source4/lib/tdb/spinlock.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    trivial database library
   5
   6    Copyright (C) Anton Blanchard                   2001
   7
   8      ** NOTE! The following LGPL license applies to the tdb
   9      ** library. This does NOT imply that all of Samba is released
  10      ** under the LGPL
  11
  12    This library is free software; you can redistribute it and/or
  13    modify it under the terms of the GNU Lesser General Public
  14    License as published by the Free Software Foundation; either
  15    version 2 of the License, or (at your option) any later version.
  16
  17    This library is distributed in the hope that it will be useful,
  18    but WITHOUT ANY WARRANTY; without even the implied warranty of
  19    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  20    Lesser General Public License for more details.
  21
  22    You should have received a copy of the GNU Lesser General Public
  23    License along with this library; if not, write to the Free Software
  24    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  25 */
  26 #if HAVE_CONFIG_H
  27 #include <config.h>
  28 #endif
  29
  30 #if STANDALONE
  31 #include <stdlib.h>
  32 #include <stdio.h>
  33 #include <unistd.h>
  34 #include <string.h>
  35 #include <fcntl.h>
  36 #include <errno.h>
  37 #include <sys/stat.h>
  38 #include <time.h>
  39 #include <signal.h>
  40 #include "tdb.h"
  41 #include "spinlock.h"
  42
  43 #define DEBUG
  44 #else
  45 #include "includes.h"
  46 #endif
  47
  48 #ifdef USE_SPINLOCKS
  49
  50 /*
  51  * ARCH SPECIFIC
  52  */
  53
  54 #if defined(SPARC_SPINLOCKS)
  55
  56 static inline int __spin_trylock(spinlock_t *lock)
  57 {
  58         unsigned int result;
  59
  60         asm volatile("ldstub    [%1], %0"
  61                 : "=r" (result)
  62                 : "r" (lock)
  63                 : "memory");
  64
  65         return (result == 0) ? 0 : EBUSY;
  66 }
  67
  68 static inline void __spin_unlock(spinlock_t *lock)
  69 {
  70         asm volatile("":::"memory");
  71         *lock = 0;
  72 }
  73
  74 static inline void __spin_lock_init(spinlock_t *lock)
  75 {
  76         *lock = 0;
  77 }
  78
  79 static inline int __spin_is_locked(spinlock_t *lock)
  80 {
  81         return (*lock != 0);
  82 }
  83
  84 #elif defined(POWERPC_SPINLOCKS)
  85
  86 static inline int __spin_trylock(spinlock_t *lock)
  87 {
  88         unsigned int result;
  89
  90         __asm__ __volatile__(
  91 "1:     lwarx           %0,0,%1\n\
  92         cmpwi           0,%0,0\n\
  93         li              %0,0\n\
  94         bne-            2f\n\
  95         li              %0,1\n\
  96         stwcx.          %0,0,%1\n\
  97         bne-            1b\n\
  98         isync\n\
  99 2:"     : "=&r"(result)
 100         : "r"(lock)
 101         : "cr0", "memory");
 102
 103         return (result == 1) ? 0 : EBUSY;
 104 }
 105
 106 static inline void __spin_unlock(spinlock_t *lock)
 107 {
 108         asm volatile("eieio":::"memory");
 109         *lock = 0;
 110 }
 111
 112 static inline void __spin_lock_init(spinlock_t *lock)
 113 {
 114         *lock = 0;
 115 }
 116
 117 static inline int __spin_is_locked(spinlock_t *lock)
 118 {
 119         return (*lock != 0);
 120 }
 121
 122 #elif defined(INTEL_SPINLOCKS)
 123
 124 static inline int __spin_trylock(spinlock_t *lock)
 125 {
 126         int oldval;
 127
 128         asm volatile("xchgl %0,%1"
 129                 : "=r" (oldval), "=m" (*lock)
 130                 : "0" (0)
 131                 : "memory");
 132
 133         return oldval > 0 ? 0 : EBUSY;
 134 }
 135
 136 static inline void __spin_unlock(spinlock_t *lock)
 137 {
 138         asm volatile("":::"memory");
 139         *lock = 1;
 140 }
 141
 142 static inline void __spin_lock_init(spinlock_t *lock)
 143 {
 144         *lock = 1;
 145 }
 146
 147 static inline int __spin_is_locked(spinlock_t *lock)
 148 {
 149         return (*lock != 1);
 150 }
 151
 152 #elif defined(MIPS_SPINLOCKS)
 153
 154 static inline unsigned int load_linked(unsigned long addr)
 155 {
 156         unsigned int res;
 157
 158         __asm__ __volatile__("ll\t%0,(%1)"
 159                 : "=r" (res)
 160                 : "r" (addr));
 161
 162         return res;
 163 }
 164
 165 static inline unsigned int store_conditional(unsigned long addr, unsigned int value)
 166 {
 167         unsigned int res;
 168
 169         __asm__ __volatile__("sc\t%0,(%2)"
 170                 : "=r" (res)
 171                 : "0" (value), "r" (addr));
 172         return res;
 173 }
 174
 175 static inline int __spin_trylock(spinlock_t *lock)
 176 {
 177         unsigned int mw;
 178
 179         do {
 180                 mw = load_linked(lock);
 181                 if (mw)
 182                         return EBUSY;
 183         } while (!store_conditional(lock, 1));
 184
 185         asm volatile("":::"memory");
 186
 187         return 0;
 188 }
 189
 190 static inline void __spin_unlock(spinlock_t *lock)
 191 {
 192         asm volatile("":::"memory");
 193         *lock = 0;
 194 }
 195
 196 static inline void __spin_lock_init(spinlock_t *lock)
 197 {
 198         *lock = 0;
 199 }
 200
 201 static inline int __spin_is_locked(spinlock_t *lock)
 202 {
 203         return (*lock != 0);
 204 }
 205
 206 #else
 207 #error Need to implement spinlock code in spinlock.c
 208 #endif
 209
 210 /*
 211  * OS SPECIFIC
 212  */
 213
 214 static void yield_cpu(void)
 215 {
 216         struct timespec tm;
 217
 218 #ifdef USE_SCHED_YIELD
 219         sched_yield();
 220 #else
 221         /* Linux will busy loop for delays < 2ms on real time tasks */
 222         tm.tv_sec = 0;
 223         tm.tv_nsec = 2000000L + 1;
 224         nanosleep(&tm, NULL);
 225 #endif
 226 }
 227
 228 static int this_is_smp(void)
 229 {
 230         return 0;
 231 }
 232
 233 /*
 234  * GENERIC
 235  */
 236
 237 static int smp_machine = 0;
 238
 239 static inline void __spin_lock(spinlock_t *lock)
 240 {
 241         int ntries = 0;
 242
 243         while(__spin_trylock(lock)) {
 244                 while(__spin_is_locked(lock)) {
 245                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 246                                 continue;
 247                         yield_cpu();
 248                 }
 249         }
 250 }
 251
 252 static void __read_lock(tdb_rwlock_t *rwlock)
 253 {
 254         int ntries = 0;
 255
 256         while(1) {
 257                 __spin_lock(&rwlock->lock);
 258
 259                 if (!(rwlock->count & RWLOCK_BIAS)) {
 260                         rwlock->count++;
 261                         __spin_unlock(&rwlock->lock);
 262                         return;
 263                 }
 264
 265                 __spin_unlock(&rwlock->lock);
 266
 267                 while(rwlock->count & RWLOCK_BIAS) {
 268                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 269                                 continue;
 270                         yield_cpu();
 271                 }
 272         }
 273 }
 274
 275 static void __write_lock(tdb_rwlock_t *rwlock)
 276 {
 277         int ntries = 0;
 278
 279         while(1) {
 280                 __spin_lock(&rwlock->lock);
 281
 282                 if (rwlock->count == 0) {
 283                         rwlock->count |= RWLOCK_BIAS;
 284                         __spin_unlock(&rwlock->lock);
 285                         return;
 286                 }
 287
 288                 __spin_unlock(&rwlock->lock);
 289
 290                 while(rwlock->count != 0) {
 291                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 292                                 continue;
 293                         yield_cpu();
 294                 }
 295         }
 296 }
 297
 298 static void __write_unlock(tdb_rwlock_t *rwlock)
 299 {
 300         __spin_lock(&rwlock->lock);
 301
 302 #ifdef DEBUG
 303         if (!(rwlock->count & RWLOCK_BIAS))
 304                 fprintf(stderr, "bug: write_unlock\n");
 305 #endif
 306
 307         rwlock->count &= ~RWLOCK_BIAS;
 308         __spin_unlock(&rwlock->lock);
 309 }
 310
 311 static void __read_unlock(tdb_rwlock_t *rwlock)
 312 {
 313         __spin_lock(&rwlock->lock);
 314
 315 #ifdef DEBUG
 316         if (!rwlock->count)
 317                 fprintf(stderr, "bug: read_unlock\n");
 318
 319         if (rwlock->count & RWLOCK_BIAS)
 320                 fprintf(stderr, "bug: read_unlock\n");
 321 #endif
 322
 323         rwlock->count--;
 324         __spin_unlock(&rwlock->lock);
 325 }
 326
 327 /* TDB SPECIFIC */
 328
 329 /* lock a list in the database. list -1 is the alloc list */
 330 int tdb_spinlock(TDB_CONTEXT *tdb, int list, int rw_type)
 331 {
 332         tdb_rwlock_t *rwlocks;
 333
 334         if (!tdb->map_ptr) return -1;
 335         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 336
 337         switch(rw_type) {
 338         case F_RDLCK:
 339                 __read_lock(&rwlocks[list+1]);
 340                 break;
 341
 342         case F_WRLCK:
 343                 __write_lock(&rwlocks[list+1]);
 344                 break;
 345
 346         default:
 347                 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
 348         }
 349         return 0;
 350 }
 351
 352 /* unlock the database. */
 353 int tdb_spinunlock(TDB_CONTEXT *tdb, int list, int rw_type)
 354 {
 355         tdb_rwlock_t *rwlocks;
 356
 357         if (!tdb->map_ptr) return -1;
 358         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 359
 360         switch(rw_type) {
 361         case F_RDLCK:
 362                 __read_unlock(&rwlocks[list+1]);
 363                 break;
 364
 365         case F_WRLCK:
 366                 __write_unlock(&rwlocks[list+1]);
 367                 break;
 368
 369         default:
 370                 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
 371         }
 372
 373         return 0;
 374 }
 375
 376 int tdb_create_rwlocks(int fd, unsigned int hash_size)
 377 {
 378         unsigned size, i;
 379         tdb_rwlock_t *rwlocks;
 380
 381         size = TDB_SPINLOCK_SIZE(hash_size);
 382         rwlocks = malloc(size);
 383         if (!rwlocks)
 384                 return -1;
 385
 386         for(i = 0; i < hash_size+1; i++) {
 387                 __spin_lock_init(&rwlocks[i].lock);
 388                 rwlocks[i].count = 0;
 389         }
 390
 391         /* Write it out (appending to end) */
 392         if (write(fd, rwlocks, size) != size) {
 393                 free(rwlocks);
 394                 return -1;
 395         }
 396         smp_machine = this_is_smp();
 397         free(rwlocks);
 398         return 0;
 399 }
 400
 401 int tdb_clear_spinlocks(TDB_CONTEXT *tdb)
 402 {
 403         tdb_rwlock_t *rwlocks;
 404         unsigned i;
 405
 406         if (tdb->header.rwlocks == 0) return 0;
 407         if (!tdb->map_ptr) return -1;
 408
 409         /* We're mmapped here */
 410         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 411         for(i = 0; i < tdb->header.hash_size+1; i++) {
 412                 __spin_lock_init(&rwlocks[i].lock);
 413                 rwlocks[i].count = 0;
 414         }
 415         return 0;
 416 }
 417 #else
 418 int tdb_create_rwlocks(int fd, unsigned int hash_size) { return 0; }
 419 int tdb_spinlock(TDB_CONTEXT *tdb, int list, int rw_type) { return -1; }
 420 int tdb_spinunlock(TDB_CONTEXT *tdb, int list, int rw_type) { return -1; }
 421
 422 /* Non-spinlock version: remove spinlock pointer */
 423 int tdb_clear_spinlocks(TDB_CONTEXT *tdb)
 424 {
 425         tdb_off off = (tdb_off)((char *)&tdb->header.rwlocks
 426                                 - (char *)&tdb->header);
 427
 428         tdb->header.rwlocks = 0;
 429         if (lseek(tdb->fd, off, SEEK_SET) != off
 430             || write(tdb->fd, (void *)&tdb->header.rwlocks,
 431                      sizeof(tdb->header.rwlocks))
 432             != sizeof(tdb->header.rwlocks))
 433                 return -1;
 434         return 0;
 435 }
 436 #endif