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#include <linux/list.h> 47#include <linux/spinlock.h> 48 49struct rwsem_waiter; 50 51extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *); 52extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *); 53extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *); 54extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *); 55extern struct rw_semaphore *rwsem_downgrade_write(struct rw_semaphore *); 56 57/* 58 * the semaphore definition 59 */ 60struct rw_semaphore { 61 signed long count; 62 spinlock_t wait_lock; 63 struct list_head wait_list; 64#ifdef CONFIG_DEBUG_LOCK_ALLOC 65 struct lockdep_map dep_map; 66#endif 67}; 68 69#ifndef __s390x__ 70#define RWSEM_UNLOCKED_VALUE 0x00000000 71#define RWSEM_ACTIVE_BIAS 0x00000001 72#define RWSEM_ACTIVE_MASK 0x0000ffff 73#define RWSEM_WAITING_BIAS (-0x00010000) 74#else /* __s390x__ */ 75#define RWSEM_UNLOCKED_VALUE 0x0000000000000000L 76#define RWSEM_ACTIVE_BIAS 0x0000000000000001L 77#define RWSEM_ACTIVE_MASK 0x00000000ffffffffL 78#define RWSEM_WAITING_BIAS (-0x0000000100000000L) 79#endif /* __s390x__ */ 80#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS 81#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS) 82 83/* 84 * initialisation 85 */ 86 87#ifdef CONFIG_DEBUG_LOCK_ALLOC 88# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname } 89#else 90# define __RWSEM_DEP_MAP_INIT(lockname) 91#endif 92 93#define __RWSEM_INITIALIZER(name) \ 94 { RWSEM_UNLOCKED_VALUE, __SPIN_LOCK_UNLOCKED((name).wait.lock), \ 95 LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) } 96 97#define DECLARE_RWSEM(name) \ 98 struct rw_semaphore name = __RWSEM_INITIALIZER(name) 99 100static inline void init_rwsem(struct rw_semaphore *sem) 101{ 102 sem->count = RWSEM_UNLOCKED_VALUE; 103 spin_lock_init(&sem->wait_lock); 104 INIT_LIST_HEAD(&sem->wait_list); 105} 106 107extern void __init_rwsem(struct rw_semaphore *sem, const char *name, 108 struct lock_class_key *key); 109 110#define init_rwsem(sem) \ 111do { \ 112 static struct lock_class_key __key; \ 113 \ 114 __init_rwsem((sem), #sem, &__key); \ 115} while (0) 116 117 118/* 119 * lock for reading 120 */ 121static inline void __down_read(struct rw_semaphore *sem) 122{ 123 signed long old, new; 124 125 asm volatile( 126#ifndef __s390x__ 127 " l %0,%2\n" 128 "0: lr %1,%0\n" 129 " ahi %1,%4\n" 130 " cs %0,%1,%2\n" 131 " jl 0b" 132#else /* __s390x__ */ 133 " lg %0,%2\n" 134 "0: lgr %1,%0\n" 135 " aghi %1,%4\n" 136 " csg %0,%1,%2\n" 137 " jl 0b" 138#endif /* __s390x__ */ 139 : "=&d" (old), "=&d" (new), "=Q" (sem->count) 140 : "Q" (sem->count), "i" (RWSEM_ACTIVE_READ_BIAS) 141 : "cc", "memory"); 142 if (old < 0) 143 rwsem_down_read_failed(sem); 144} 145 146/* 147 * trylock for reading -- returns 1 if successful, 0 if contention 148 */ 149static inline int __down_read_trylock(struct rw_semaphore *sem) 150{ 151 signed long old, new; 152 153 asm volatile( 154#ifndef __s390x__ 155 " l %0,%2\n" 156 "0: ltr %1,%0\n" 157 " jm 1f\n" 158 " ahi %1,%4\n" 159 " cs %0,%1,%2\n" 160 " jl 0b\n" 161 "1:" 162#else /* __s390x__ */ 163 " lg %0,%2\n" 164 "0: ltgr %1,%0\n" 165 " jm 1f\n" 166 " aghi %1,%4\n" 167 " csg %0,%1,%2\n" 168 " jl 0b\n" 169 "1:" 170#endif /* __s390x__ */ 171 : "=&d" (old), "=&d" (new), "=Q" (sem->count) 172 : "Q" (sem->count), "i" (RWSEM_ACTIVE_READ_BIAS) 173 : "cc", "memory"); 174 return old >= 0 ? 1 : 0; 175} 176 177/* 178 * lock for writing 179 */ 180static inline void __down_write_nested(struct rw_semaphore *sem, int subclass) 181{ 182 signed long old, new, tmp; 183 184 tmp = RWSEM_ACTIVE_WRITE_BIAS; 185 asm volatile( 186#ifndef __s390x__ 187 " l %0,%2\n" 188 "0: lr %1,%0\n" 189 " a %1,%4\n" 190 " cs %0,%1,%2\n" 191 " jl 0b" 192#else /* __s390x__ */ 193 " lg %0,%2\n" 194 "0: lgr %1,%0\n" 195 " ag %1,%4\n" 196 " csg %0,%1,%2\n" 197 " jl 0b" 198#endif /* __s390x__ */ 199 : "=&d" (old), "=&d" (new), "=Q" (sem->count) 200 : "Q" (sem->count), "m" (tmp) 201 : "cc", "memory"); 202 if (old != 0) 203 rwsem_down_write_failed(sem); 204} 205 206static inline void __down_write(struct rw_semaphore *sem) 207{ 208 __down_write_nested(sem, 0); 209} 210 211/* 212 * trylock for writing -- returns 1 if successful, 0 if contention 213 */ 214static inline int __down_write_trylock(struct rw_semaphore *sem) 215{ 216 signed long old; 217 218 asm volatile( 219#ifndef __s390x__ 220 " l %0,%1\n" 221 "0: ltr %0,%0\n" 222 " jnz 1f\n" 223 " cs %0,%3,%1\n" 224 " jl 0b\n" 225#else /* __s390x__ */ 226 " lg %0,%1\n" 227 "0: ltgr %0,%0\n" 228 " jnz 1f\n" 229 " csg %0,%3,%1\n" 230 " jl 0b\n" 231#endif /* __s390x__ */ 232 "1:" 233 : "=&d" (old), "=Q" (sem->count) 234 : "Q" (sem->count), "d" (RWSEM_ACTIVE_WRITE_BIAS) 235 : "cc", "memory"); 236 return (old == RWSEM_UNLOCKED_VALUE) ? 1 : 0; 237} 238 239/* 240 * unlock after reading 241 */ 242static inline void __up_read(struct rw_semaphore *sem) 243{ 244 signed long old, new; 245 246 asm volatile( 247#ifndef __s390x__ 248 " l %0,%2\n" 249 "0: lr %1,%0\n" 250 " ahi %1,%4\n" 251 " cs %0,%1,%2\n" 252 " jl 0b" 253#else /* __s390x__ */ 254 " lg %0,%2\n" 255 "0: lgr %1,%0\n" 256 " aghi %1,%4\n" 257 " csg %0,%1,%2\n" 258 " jl 0b" 259#endif /* __s390x__ */ 260 : "=&d" (old), "=&d" (new), "=Q" (sem->count) 261 : "Q" (sem->count), "i" (-RWSEM_ACTIVE_READ_BIAS) 262 : "cc", "memory"); 263 if (new < 0) 264 if ((new & RWSEM_ACTIVE_MASK) == 0) 265 rwsem_wake(sem); 266} 267 268/* 269 * unlock after writing 270 */ 271static inline void __up_write(struct rw_semaphore *sem) 272{ 273 signed long old, new, tmp; 274 275 tmp = -RWSEM_ACTIVE_WRITE_BIAS; 276 asm volatile( 277#ifndef __s390x__ 278 " l %0,%2\n" 279 "0: lr %1,%0\n" 280 " a %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 " ag %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), "m" (tmp) 292 : "cc", "memory"); 293 if (new < 0) 294 if ((new & RWSEM_ACTIVE_MASK) == 0) 295 rwsem_wake(sem); 296} 297 298/* 299 * downgrade write lock to read lock 300 */ 301static inline void __downgrade_write(struct rw_semaphore *sem) 302{ 303 signed long old, new, tmp; 304 305 tmp = -RWSEM_WAITING_BIAS; 306 asm volatile( 307#ifndef __s390x__ 308 " l %0,%2\n" 309 "0: lr %1,%0\n" 310 " a %1,%4\n" 311 " cs %0,%1,%2\n" 312 " jl 0b" 313#else /* __s390x__ */ 314 " lg %0,%2\n" 315 "0: lgr %1,%0\n" 316 " ag %1,%4\n" 317 " csg %0,%1,%2\n" 318 " jl 0b" 319#endif /* __s390x__ */ 320 : "=&d" (old), "=&d" (new), "=Q" (sem->count) 321 : "Q" (sem->count), "m" (tmp) 322 : "cc", "memory"); 323 if (new > 1) 324 rwsem_downgrade_wake(sem); 325} 326 327/* 328 * implement atomic add functionality 329 */ 330static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem) 331{ 332 signed long old, new; 333 334 asm volatile( 335#ifndef __s390x__ 336 " l %0,%2\n" 337 "0: lr %1,%0\n" 338 " ar %1,%4\n" 339 " cs %0,%1,%2\n" 340 " jl 0b" 341#else /* __s390x__ */ 342 " lg %0,%2\n" 343 "0: lgr %1,%0\n" 344 " agr %1,%4\n" 345 " csg %0,%1,%2\n" 346 " jl 0b" 347#endif /* __s390x__ */ 348 : "=&d" (old), "=&d" (new), "=Q" (sem->count) 349 : "Q" (sem->count), "d" (delta) 350 : "cc", "memory"); 351} 352 353/* 354 * implement exchange and add functionality 355 */ 356static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem) 357{ 358 signed long old, new; 359 360 asm volatile( 361#ifndef __s390x__ 362 " l %0,%2\n" 363 "0: lr %1,%0\n" 364 " ar %1,%4\n" 365 " cs %0,%1,%2\n" 366 " jl 0b" 367#else /* __s390x__ */ 368 " lg %0,%2\n" 369 "0: lgr %1,%0\n" 370 " agr %1,%4\n" 371 " csg %0,%1,%2\n" 372 " jl 0b" 373#endif /* __s390x__ */ 374 : "=&d" (old), "=&d" (new), "=Q" (sem->count) 375 : "Q" (sem->count), "d" (delta) 376 : "cc", "memory"); 377 return new; 378} 379 380static inline int rwsem_is_locked(struct rw_semaphore *sem) 381{ 382 return (sem->count != 0); 383} 384 385#endif /* __KERNEL__ */ 386#endif /* _S390_RWSEM_H */ 387