tdb/spinlock.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    Samba database functions
   4    Copyright (C) Anton Blanchard                   2001
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software
  18    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19 */
  20 #if HAVE_CONFIG_H
  21 #include <config.h>
  22 #endif
  23
  24 #if STANDALONE
  25 #include <stdlib.h>
  26 #include <stdio.h>
  27 #include <unistd.h>
  28 #include <string.h>
  29 #include <fcntl.h>
  30 #include <errno.h>
  31 #include <sys/stat.h>
  32 #include <time.h>
  33 #include <signal.h>
  34 #include "tdb.h"
  35 #include "spinlock.h"
  36
  37 #define DEBUG
  38 #else
  39 #include "includes.h"
  40 #endif
  41
  42 #ifdef USE_SPINLOCKS
  43
  44 /*
  45  * ARCH SPECIFIC
  46  */
  47
  48 #if defined(SPARC_SPINLOCKS)
  49
  50 static inline int __spin_trylock(spinlock_t *lock)
  51 {
  52         unsigned int result;
  53
  54         asm volatile("ldstub    [%1], %0"
  55                 : "=r" (result)
  56                 : "r" (lock)
  57                 : "memory");
  58
  59         return (result == 0) ? 0 : EBUSY;
  60 }
  61
  62 static inline void __spin_unlock(spinlock_t *lock)
  63 {
  64         asm volatile("":::"memory");
  65         *lock = 0;
  66 }
  67
  68 static inline void __spin_lock_init(spinlock_t *lock)
  69 {
  70         *lock = 0;
  71 }
  72
  73 static inline int __spin_is_locked(spinlock_t *lock)
  74 {
  75         return (*lock != 0);
  76 }
  77
  78 #elif defined(POWERPC_SPINLOCKS)
  79
  80 static inline int __spin_trylock(spinlock_t *lock)
  81 {
  82         unsigned int result;
  83
  84         __asm__ __volatile__(
  85 "1:     lwarx           %0,0,%1\n\
  86         cmpwi           0,%0,0\n\
  87         li              %0,0\n\
  88         bne-            2f\n\
  89         li              %0,1\n\
  90         stwcx.          %0,0,%1\n\
  91         bne-            1b\n\
  92         isync\n\
  93 2:"     : "=&r"(result)
  94         : "r"(lock)
  95         : "cr0", "memory");
  96
  97         return (result == 1) ? 0 : EBUSY;
  98 }
  99
 100 static inline void __spin_unlock(spinlock_t *lock)
 101 {
 102         asm volatile("eieio":::"memory");
 103         *lock = 0;
 104 }
 105
 106 static inline void __spin_lock_init(spinlock_t *lock)
 107 {
 108         *lock = 0;
 109 }
 110
 111 static inline int __spin_is_locked(spinlock_t *lock)
 112 {
 113         return (*lock != 0);
 114 }
 115
 116 #elif defined(INTEL_SPINLOCKS)
 117
 118 static inline int __spin_trylock(spinlock_t *lock)
 119 {
 120         int oldval;
 121
 122         asm volatile("xchgl %0,%1"
 123                 : "=r" (oldval), "=m" (*lock)
 124                 : "0" (0)
 125                 : "memory");
 126
 127         return oldval > 0 ? 0 : EBUSY;
 128 }
 129
 130 static inline void __spin_unlock(spinlock_t *lock)
 131 {
 132         asm volatile("":::"memory");
 133         *lock = 1;
 134 }
 135
 136 static inline void __spin_lock_init(spinlock_t *lock)
 137 {
 138         *lock = 1;
 139 }
 140
 141 static inline int __spin_is_locked(spinlock_t *lock)
 142 {
 143         return (*lock != 1);
 144 }
 145
 146 #elif defined(MIPS_SPINLOCKS)
 147
 148 static inline unsigned int load_linked(unsigned long addr)
 149 {
 150         unsigned int res;
 151
 152         __asm__ __volatile__("ll\t%0,(%1)"
 153                 : "=r" (res)
 154                 : "r" (addr));
 155
 156         return res;
 157 }
 158
 159 static inline unsigned int store_conditional(unsigned long addr, unsigned int value)
 160 {
 161         unsigned int res;
 162
 163         __asm__ __volatile__("sc\t%0,(%2)"
 164                 : "=r" (res)
 165                 : "0" (value), "r" (addr));
 166         return res;
 167 }
 168
 169 static inline int __spin_trylock(spinlock_t *lock)
 170 {
 171         unsigned int mw;
 172
 173         do {
 174                 mw = load_linked(lock);
 175                 if (mw)
 176                         return EBUSY;
 177         } while (!store_conditional(lock, 1));
 178
 179         asm volatile("":::"memory");
 180
 181         return 0;
 182 }
 183
 184 static inline void __spin_unlock(spinlock_t *lock)
 185 {
 186         asm volatile("":::"memory");
 187         *lock = 0;
 188 }
 189
 190 static inline void __spin_lock_init(spinlock_t *lock)
 191 {
 192         *lock = 0;
 193 }
 194
 195 static inline int __spin_is_locked(spinlock_t *lock)
 196 {
 197         return (*lock != 0);
 198 }
 199
 200 #else
 201 #error Need to implement spinlock code in spinlock.c
 202 #endif
 203
 204 /*
 205  * OS SPECIFIC
 206  */
 207
 208 static void yield_cpu(void)
 209 {
 210         struct timespec tm;
 211
 212 #ifdef USE_SCHED_YIELD
 213         sched_yield();
 214 #else
 215         /* Linux will busy loop for delays < 2ms on real time tasks */
 216         tm.tv_sec = 0;
 217         tm.tv_nsec = 2000000L + 1;
 218         nanosleep(&tm, NULL);
 219 #endif
 220 }
 221
 222 static int this_is_smp(void)
 223 {
 224         return 0;
 225 }
 226
 227 /*
 228  * GENERIC
 229  */
 230
 231 static int smp_machine = 0;
 232
 233 static inline void __spin_lock(spinlock_t *lock)
 234 {
 235         int ntries = 0;
 236
 237         while(__spin_trylock(lock)) {
 238                 while(__spin_is_locked(lock)) {
 239                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 240                                 continue;
 241                         yield_cpu();
 242                 }
 243         }
 244 }
 245
 246 static void __read_lock(tdb_rwlock_t *rwlock)
 247 {
 248         int ntries = 0;
 249
 250         while(1) {
 251                 __spin_lock(&rwlock->lock);
 252
 253                 if (!(rwlock->count & RWLOCK_BIAS)) {
 254                         rwlock->count++;
 255                         __spin_unlock(&rwlock->lock);
 256                         return;
 257                 }
 258
 259                 __spin_unlock(&rwlock->lock);
 260
 261                 while(rwlock->count & RWLOCK_BIAS) {
 262                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 263                                 continue;
 264                         yield_cpu();
 265                 }
 266         }
 267 }
 268
 269 static void __write_lock(tdb_rwlock_t *rwlock)
 270 {
 271         int ntries = 0;
 272
 273         while(1) {
 274                 __spin_lock(&rwlock->lock);
 275
 276                 if (rwlock->count == 0) {
 277                         rwlock->count |= RWLOCK_BIAS;
 278                         __spin_unlock(&rwlock->lock);
 279                         return;
 280                 }
 281
 282                 __spin_unlock(&rwlock->lock);
 283
 284                 while(rwlock->count != 0) {
 285                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 286                                 continue;
 287                         yield_cpu();
 288                 }
 289         }
 290 }
 291
 292 static void __write_unlock(tdb_rwlock_t *rwlock)
 293 {
 294         __spin_lock(&rwlock->lock);
 295
 296 #ifdef DEBUG
 297         if (!(rwlock->count & RWLOCK_BIAS))
 298                 fprintf(stderr, "bug: write_unlock\n");
 299 #endif
 300
 301         rwlock->count &= ~RWLOCK_BIAS;
 302         __spin_unlock(&rwlock->lock);
 303 }
 304
 305 static void __read_unlock(tdb_rwlock_t *rwlock)
 306 {
 307         __spin_lock(&rwlock->lock);
 308
 309 #ifdef DEBUG
 310         if (!rwlock->count)
 311                 fprintf(stderr, "bug: read_unlock\n");
 312
 313         if (rwlock->count & RWLOCK_BIAS)
 314                 fprintf(stderr, "bug: read_unlock\n");
 315 #endif
 316
 317         rwlock->count--;
 318         __spin_unlock(&rwlock->lock);
 319 }
 320
 321 /* TDB SPECIFIC */
 322
 323 /* lock a list in the database. list -1 is the alloc list */
 324 int tdb_spinlock(TDB_CONTEXT *tdb, int list, int rw_type)
 325 {
 326         tdb_rwlock_t *rwlocks;
 327
 328         if (!tdb->map_ptr) return -1;
 329         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 330
 331         switch(rw_type) {
 332         case F_RDLCK:
 333                 __read_lock(&rwlocks[list+1]);
 334                 break;
 335
 336         case F_WRLCK:
 337                 __write_lock(&rwlocks[list+1]);
 338                 break;
 339
 340         default:
 341                 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
 342         }
 343         return 0;
 344 }
 345
 346 /* unlock the database. */
 347 int tdb_spinunlock(TDB_CONTEXT *tdb, int list, int rw_type)
 348 {
 349         tdb_rwlock_t *rwlocks;
 350
 351         if (!tdb->map_ptr) return -1;
 352         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 353
 354         switch(rw_type) {
 355         case F_RDLCK:
 356                 __read_unlock(&rwlocks[list+1]);
 357                 break;
 358
 359         case F_WRLCK:
 360                 __write_unlock(&rwlocks[list+1]);
 361                 break;
 362
 363         default:
 364                 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
 365         }
 366
 367         return 0;
 368 }
 369
 370 int tdb_create_rwlocks(int fd, unsigned int hash_size)
 371 {
 372         unsigned size, i;
 373         tdb_rwlock_t *rwlocks;
 374
 375         size = (hash_size + 1) * sizeof(tdb_rwlock_t);
 376         rwlocks = malloc(size);
 377         if (!rwlocks)
 378                 return -1;
 379
 380         for(i = 0; i < hash_size+1; i++) {
 381                 __spin_lock_init(&rwlocks[i].lock);
 382                 rwlocks[i].count = 0;
 383         }
 384
 385         /* Write it out (appending to end) */
 386         if (write(fd, rwlocks, size) != size) {
 387                 free(rwlocks);
 388                 return -1;
 389         }
 390         smp_machine = this_is_smp();
 391         free(rwlocks);
 392         return 0;
 393 }
 394
 395 int tdb_clear_spinlocks(TDB_CONTEXT *tdb)
 396 {
 397         tdb_rwlock_t *rwlocks;
 398         unsigned i;
 399
 400         if (tdb->header.rwlocks == 0) return 0;
 401         if (!tdb->map_ptr) return -1;
 402
 403         /* We're mmapped here */
 404         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 405         for(i = 0; i < tdb->header.hash_size+1; i++) {
 406                 __spin_lock_init(&rwlocks[i].lock);
 407                 rwlocks[i].count = 0;
 408         }
 409         return 0;
 410 }
 411 #else
 412 int tdb_create_rwlocks(int fd, unsigned int hash_size) { return 0; }
 413 int tdb_spinlock(TDB_CONTEXT *tdb, int list, int rw_type) { return -1; }
 414 int tdb_spinunlock(TDB_CONTEXT *tdb, int list, int rw_type) { return -1; }
 415
 416 /* Non-spinlock version: remove spinlock pointer */
 417 int tdb_clear_spinlocks(TDB_CONTEXT *tdb)
 418 {
 419         tdb_off off = (tdb_off)((char *)&tdb->header.rwlocks
 420                                 - (char *)&tdb->header);
 421
 422         tdb->header.rwlocks = 0;
 423         if (lseek(tdb->fd, off, SEEK_SET) != off
 424             || write(tdb->fd, (void *)&tdb->header.rwlocks,
 425                      sizeof(tdb->header.rwlocks))
 426             != sizeof(tdb->header.rwlocks))
 427                 return -1;
 428         return 0;
 429 }
 430 #endif