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 void __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         if (unlikely(oldcount < 0))
  46                 rwsem_down_read_failed(sem);
  47 }
  48
  49 /*
  50  * trylock for reading -- returns 1 if successful, 0 if contention
  51  */
  52 static inline int __down_read_trylock(struct rw_semaphore *sem)
  53 {
  54         long old, new, res;
  55
  56         res = atomic_long_read(&sem->count);
  57         do {
  58                 new = res + RWSEM_ACTIVE_READ_BIAS;
  59                 if (new <= 0)
  60                         break;
  61                 old = res;
  62                 res = atomic_long_cmpxchg(&sem->count, old, new);
  63         } while (res != old);
  64         return res >= 0 ? 1 : 0;
  65 }
  66
  67 static inline long ___down_write(struct rw_semaphore *sem)
  68 {
  69         long oldcount;
  70 #ifndef CONFIG_SMP
  71         oldcount = sem->count.counter;
  72         sem->count.counter += RWSEM_ACTIVE_WRITE_BIAS;
  73 #else
  74         long temp;
  75         __asm__ __volatile__(
  76         "1:     ldq_l   %0,%1\n"
  77         "       addq    %0,%3,%2\n"
  78         "       stq_c   %2,%1\n"
  79         "       beq     %2,2f\n"
  80         "       mb\n"
  81         ".subsection 2\n"
  82         "2:     br      1b\n"
  83         ".previous"
  84         :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
  85         :"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");
  86 #endif
  87         return oldcount;
  88 }
  89
  90 static inline void __down_write(struct rw_semaphore *sem)
  91 {
  92         if (unlikely(___down_write(sem)))
  93                 rwsem_down_write_failed(sem);
  94 }
  95
  96 static inline int __down_write_killable(struct rw_semaphore *sem)
  97 {
  98         if (unlikely(___down_write(sem)))
  99                 if (IS_ERR(rwsem_down_write_failed_killable(sem)))
 100                         return -EINTR;
 101
 102         return 0;
 103 }
 104
 105 /*
 106  * trylock for writing -- returns 1 if successful, 0 if contention
 107  */
 108 static inline int __down_write_trylock(struct rw_semaphore *sem)
 109 {
 110         long ret = atomic_long_cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
 111                            RWSEM_ACTIVE_WRITE_BIAS);
 112         if (ret == RWSEM_UNLOCKED_VALUE)
 113                 return 1;
 114         return 0;
 115 }
 116
 117 static inline void __up_read(struct rw_semaphore *sem)
 118 {
 119         long oldcount;
 120 #ifndef CONFIG_SMP
 121         oldcount = sem->count.counter;
 122         sem->count.counter -= RWSEM_ACTIVE_READ_BIAS;
 123 #else
 124         long temp;
 125         __asm__ __volatile__(
 126         "       mb\n"
 127         "1:     ldq_l   %0,%1\n"
 128         "       subq    %0,%3,%2\n"
 129         "       stq_c   %2,%1\n"
 130         "       beq     %2,2f\n"
 131         ".subsection 2\n"
 132         "2:     br      1b\n"
 133         ".previous"
 134         :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
 135         :"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory");
 136 #endif
 137         if (unlikely(oldcount < 0))
 138                 if ((int)oldcount - RWSEM_ACTIVE_READ_BIAS == 0)
 139                         rwsem_wake(sem);
 140 }
 141
 142 static inline void __up_write(struct rw_semaphore *sem)
 143 {
 144         long count;
 145 #ifndef CONFIG_SMP
 146         sem->count.counter -= RWSEM_ACTIVE_WRITE_BIAS;
 147         count = sem->count.counter;
 148 #else
 149         long temp;
 150         __asm__ __volatile__(
 151         "       mb\n"
 152         "1:     ldq_l   %0,%1\n"
 153         "       subq    %0,%3,%2\n"
 154         "       stq_c   %2,%1\n"
 155         "       beq     %2,2f\n"
 156         "       subq    %0,%3,%0\n"
 157         ".subsection 2\n"
 158         "2:     br      1b\n"
 159         ".previous"
 160         :"=&r" (count), "=m" (sem->count), "=&r" (temp)
 161         :"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");
 162 #endif
 163         if (unlikely(count))
 164                 if ((int)count == 0)
 165                         rwsem_wake(sem);
 166 }
 167
 168 /*
 169  * downgrade write lock to read lock
 170  */
 171 static inline void __downgrade_write(struct rw_semaphore *sem)
 172 {
 173         long oldcount;
 174 #ifndef CONFIG_SMP
 175         oldcount = sem->count.counter;
 176         sem->count.counter -= RWSEM_WAITING_BIAS;
 177 #else
 178         long temp;
 179         __asm__ __volatile__(
 180         "1:     ldq_l   %0,%1\n"
 181         "       addq    %0,%3,%2\n"
 182         "       stq_c   %2,%1\n"
 183         "       beq     %2,2f\n"
 184         "       mb\n"
 185         ".subsection 2\n"
 186         "2:     br      1b\n"
 187         ".previous"
 188         :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
 189         :"Ir" (-RWSEM_WAITING_BIAS), "m" (sem->count) : "memory");
 190 #endif
 191         if (unlikely(oldcount < 0))
 192                 rwsem_downgrade_wake(sem);
 193 }
 194
 195 #endif /* __KERNEL__ */
 196 #endif /* _ALPHA_RWSEM_H */