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 #define _KLIBC_HAS_ARCH_SIG_ATOMIC_T
  32 #include <stdlib.h>
  33 #include <stdio.h>
  34 #include <unistd.h>
  35 #include <string.h>
  36 #include <fcntl.h>
  37 #include <errno.h>
  38 #include <sys/stat.h>
  39 #include <time.h>
  40 #include <signal.h>
  41 #include "tdb.h"
  42 #include "spinlock.h"
  43
  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         if (!(rwlock->count & RWLOCK_BIAS))
 303                 dbg("bug: write_unlock");
 304
 305         rwlock->count &= ~RWLOCK_BIAS;
 306         __spin_unlock(&rwlock->lock);
 307 }
 308
 309 static void __read_unlock(tdb_rwlock_t *rwlock)
 310 {
 311         __spin_lock(&rwlock->lock);
 312
 313         if (!rwlock->count)
 314                 dbg("bug: read_unlock");
 315
 316         if (rwlock->count & RWLOCK_BIAS)
 317                 dbg("bug: read_unlock");
 318
 319         rwlock->count--;
 320         __spin_unlock(&rwlock->lock);
 321 }
 322
 323 /* TDB SPECIFIC */
 324
 325 /* lock a list in the database. list -1 is the alloc list */
 326 int tdb_spinlock(TDB_CONTEXT *tdb, int list, int rw_type)
 327 {
 328         tdb_rwlock_t *rwlocks;
 329
 330         if (!tdb->map_ptr) return -1;
 331         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 332
 333         switch(rw_type) {
 334         case F_RDLCK:
 335                 __read_lock(&rwlocks[list+1]);
 336                 break;
 337
 338         case F_WRLCK:
 339                 __write_lock(&rwlocks[list+1]);
 340                 break;
 341
 342         default:
 343                 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
 344         }
 345         return 0;
 346 }
 347
 348 /* unlock the database. */
 349 int tdb_spinunlock(TDB_CONTEXT *tdb, int list, int rw_type)
 350 {
 351         tdb_rwlock_t *rwlocks;
 352
 353         if (!tdb->map_ptr) return -1;
 354         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 355
 356         switch(rw_type) {
 357         case F_RDLCK:
 358                 __read_unlock(&rwlocks[list+1]);
 359                 break;
 360
 361         case F_WRLCK:
 362                 __write_unlock(&rwlocks[list+1]);
 363                 break;
 364
 365         default:
 366                 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
 367         }
 368
 369         return 0;
 370 }
 371
 372 int tdb_create_rwlocks(int fd, unsigned int hash_size)
 373 {
 374         unsigned size, i;
 375         tdb_rwlock_t *rwlocks;
 376
 377         size = (hash_size + 1) * sizeof(tdb_rwlock_t);
 378         rwlocks = malloc(size);
 379         if (!rwlocks)
 380                 return -1;
 381
 382         for(i = 0; i < hash_size+1; i++) {
 383                 __spin_lock_init(&rwlocks[i].lock);
 384                 rwlocks[i].count = 0;
 385         }
 386
 387         /* Write it out (appending to end) */
 388         if (write(fd, rwlocks, size) != size) {
 389                 free(rwlocks);
 390                 return -1;
 391         }
 392         smp_machine = this_is_smp();
 393         free(rwlocks);
 394         return 0;
 395 }
 396
 397 int tdb_clear_spinlocks(TDB_CONTEXT *tdb)
 398 {
 399         tdb_rwlock_t *rwlocks;
 400         unsigned i;
 401
 402         if (tdb->header.rwlocks == 0) return 0;
 403         if (!tdb->map_ptr) return -1;
 404
 405         /* We're mmapped here */
 406         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 407         for(i = 0; i < tdb->header.hash_size+1; i++) {
 408                 __spin_lock_init(&rwlocks[i].lock);
 409                 rwlocks[i].count = 0;
 410         }
 411         return 0;
 412 }
 413 #else
 414 int tdb_create_rwlocks(int fd, unsigned int hash_size) { return 0; }
 415 int tdb_spinlock(TDB_CONTEXT *tdb, int list, int rw_type) { return -1; }
 416 int tdb_spinunlock(TDB_CONTEXT *tdb, int list, int rw_type) { return -1; }
 417
 418 /* Non-spinlock version: remove spinlock pointer */
 419 int tdb_clear_spinlocks(TDB_CONTEXT *tdb)
 420 {
 421         tdb_off off = (tdb_off)((char *)&tdb->header.rwlocks
 422                                 - (char *)&tdb->header);
 423
 424         tdb->header.rwlocks = 0;
 425         if (lseek(tdb->fd, off, SEEK_SET) != off
 426             || write(tdb->fd, (void *)&tdb->header.rwlocks,
 427                      sizeof(tdb->header.rwlocks))
 428             != sizeof(tdb->header.rwlocks))
 429                 return -1;
 430         return 0;
 431 }
 432 #endif