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