source/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) && defined(sgi) && (_COMPILER_VERSION >= 730)
 153
 154 /* Implement spinlocks on IRIX using the MIPSPro atomic fetch operations. See
 155  * sync(3) for the details of the intrinsic operations.
 156  *
 157  * "sgi" and "_COMPILER_VERSION" are always defined by MIPSPro.
 158  */
 159
 160 #if defined(STANDALONE)
 161
 162 /* MIPSPro 7.3 has "__inline" as an extension, but not "inline. */
 163 #define inline __inline
 164
 165 #endif /* STANDALONE */
 166
 167 /* Returns 0 if the lock is acquired, EBUSY otherwise. */
 168 static inline int __spin_trylock(spinlock_t *lock)
 169 {
 170         unsigned int val;
 171         val = __lock_test_and_set(lock, 1);
 172         return val == 0 ? 0 : EBUSY;
 173 }
 174
 175 static inline void __spin_unlock(spinlock_t *lock)
 176 {
 177         __lock_release(lock);
 178 }
 179
 180 static inline void __spin_lock_init(spinlock_t *lock)
 181 {
 182         __lock_release(lock);
 183 }
 184
 185 /* Returns 1 if the lock is held, 0 otherwise. */
 186 static inline int __spin_is_locked(spinlock_t *lock)
 187 {
 188         unsigned int val;
 189         val = __add_and_fetch(lock, 0);
 190         return val;
 191 }
 192
 193 #elif defined(MIPS_SPINLOCKS)
 194
 195 static inline unsigned int load_linked(unsigned long addr)
 196 {
 197         unsigned int res;
 198
 199         __asm__ __volatile__("ll\t%0,(%1)"
 200                 : "=r" (res)
 201                 : "r" (addr));
 202
 203         return res;
 204 }
 205
 206 static inline unsigned int store_conditional(unsigned long addr, unsigned int value)
 207 {
 208         unsigned int res;
 209
 210         __asm__ __volatile__("sc\t%0,(%2)"
 211                 : "=r" (res)
 212                 : "0" (value), "r" (addr));
 213         return res;
 214 }
 215
 216 static inline int __spin_trylock(spinlock_t *lock)
 217 {
 218         unsigned int mw;
 219
 220         do {
 221                 mw = load_linked(lock);
 222                 if (mw)
 223                         return EBUSY;
 224         } while (!store_conditional(lock, 1));
 225
 226         asm volatile("":::"memory");
 227
 228         return 0;
 229 }
 230
 231 static inline void __spin_unlock(spinlock_t *lock)
 232 {
 233         asm volatile("":::"memory");
 234         *lock = 0;
 235 }
 236
 237 static inline void __spin_lock_init(spinlock_t *lock)
 238 {
 239         *lock = 0;
 240 }
 241
 242 static inline int __spin_is_locked(spinlock_t *lock)
 243 {
 244         return (*lock != 0);
 245 }
 246
 247 #else
 248 #error Need to implement spinlock code in spinlock.c
 249 #endif
 250
 251 /*
 252  * OS SPECIFIC
 253  */
 254
 255 static void yield_cpu(void)
 256 {
 257         struct timespec tm;
 258
 259 #ifdef USE_SCHED_YIELD
 260         sched_yield();
 261 #else
 262         /* Linux will busy loop for delays < 2ms on real time tasks */
 263         tm.tv_sec = 0;
 264         tm.tv_nsec = 2000000L + 1;
 265         nanosleep(&tm, NULL);
 266 #endif
 267 }
 268
 269 static int this_is_smp(void)
 270 {
 271 #if defined(HAVE_SYSCONF) && defined(SYSCONF_SC_NPROC_ONLN)
 272         return (sysconf(_SC_NPROC_ONLN) > 1) ? 1 : 0;
 273 #else
 274         return 0;
 275 #endif
 276 }
 277
 278 /*
 279  * GENERIC
 280  */
 281
 282 static int smp_machine = 0;
 283
 284 static inline void __spin_lock(spinlock_t *lock)
 285 {
 286         int ntries = 0;
 287
 288         while(__spin_trylock(lock)) {
 289                 while(__spin_is_locked(lock)) {
 290                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 291                                 continue;
 292                         yield_cpu();
 293                 }
 294         }
 295 }
 296
 297 static void __read_lock(tdb_rwlock_t *rwlock)
 298 {
 299         int ntries = 0;
 300
 301         while(1) {
 302                 __spin_lock(&rwlock->lock);
 303
 304                 if (!(rwlock->count & RWLOCK_BIAS)) {
 305                         rwlock->count++;
 306                         __spin_unlock(&rwlock->lock);
 307                         return;
 308                 }
 309
 310                 __spin_unlock(&rwlock->lock);
 311
 312                 while(rwlock->count & RWLOCK_BIAS) {
 313                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 314                                 continue;
 315                         yield_cpu();
 316                 }
 317         }
 318 }
 319
 320 static void __write_lock(tdb_rwlock_t *rwlock)
 321 {
 322         int ntries = 0;
 323
 324         while(1) {
 325                 __spin_lock(&rwlock->lock);
 326
 327                 if (rwlock->count == 0) {
 328                         rwlock->count |= RWLOCK_BIAS;
 329                         __spin_unlock(&rwlock->lock);
 330                         return;
 331                 }
 332
 333                 __spin_unlock(&rwlock->lock);
 334
 335                 while(rwlock->count != 0) {
 336                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 337                                 continue;
 338                         yield_cpu();
 339                 }
 340         }
 341 }
 342
 343 static void __write_unlock(tdb_rwlock_t *rwlock)
 344 {
 345         __spin_lock(&rwlock->lock);
 346
 347 #ifdef DEBUG
 348         if (!(rwlock->count & RWLOCK_BIAS))
 349                 fprintf(stderr, "bug: write_unlock\n");
 350 #endif
 351
 352         rwlock->count &= ~RWLOCK_BIAS;
 353         __spin_unlock(&rwlock->lock);
 354 }
 355
 356 static void __read_unlock(tdb_rwlock_t *rwlock)
 357 {
 358         __spin_lock(&rwlock->lock);
 359
 360 #ifdef DEBUG
 361         if (!rwlock->count)
 362                 fprintf(stderr, "bug: read_unlock\n");
 363
 364         if (rwlock->count & RWLOCK_BIAS)
 365                 fprintf(stderr, "bug: read_unlock\n");
 366 #endif
 367
 368         rwlock->count--;
 369         __spin_unlock(&rwlock->lock);
 370 }
 371
 372 /* TDB SPECIFIC */
 373
 374 /* lock a list in the database. list -1 is the alloc list */
 375 int tdb_spinlock(TDB_CONTEXT *tdb, int list, int rw_type)
 376 {
 377         tdb_rwlock_t *rwlocks;
 378
 379         if (!tdb->map_ptr) return -1;
 380         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 381
 382         switch(rw_type) {
 383         case F_RDLCK:
 384                 __read_lock(&rwlocks[list+1]);
 385                 break;
 386
 387         case F_WRLCK:
 388                 __write_lock(&rwlocks[list+1]);
 389                 break;
 390
 391         default:
 392                 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
 393         }
 394         return 0;
 395 }
 396
 397 /* unlock the database. */
 398 int tdb_spinunlock(TDB_CONTEXT *tdb, int list, int rw_type)
 399 {
 400         tdb_rwlock_t *rwlocks;
 401
 402         if (!tdb->map_ptr) return -1;
 403         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 404
 405         switch(rw_type) {
 406         case F_RDLCK:
 407                 __read_unlock(&rwlocks[list+1]);
 408                 break;
 409
 410         case F_WRLCK:
 411                 __write_unlock(&rwlocks[list+1]);
 412                 break;
 413
 414         default:
 415                 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
 416         }
 417
 418         return 0;
 419 }
 420
 421 int tdb_create_rwlocks(int fd, unsigned int hash_size)
 422 {
 423         unsigned size, i;
 424         tdb_rwlock_t *rwlocks;
 425
 426         size = TDB_SPINLOCK_SIZE(hash_size);
 427         rwlocks = malloc(size);
 428         if (!rwlocks)
 429                 return -1;
 430
 431         for(i = 0; i < hash_size+1; i++) {
 432                 __spin_lock_init(&rwlocks[i].lock);
 433                 rwlocks[i].count = 0;
 434         }
 435
 436         /* Write it out (appending to end) */
 437         if (write(fd, rwlocks, size) != size) {
 438                 free(rwlocks);
 439                 return -1;
 440         }
 441         smp_machine = this_is_smp();
 442         free(rwlocks);
 443         return 0;
 444 }
 445
 446 int tdb_clear_spinlocks(TDB_CONTEXT *tdb)
 447 {
 448         tdb_rwlock_t *rwlocks;
 449         unsigned i;
 450
 451         if (tdb->header.rwlocks == 0) return 0;
 452         if (!tdb->map_ptr) return -1;
 453
 454         /* We're mmapped here */
 455         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 456         for(i = 0; i < tdb->header.hash_size+1; i++) {
 457                 __spin_lock_init(&rwlocks[i].lock);
 458                 rwlocks[i].count = 0;
 459         }
 460         return 0;
 461 }
 462 #else
 463 int tdb_create_rwlocks(int fd, unsigned int hash_size) { return 0; }
 464 int tdb_spinlock(TDB_CONTEXT *tdb, int list, int rw_type) { return -1; }
 465 int tdb_spinunlock(TDB_CONTEXT *tdb, int list, int rw_type) { return -1; }
 466
 467 /* Non-spinlock version: remove spinlock pointer */
 468 int tdb_clear_spinlocks(TDB_CONTEXT *tdb)
 469 {
 470         tdb_off off = (tdb_off)((char *)&tdb->header.rwlocks
 471                                 - (char *)&tdb->header);
 472
 473         tdb->header.rwlocks = 0;
 474         if (lseek(tdb->fd, off, SEEK_SET) != off
 475             || write(tdb->fd, (void *)&tdb->header.rwlocks,
 476                      sizeof(tdb->header.rwlocks))
 477             != sizeof(tdb->header.rwlocks))
 478                 return -1;
 479         return 0;
 480 }
 481 #endif