_RWSEM_H
   3 #define _ALPHA_RWSEM_H
   4
   5 /*
   6  * Written by Ivan Kokshaysky <ink@jurassic.park.msu.ru>, 2001.
   7  * Based on asm-alpha/semaphore.h and asm-i386/rwsem.h
   8  */
   9
  10 #ifndef _LINUX_RWSEM_H
  11 #error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
  12 #endif
  13
  14 #ifdef __KERNEL__
  15
  16 #include <linux/compiler.h>
  17
  18 #define RWSEM_UNLOCKED_VALUE            0x0000000000000000L
  19 #define RWSEM_ACTIVE_BIAS               0x0000000000000001L
  20 #define RWSEM_ACTIVE_MASK               0x00000000ffffffffL
  21 #define RWSEM_WAITING_BIAS              (-0x0000000100000000L)
  22 #define RWSEM_ACTIVE_READ_BIAS          RWSEM_ACTIVE_BIAS
  23 #define RWSEM_ACTIVE_WRITE_BIAS         (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
  24
  25 static inline int ___down_read(struct rw_semaphore *sem)
  26 {
  27         long oldcount;
  28 #ifndef CONFIG_SMP
  29         oldcount = sem->count.counter;
  30         sem->count.counter += RWSEM_ACTIVE_READ_BIAS;
  31 #else
  32         long temp;
  33         __asm__ __volatile__(
  34         "1:     ldq_l   %0,%1\n"
  35         "       addq    %0,%3,%2\n"
  36         "       stq_c   %2,%1\n"
  37         "       beq     %2,2f\n"
  38         "       mb\n"
  39         ".subsection 2\n"
  40         "2:     br      1b\n"
  41         ".previous"
  42         :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
  43         :"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory");
  44 #endif
  45         return (oldcount < 0);
  46 }
  47
  48 static inline void __down_read(struct rw_semaphore *sem)
  49 {
  50         if (unlikely(___down_read(sem)))
  51                 rwsem_down_read_failed(sem);
  52 }
  53
  54 static inline int __down_read_killable(struct rw_semaphore *sem)
  55 {
  56         if (unlikely(___down_read(sem)))
  57                 if (IS_ERR(rwsem_down_read_failed_killable(sem)))
  58                         return -EINTR;
  59
  60         return 0;
  61 }
  62
  63 /*
  64  * trylock for reading -- returns 1 if successful, 0 if contention
  65  */
  66 static inline int __down_read_trylock(struct rw_semaphore *sem)
  67 {
  68         long old, new, res;
  69
  70         res = atomic_long_read(&sem->count);
  71         do {
  72                 new = res + RWSEM_ACTIVE_READ_BIAS;
  73                 if (new <= 0)
  74                         break;
  75                 old = res;
  76                 res = atomic_long_cmpxchg(&sem->count, old, new);
  77         } while (res != old);
  78         return res >= 0 ? 1 : 0;
  79 }
  80
  81 static inline long ___down_write(struct rw_semaphore *sem)
  82 {
  83         long oldcount;
  84 #ifndef CONFIG_SMP
  85         oldcount = sem->count.counter;
  86         sem->count.counter += RWSEM_ACTIVE_WRITE_BIAS;
  87 #else
  88         long temp;
  89         __asm__ __volatile__(
  90         "1:     ldq_l   %0,%1\n"
  91         "       addq    %0,%3,%2\n"
  92         "       stq_c   %2,%1\n"
  93         "       beq     %2,2f\n"
  94         "       mb\n"
  95         ".subsection 2\n"
  96         "2:     br      1b\n"
  97         ".previous"
  98         :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
  99         :"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");
 100 #endif
 101         return oldcount;
 102 }
 103
 104 static inline void __down_write(struct rw_semaphore *sem)
 105 {
 106         if (unlikely(___down_write(sem)))
 107                 rwsem_down_write_failed(sem);
 108 }
 109
 110 static inline int __down_write_killable(struct rw_semaphore *sem)
 111 {
 112         if (unlikely(___down_write(sem))) {
 113                 if (IS_ERR(rwsem_down_write_failed_killable(sem)))
 114                         return -EINTR;
 115         }
 116
 117         return 0;
 118 }
 119
 120 /*
 121  * trylock for writing -- returns 1 if successful, 0 if contention
 122  */
 123 static inline int __down_write_trylock(struct rw_semaphore *sem)
 124 {
 125         long ret = atomic_long_cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
 126                            RWSEM_ACTIVE_WRITE_BIAS);
 127         if (ret == RWSEM_UNLOCKED_VALUE)
 128                 return 1;
 129         return 0;
 130 }
 131
 132 static inline void __up_read(struct rw_semaphore *sem)
 133 {
 134         long oldcount;
 135 #ifndef CONFIG_SMP
 136         oldcount = sem->count.counter;
 137         sem->count.counter -= RWSEM_ACTIVE_READ_BIAS;
 138 #else
 139         long temp;
 140         __asm__ __volatile__(
 141         "       mb\n"
 142         "1:     ldq_l   %0,%1\n"
 143         "       subq    %0,%3,%2\n"
 144         "       stq_c   %2,%1\n"
 145         "       beq     %2,2f\n"
 146         ".subsection 2\n"
 147         "2:     br      1b\n"
 148         ".previous"
 149         :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
 150         :"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory");
 151 #endif
 152         if (unlikely(oldcount < 0))
 153                 if ((int)oldcount - RWSEM_ACTIVE_READ_BIAS == 0)
 154                         rwsem_wake(sem);
 155 }
 156
 157 static inline void __up_write(struct rw_semaphore *sem)
 158 {
 159         long count;
 160 #ifndef CONFIG_SMP
 161         sem->count.counter -= RWSEM_ACTIVE_WRITE_BIAS;
 162         count = sem->count.counter;
 163 #else
 164         long temp;
 165         __asm__ __volatile__(
 166         "       mb\n"
 167         "1:     ldq_l   %0,%1\n"
 168         "       subq    %0,%3,%2\n"
 169         "       stq_c   %2,%1\n"
 170         "       beq     %2,2f\n"
 171         "       subq    %0,%3,%0\n"
 172         ".subsection 2\n"
 173         "2:     br      1b\n"
 174         ".previous"
 175         :"=&r" (count), "=m" (sem->count), "=&r" (temp)
 176         :"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");
 177 #endif
 178         if (unlikely(count))
 179                 if ((int)count == 0)
 180                         rwsem_wake(sem);
 181 }
 182
 183 /*
 184  * downgrade write lock to read lock
 185  */
 186 static inline void __downgrade_write(struct rw_semaphore *sem)
 187 {
 188         long oldcount;
 189 #ifndef CONFIG_SMP
 190         oldcount = sem->count.counter;
 191         sem->count.counter -= RWSEM_WAITING_BIAS;
 192 #else
 193         long temp;
 194         __asm__ __volatile__(
 195         "1:     ldq_l   %0,%1\n"
 196         "       addq    %0,%3,%2\n"
 197         "       stq_c   %2,%1\n"
 198         "       beq     %2,2f\n"
 199         "       mb\n"
 200         ".subsection 2\n"
 201         "2:     br      1b\n"
 202         ".previous"
 203         :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
 204         :"Ir" (-RWSEM_WAITING_BIAS), "m" (sem->count) : "memory");
 205 #endif
 206         if (unlikely(oldcount < 0))
 207                 rwsem_downgrade_wake(sem);
 208 }
 209
 210 #endif /* __KERNEL__ */
 211 #endif /* _ALPHA_RWSEM_H */