arch/s390/include/asm/rwsem.h

   1 #ifndef _S390_RWSEM_H
   2 #define _S390_RWSEM_H
   3
   4 /*
   5  *  include/asm-s390/rwsem.h
   6  *
   7  *  S390 version
   8  *    Copyright (C) 2002 IBM Deutschland Entwicklung GmbH, IBM Corporation
   9  *    Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
  10  *
  11  *  Based on asm-alpha/semaphore.h and asm-i386/rwsem.h
  12  */
  13
  14 /*
  15  *
  16  * The MSW of the count is the negated number of active writers and waiting
  17  * lockers, and the LSW is the total number of active locks
  18  *
  19  * The lock count is initialized to 0 (no active and no waiting lockers).
  20  *
  21  * When a writer subtracts WRITE_BIAS, it'll get 0xffff0001 for the case of an
  22  * uncontended lock. This can be determined because XADD returns the old value.
  23  * Readers increment by 1 and see a positive value when uncontended, negative
  24  * if there are writers (and maybe) readers waiting (in which case it goes to
  25  * sleep).
  26  *
  27  * The value of WAITING_BIAS supports up to 32766 waiting processes. This can
  28  * be extended to 65534 by manually checking the whole MSW rather than relying
  29  * on the S flag.
  30  *
  31  * The value of ACTIVE_BIAS supports up to 65535 active processes.
  32  *
  33  * This should be totally fair - if anything is waiting, a process that wants a
  34  * lock will go to the back of the queue. When the currently active lock is
  35  * released, if there's a writer at the front of the queue, then that and only
  36  * that will be woken up; if there's a bunch of consequtive readers at the
  37  * front, then they'll all be woken up, but no other readers will be.
  38  */
  39
  40 #ifndef _LINUX_RWSEM_H
  41 #error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
  42 #endif
  43
  44 #ifdef __KERNEL__
  45
  46 #ifndef __s390x__
  47 #define RWSEM_UNLOCKED_VALUE    0x00000000
  48 #define RWSEM_ACTIVE_BIAS       0x00000001
  49 #define RWSEM_ACTIVE_MASK       0x0000ffff
  50 #define RWSEM_WAITING_BIAS      (-0x00010000)
  51 #else /* __s390x__ */
  52 #define RWSEM_UNLOCKED_VALUE    0x0000000000000000L
  53 #define RWSEM_ACTIVE_BIAS       0x0000000000000001L
  54 #define RWSEM_ACTIVE_MASK       0x00000000ffffffffL
  55 #define RWSEM_WAITING_BIAS      (-0x0000000100000000L)
  56 #endif /* __s390x__ */
  57 #define RWSEM_ACTIVE_READ_BIAS  RWSEM_ACTIVE_BIAS
  58 #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
  59
  60 /*
  61  * lock for reading
  62  */
  63 static inline void __down_read(struct rw_semaphore *sem)
  64 {
  65         signed long old, new;
  66
  67         asm volatile(
  68 #ifndef __s390x__
  69                 "       l       %0,%2\n"
  70                 "0:     lr      %1,%0\n"
  71                 "       ahi     %1,%4\n"
  72                 "       cs      %0,%1,%2\n"
  73                 "       jl      0b"
  74 #else /* __s390x__ */
  75                 "       lg      %0,%2\n"
  76                 "0:     lgr     %1,%0\n"
  77                 "       aghi    %1,%4\n"
  78                 "       csg     %0,%1,%2\n"
  79                 "       jl      0b"
  80 #endif /* __s390x__ */
  81                 : "=&d" (old), "=&d" (new), "=Q" (sem->count)
  82                 : "Q" (sem->count), "i" (RWSEM_ACTIVE_READ_BIAS)
  83                 : "cc", "memory");
  84         if (old < 0)
  85                 rwsem_down_read_failed(sem);
  86 }
  87
  88 /*
  89  * trylock for reading -- returns 1 if successful, 0 if contention
  90  */
  91 static inline int __down_read_trylock(struct rw_semaphore *sem)
  92 {
  93         signed long old, new;
  94
  95         asm volatile(
  96 #ifndef __s390x__
  97                 "       l       %0,%2\n"
  98                 "0:     ltr     %1,%0\n"
  99                 "       jm      1f\n"
 100                 "       ahi     %1,%4\n"
 101                 "       cs      %0,%1,%2\n"
 102                 "       jl      0b\n"
 103                 "1:"
 104 #else /* __s390x__ */
 105                 "       lg      %0,%2\n"
 106                 "0:     ltgr    %1,%0\n"
 107                 "       jm      1f\n"
 108                 "       aghi    %1,%4\n"
 109                 "       csg     %0,%1,%2\n"
 110                 "       jl      0b\n"
 111                 "1:"
 112 #endif /* __s390x__ */
 113                 : "=&d" (old), "=&d" (new), "=Q" (sem->count)
 114                 : "Q" (sem->count), "i" (RWSEM_ACTIVE_READ_BIAS)
 115                 : "cc", "memory");
 116         return old >= 0 ? 1 : 0;
 117 }
 118
 119 /*
 120  * lock for writing
 121  */
 122 static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
 123 {
 124         signed long old, new, tmp;
 125
 126         tmp = RWSEM_ACTIVE_WRITE_BIAS;
 127         asm volatile(
 128 #ifndef __s390x__
 129                 "       l       %0,%2\n"
 130                 "0:     lr      %1,%0\n"
 131                 "       a       %1,%4\n"
 132                 "       cs      %0,%1,%2\n"
 133                 "       jl      0b"
 134 #else /* __s390x__ */
 135                 "       lg      %0,%2\n"
 136                 "0:     lgr     %1,%0\n"
 137                 "       ag      %1,%4\n"
 138                 "       csg     %0,%1,%2\n"
 139                 "       jl      0b"
 140 #endif /* __s390x__ */
 141                 : "=&d" (old), "=&d" (new), "=Q" (sem->count)
 142                 : "Q" (sem->count), "m" (tmp)
 143                 : "cc", "memory");
 144         if (old != 0)
 145                 rwsem_down_write_failed(sem);
 146 }
 147
 148 static inline void __down_write(struct rw_semaphore *sem)
 149 {
 150         __down_write_nested(sem, 0);
 151 }
 152
 153 /*
 154  * trylock for writing -- returns 1 if successful, 0 if contention
 155  */
 156 static inline int __down_write_trylock(struct rw_semaphore *sem)
 157 {
 158         signed long old;
 159
 160         asm volatile(
 161 #ifndef __s390x__
 162                 "       l       %0,%1\n"
 163                 "0:     ltr     %0,%0\n"
 164                 "       jnz     1f\n"
 165                 "       cs      %0,%3,%1\n"
 166                 "       jl      0b\n"
 167 #else /* __s390x__ */
 168                 "       lg      %0,%1\n"
 169                 "0:     ltgr    %0,%0\n"
 170                 "       jnz     1f\n"
 171                 "       csg     %0,%3,%1\n"
 172                 "       jl      0b\n"
 173 #endif /* __s390x__ */
 174                 "1:"
 175                 : "=&d" (old), "=Q" (sem->count)
 176                 : "Q" (sem->count), "d" (RWSEM_ACTIVE_WRITE_BIAS)
 177                 : "cc", "memory");
 178         return (old == RWSEM_UNLOCKED_VALUE) ? 1 : 0;
 179 }
 180
 181 /*
 182  * unlock after reading
 183  */
 184 static inline void __up_read(struct rw_semaphore *sem)
 185 {
 186         signed long old, new;
 187
 188         asm volatile(
 189 #ifndef __s390x__
 190                 "       l       %0,%2\n"
 191                 "0:     lr      %1,%0\n"
 192                 "       ahi     %1,%4\n"
 193                 "       cs      %0,%1,%2\n"
 194                 "       jl      0b"
 195 #else /* __s390x__ */
 196                 "       lg      %0,%2\n"
 197                 "0:     lgr     %1,%0\n"
 198                 "       aghi    %1,%4\n"
 199                 "       csg     %0,%1,%2\n"
 200                 "       jl      0b"
 201 #endif /* __s390x__ */
 202                 : "=&d" (old), "=&d" (new), "=Q" (sem->count)
 203                 : "Q" (sem->count), "i" (-RWSEM_ACTIVE_READ_BIAS)
 204                 : "cc", "memory");
 205         if (new < 0)
 206                 if ((new & RWSEM_ACTIVE_MASK) == 0)
 207                         rwsem_wake(sem);
 208 }
 209
 210 /*
 211  * unlock after writing
 212  */
 213 static inline void __up_write(struct rw_semaphore *sem)
 214 {
 215         signed long old, new, tmp;
 216
 217         tmp = -RWSEM_ACTIVE_WRITE_BIAS;
 218         asm volatile(
 219 #ifndef __s390x__
 220                 "       l       %0,%2\n"
 221                 "0:     lr      %1,%0\n"
 222                 "       a       %1,%4\n"
 223                 "       cs      %0,%1,%2\n"
 224                 "       jl      0b"
 225 #else /* __s390x__ */
 226                 "       lg      %0,%2\n"
 227                 "0:     lgr     %1,%0\n"
 228                 "       ag      %1,%4\n"
 229                 "       csg     %0,%1,%2\n"
 230                 "       jl      0b"
 231 #endif /* __s390x__ */
 232                 : "=&d" (old), "=&d" (new), "=Q" (sem->count)
 233                 : "Q" (sem->count), "m" (tmp)
 234                 : "cc", "memory");
 235         if (new < 0)
 236                 if ((new & RWSEM_ACTIVE_MASK) == 0)
 237                         rwsem_wake(sem);
 238 }
 239
 240 /*
 241  * downgrade write lock to read lock
 242  */
 243 static inline void __downgrade_write(struct rw_semaphore *sem)
 244 {
 245         signed long old, new, tmp;
 246
 247         tmp = -RWSEM_WAITING_BIAS;
 248         asm volatile(
 249 #ifndef __s390x__
 250                 "       l       %0,%2\n"
 251                 "0:     lr      %1,%0\n"
 252                 "       a       %1,%4\n"
 253                 "       cs      %0,%1,%2\n"
 254                 "       jl      0b"
 255 #else /* __s390x__ */
 256                 "       lg      %0,%2\n"
 257                 "0:     lgr     %1,%0\n"
 258                 "       ag      %1,%4\n"
 259                 "       csg     %0,%1,%2\n"
 260                 "       jl      0b"
 261 #endif /* __s390x__ */
 262                 : "=&d" (old), "=&d" (new), "=Q" (sem->count)
 263                 : "Q" (sem->count), "m" (tmp)
 264                 : "cc", "memory");
 265         if (new > 1)
 266                 rwsem_downgrade_wake(sem);
 267 }
 268
 269 /*
 270  * implement atomic add functionality
 271  */
 272 static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
 273 {
 274         signed long old, new;
 275
 276         asm volatile(
 277 #ifndef __s390x__
 278                 "       l       %0,%2\n"
 279                 "0:     lr      %1,%0\n"
 280                 "       ar      %1,%4\n"
 281                 "       cs      %0,%1,%2\n"
 282                 "       jl      0b"
 283 #else /* __s390x__ */
 284                 "       lg      %0,%2\n"
 285                 "0:     lgr     %1,%0\n"
 286                 "       agr     %1,%4\n"
 287                 "       csg     %0,%1,%2\n"
 288                 "       jl      0b"
 289 #endif /* __s390x__ */
 290                 : "=&d" (old), "=&d" (new), "=Q" (sem->count)
 291                 : "Q" (sem->count), "d" (delta)
 292                 : "cc", "memory");
 293 }
 294
 295 /*
 296  * implement exchange and add functionality
 297  */
 298 static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
 299 {
 300         signed long old, new;
 301
 302         asm volatile(
 303 #ifndef __s390x__
 304                 "       l       %0,%2\n"
 305                 "0:     lr      %1,%0\n"
 306                 "       ar      %1,%4\n"
 307                 "       cs      %0,%1,%2\n"
 308                 "       jl      0b"
 309 #else /* __s390x__ */
 310                 "       lg      %0,%2\n"
 311                 "0:     lgr     %1,%0\n"
 312                 "       agr     %1,%4\n"
 313                 "       csg     %0,%1,%2\n"
 314                 "       jl      0b"
 315 #endif /* __s390x__ */
 316                 : "=&d" (old), "=&d" (new), "=Q" (sem->count)
 317                 : "Q" (sem->count), "d" (delta)
 318                 : "cc", "memory");
 319         return new;
 320 }
 321
 322 #endif /* __KERNEL__ */
 323 #endif /* _S390_RWSEM_H */