libatalk/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 #define STANDALONE 1
  21
  22 #if HAVE_CONFIG_H
  23 #include <config.h>
  24 #endif
  25
  26 #if STANDALONE
  27 #include <stdlib.h>
  28 #include <stdio.h>
  29 #include <unistd.h>
  30 #include <string.h>
  31 #include <fcntl.h>
  32 #include <errno.h>
  33 #include <sys/stat.h>
  34 #include <time.h>
  35 #include <signal.h>
  36 #include "spinlock.h"
  37
  38 #define DEBUG
  39 #else
  40 #include "includes.h"
  41 #endif
  42
  43 #ifdef USE_SPINLOCKS
  44
  45 /*
  46  * ARCH SPECIFIC
  47  */
  48
  49 #if defined(SPARC_SPINLOCKS)
  50
  51 static inline int __spin_trylock(spinlock_t *lock)
  52 {
  53         unsigned int result;
  54
  55         asm volatile("ldstub    [%1], %0"
  56                 : "=r" (result)
  57                 : "r" (lock)
  58                 : "memory");
  59
  60         return (result == 0) ? 0 : EBUSY;
  61 }
  62
  63 static inline void __spin_unlock(spinlock_t *lock)
  64 {
  65         asm volatile("":::"memory");
  66         *lock = 0;
  67 }
  68
  69 static inline void __spin_lock_init(spinlock_t *lock)
  70 {
  71         *lock = 0;
  72 }
  73
  74 static inline int __spin_is_locked(spinlock_t *lock)
  75 {
  76         return (*lock != 0);
  77 }
  78
  79 #elif defined(POWERPC_SPINLOCKS)
  80
  81 static inline int __spin_trylock(spinlock_t *lock)
  82 {
  83         unsigned int result;
  84
  85         __asm__ __volatile__(
  86 "1:     lwarx           %0,0,%1\n\
  87         cmpwi           0,%0,0\n\
  88         li              %0,0\n\
  89         bne-            2f\n\
  90         li              %0,1\n\
  91         stwcx.          %0,0,%1\n\
  92         bne-            1b\n\
  93         isync\n\
  94 2:"     : "=&r"(result)
  95         : "r"(lock)
  96         : "cr0", "memory");
  97
  98         return (result == 1) ? 0 : EBUSY;
  99 }
 100
 101 static inline void __spin_unlock(spinlock_t *lock)
 102 {
 103         asm volatile("eieio":::"memory");
 104         *lock = 0;
 105 }
 106
 107 static inline void __spin_lock_init(spinlock_t *lock)
 108 {
 109         *lock = 0;
 110 }
 111
 112 static inline int __spin_is_locked(spinlock_t *lock)
 113 {
 114         return (*lock != 0);
 115 }
 116
 117 #elif defined(INTEL_SPINLOCKS)
 118
 119 static inline int __spin_trylock(spinlock_t *lock)
 120 {
 121         int oldval;
 122
 123         asm volatile("xchgl %0,%1"
 124                 : "=r" (oldval), "=m" (*lock)
 125                 : "0" (0)
 126                 : "memory");
 127
 128         return oldval > 0 ? 0 : EBUSY;
 129 }
 130
 131 static inline void __spin_unlock(spinlock_t *lock)
 132 {
 133         asm volatile("":::"memory");
 134         *lock = 1;
 135 }
 136
 137 static inline void __spin_lock_init(spinlock_t *lock)
 138 {
 139         *lock = 1;
 140 }
 141
 142 static inline int __spin_is_locked(spinlock_t *lock)
 143 {
 144         return (*lock != 1);
 145 }
 146
 147 #elif defined(MIPS_SPINLOCKS)
 148
 149 static inline unsigned int load_linked(unsigned long addr)
 150 {
 151         unsigned int res;
 152
 153         __asm__ __volatile__("ll\t%0,(%1)"
 154                 : "=r" (res)
 155                 : "r" (addr));
 156
 157         return res;
 158 }
 159
 160 static inline unsigned int store_conditional(unsigned long addr, unsigned int value)
 161 {
 162         unsigned int res;
 163
 164         __asm__ __volatile__("sc\t%0,(%2)"
 165                 : "=r" (res)
 166                 : "0" (value), "r" (addr));
 167         return res;
 168 }
 169
 170 static inline int __spin_trylock(spinlock_t *lock)
 171 {
 172         unsigned int mw;
 173
 174         do {
 175                 mw = load_linked(lock);
 176                 if (mw)
 177                         return EBUSY;
 178         } while (!store_conditional(lock, 1));
 179
 180         asm volatile("":::"memory");
 181
 182         return 0;
 183 }
 184
 185 static inline void __spin_unlock(spinlock_t *lock)
 186 {
 187         asm volatile("":::"memory");
 188         *lock = 0;
 189 }
 190
 191 static inline void __spin_lock_init(spinlock_t *lock)
 192 {
 193         *lock = 0;
 194 }
 195
 196 static inline int __spin_is_locked(spinlock_t *lock)
 197 {
 198         return (*lock != 0);
 199 }
 200
 201 #else
 202 #error Need to implement spinlock code in spinlock.c
 203 #endif
 204
 205 /*
 206  * OS SPECIFIC
 207  */
 208
 209 static void yield_cpu(void)
 210 {
 211         struct timespec tm;
 212
 213 #ifdef USE_SCHED_YIELD
 214         sched_yield();
 215 #else
 216         /* Linux will busy loop for delays < 2ms on real time tasks */
 217         tm.tv_sec = 0;
 218         tm.tv_nsec = 2000000L + 1;
 219         nanosleep(&tm, NULL);
 220 #endif
 221 }
 222
 223 static int this_is_smp(void)
 224 {
 225         return 0;
 226 }
 227
 228 /*
 229  * GENERIC
 230  */
 231
 232 static int smp_machine = 0;
 233
 234 static inline void __spin_lock(spinlock_t *lock)
 235 {
 236         int ntries = 0;
 237
 238         while(__spin_trylock(lock)) {
 239                 while(__spin_is_locked(lock)) {
 240                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 241                                 continue;
 242                         yield_cpu();
 243                 }
 244         }
 245 }
 246
 247 static void __read_lock(tdb_rwlock_t *rwlock)
 248 {
 249         int ntries = 0;
 250
 251         while(1) {
 252                 __spin_lock(&rwlock->lock);
 253
 254                 if (!(rwlock->count & RWLOCK_BIAS)) {
 255                         rwlock->count++;
 256                         __spin_unlock(&rwlock->lock);
 257                         return;
 258                 }
 259
 260                 __spin_unlock(&rwlock->lock);
 261
 262                 while(rwlock->count & RWLOCK_BIAS) {
 263                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 264                                 continue;
 265                         yield_cpu();
 266                 }
 267         }
 268 }
 269
 270 static void __write_lock(tdb_rwlock_t *rwlock)
 271 {
 272         int ntries = 0;
 273
 274         while(1) {
 275                 __spin_lock(&rwlock->lock);
 276
 277                 if (rwlock->count == 0) {
 278                         rwlock->count |= RWLOCK_BIAS;
 279                         __spin_unlock(&rwlock->lock);
 280                         return;
 281                 }
 282
 283                 __spin_unlock(&rwlock->lock);
 284
 285                 while(rwlock->count != 0) {
 286                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 287                                 continue;
 288                         yield_cpu();
 289                 }
 290         }
 291 }
 292
 293 static void __write_unlock(tdb_rwlock_t *rwlock)
 294 {
 295         __spin_lock(&rwlock->lock);
 296
 297 #ifdef DEBUG
 298         if (!(rwlock->count & RWLOCK_BIAS))
 299                 fprintf(stderr, "bug: write_unlock\n");
 300 #endif
 301
 302         rwlock->count &= ~RWLOCK_BIAS;
 303         __spin_unlock(&rwlock->lock);
 304 }
 305
 306 static void __read_unlock(tdb_rwlock_t *rwlock)
 307 {
 308         __spin_lock(&rwlock->lock);
 309
 310 #ifdef DEBUG
 311         if (!rwlock->count)
 312                 fprintf(stderr, "bug: read_unlock\n");
 313
 314         if (rwlock->count & RWLOCK_BIAS)
 315                 fprintf(stderr, "bug: read_unlock\n");
 316 #endif
 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