source3/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 #ifdef 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 #ifdef 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 /*
 270  * GENERIC
 271  */
 272
 273 static int smp_machine = 0;
 274
 275 static inline void __spin_lock(spinlock_t *lock)
 276 {
 277         int ntries = 0;
 278
 279         while(__spin_trylock(lock)) {
 280                 while(__spin_is_locked(lock)) {
 281                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 282                                 continue;
 283                         yield_cpu();
 284                 }
 285         }
 286 }
 287
 288 static void __read_lock(tdb_rwlock_t *rwlock)
 289 {
 290         int ntries = 0;
 291
 292         while(1) {
 293                 __spin_lock(&rwlock->lock);
 294
 295                 if (!(rwlock->count & RWLOCK_BIAS)) {
 296                         rwlock->count++;
 297                         __spin_unlock(&rwlock->lock);
 298                         return;
 299                 }
 300
 301                 __spin_unlock(&rwlock->lock);
 302
 303                 while(rwlock->count & RWLOCK_BIAS) {
 304                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 305                                 continue;
 306                         yield_cpu();
 307                 }
 308         }
 309 }
 310
 311 static void __write_lock(tdb_rwlock_t *rwlock)
 312 {
 313         int ntries = 0;
 314
 315         while(1) {
 316                 __spin_lock(&rwlock->lock);
 317
 318                 if (rwlock->count == 0) {
 319                         rwlock->count |= RWLOCK_BIAS;
 320                         __spin_unlock(&rwlock->lock);
 321                         return;
 322                 }
 323
 324                 __spin_unlock(&rwlock->lock);
 325
 326                 while(rwlock->count != 0) {
 327                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 328                                 continue;
 329                         yield_cpu();
 330                 }
 331         }
 332 }
 333
 334 static void __write_unlock(tdb_rwlock_t *rwlock)
 335 {
 336         __spin_lock(&rwlock->lock);
 337
 338 #ifdef DEBUG
 339         if (!(rwlock->count & RWLOCK_BIAS))
 340                 fprintf(stderr, "bug: write_unlock\n");
 341 #endif
 342
 343         rwlock->count &= ~RWLOCK_BIAS;
 344         __spin_unlock(&rwlock->lock);
 345 }
 346
 347 static void __read_unlock(tdb_rwlock_t *rwlock)
 348 {
 349         __spin_lock(&rwlock->lock);
 350
 351 #ifdef DEBUG
 352         if (!rwlock->count)
 353                 fprintf(stderr, "bug: read_unlock\n");
 354
 355         if (rwlock->count & RWLOCK_BIAS)
 356                 fprintf(stderr, "bug: read_unlock\n");
 357 #endif
 358
 359         rwlock->count--;
 360         __spin_unlock(&rwlock->lock);
 361 }
 362
 363 /* TDB SPECIFIC */
 364
 365 /* lock a list in the database. list -1 is the alloc list */
 366 int tdb_spinlock(TDB_CONTEXT *tdb, int list, int rw_type)
 367 {
 368         tdb_rwlock_t *rwlocks;
 369
 370         if (!tdb->map_ptr) return -1;
 371         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 372
 373         switch(rw_type) {
 374         case F_RDLCK:
 375                 __read_lock(&rwlocks[list+1]);
 376                 break;
 377
 378         case F_WRLCK:
 379                 __write_lock(&rwlocks[list+1]);
 380                 break;
 381
 382         default:
 383                 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
 384         }
 385         return 0;
 386 }
 387
 388 /* unlock the database. */
 389 int tdb_spinunlock(TDB_CONTEXT *tdb, int list, int rw_type)
 390 {
 391         tdb_rwlock_t *rwlocks;
 392
 393         if (!tdb->map_ptr) return -1;
 394         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 395
 396         switch(rw_type) {
 397         case F_RDLCK:
 398                 __read_unlock(&rwlocks[list+1]);
 399                 break;
 400
 401         case F_WRLCK:
 402                 __write_unlock(&rwlocks[list+1]);
 403                 break;
 404
 405         default:
 406                 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
 407         }
 408
 409         return 0;
 410 }
 411
 412 int tdb_create_rwlocks(int fd, unsigned int hash_size)
 413 {
 414         unsigned size, i;
 415         tdb_rwlock_t *rwlocks;
 416
 417         size = TDB_SPINLOCK_SIZE(hash_size);
 418         rwlocks = malloc(size);
 419         if (!rwlocks)
 420                 return -1;
 421
 422         for(i = 0; i < hash_size+1; i++) {
 423                 __spin_lock_init(&rwlocks[i].lock);
 424                 rwlocks[i].count = 0;
 425         }
 426
 427         /* Write it out (appending to end) */
 428         if (write(fd, rwlocks, size) != size) {
 429                 free(rwlocks);
 430                 return -1;
 431         }
 432         smp_machine = this_is_smp();
 433         free(rwlocks);
 434         return 0;
 435 }
 436
 437 int tdb_clear_spinlocks(TDB_CONTEXT *tdb)
 438 {
 439         tdb_rwlock_t *rwlocks;
 440         unsigned i;
 441
 442         if (tdb->header.rwlocks == 0) return 0;
 443         if (!tdb->map_ptr) return -1;
 444
 445         /* We're mmapped here */
 446         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 447         for(i = 0; i < tdb->header.hash_size+1; i++) {
 448                 __spin_lock_init(&rwlocks[i].lock);
 449                 rwlocks[i].count = 0;
 450         }
 451         return 0;
 452 }
 453 #else
 454 int tdb_create_rwlocks(int fd, unsigned int hash_size) { return 0; }
 455 int tdb_spinlock(TDB_CONTEXT *tdb, int list, int rw_type) { return -1; }
 456 int tdb_spinunlock(TDB_CONTEXT *tdb, int list, int rw_type) { return -1; }
 457
 458 /* Non-spinlock version: remove spinlock pointer */
 459 int tdb_clear_spinlocks(TDB_CONTEXT *tdb)
 460 {
 461         tdb_off off = (tdb_off)((char *)&tdb->header.rwlocks
 462                                 - (char *)&tdb->header);
 463
 464         tdb->header.rwlocks = 0;
 465         if (lseek(tdb->fd, off, SEEK_SET) != off
 466             || write(tdb->fd, (void *)&tdb->header.rwlocks,
 467                      sizeof(tdb->header.rwlocks))
 468             != sizeof(tdb->header.rwlocks))
 469                 return -1;
 470         return 0;
 471 }
 472 #endif