pppd/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 #include <stdlib.h>
  27 #include <stdio.h>
  28 #include <unistd.h>
  29 #include <string.h>
  30 #include <fcntl.h>
  31 #include <errno.h>
  32 #include <sys/stat.h>
  33 #include <time.h>
  34 #include <signal.h>
  35 #include "tdb.h"
  36 #include "spinlock.h"
  37
  38 #define DEBUG
  39
  40 #ifdef USE_SPINLOCKS
  41
  42 /*
  43  * ARCH SPECIFIC
  44  */
  45
  46 #if defined(SPARC_SPINLOCKS)
  47
  48 static inline int __spin_trylock(spinlock_t *lock)
  49 {
  50         unsigned int result;
  51
  52         asm volatile("ldstub    [%1], %0"
  53                 : "=r" (result)
  54                 : "r" (lock)
  55                 : "memory");
  56
  57         return (result == 0) ? 0 : EBUSY;
  58 }
  59
  60 static inline void __spin_unlock(spinlock_t *lock)
  61 {
  62         asm volatile("":::"memory");
  63         *lock = 0;
  64 }
  65
  66 static inline void __spin_lock_init(spinlock_t *lock)
  67 {
  68         *lock = 0;
  69 }
  70
  71 static inline int __spin_is_locked(spinlock_t *lock)
  72 {
  73         return (*lock != 0);
  74 }
  75
  76 #elif defined(POWERPC_SPINLOCKS)
  77
  78 static inline int __spin_trylock(spinlock_t *lock)
  79 {
  80         unsigned int result;
  81
  82         __asm__ __volatile__(
  83 "1:     lwarx           %0,0,%1\n\
  84         cmpwi           0,%0,0\n\
  85         li              %0,0\n\
  86         bne-            2f\n\
  87         li              %0,1\n\
  88         stwcx.          %0,0,%1\n\
  89         bne-            1b\n\
  90         isync\n\
  91 2:"     : "=&r"(result)
  92         : "r"(lock)
  93         : "cr0", "memory");
  94
  95         return (result == 1) ? 0 : EBUSY;
  96 }
  97
  98 static inline void __spin_unlock(spinlock_t *lock)
  99 {
 100         asm volatile("eieio":::"memory");
 101         *lock = 0;
 102 }
 103
 104 static inline void __spin_lock_init(spinlock_t *lock)
 105 {
 106         *lock = 0;
 107 }
 108
 109 static inline int __spin_is_locked(spinlock_t *lock)
 110 {
 111         return (*lock != 0);
 112 }
 113
 114 #elif defined(INTEL_SPINLOCKS)
 115
 116 static inline int __spin_trylock(spinlock_t *lock)
 117 {
 118         int oldval;
 119
 120         asm volatile("xchgl %0,%1"
 121                 : "=r" (oldval), "=m" (*lock)
 122                 : "0" (0)
 123                 : "memory");
 124
 125         return oldval > 0 ? 0 : EBUSY;
 126 }
 127
 128 static inline void __spin_unlock(spinlock_t *lock)
 129 {
 130         asm volatile("":::"memory");
 131         *lock = 1;
 132 }
 133
 134 static inline void __spin_lock_init(spinlock_t *lock)
 135 {
 136         *lock = 1;
 137 }
 138
 139 static inline int __spin_is_locked(spinlock_t *lock)
 140 {
 141         return (*lock != 1);
 142 }
 143
 144 #elif defined(MIPS_SPINLOCKS) && defined(sgi) && (_COMPILER_VERSION >= 730)
 145
 146 /* Implement spinlocks on IRIX using the MIPSPro atomic fetch operations. See
 147  * sync(3) for the details of the intrinsic operations.
 148  *
 149  * "sgi" and "_COMPILER_VERSION" are always defined by MIPSPro.
 150  */
 151
 152 #ifdef STANDALONE
 153
 154 /* MIPSPro 7.3 has "__inline" as an extension, but not "inline. */
 155 #define inline __inline
 156
 157 #endif /* STANDALONE */
 158
 159 /* Returns 0 if the lock is acquired, EBUSY otherwise. */
 160 static inline int __spin_trylock(spinlock_t *lock)
 161 {
 162         unsigned int val;
 163         val = __lock_test_and_set(lock, 1);
 164         return val == 0 ? 0 : EBUSY;
 165 }
 166
 167 static inline void __spin_unlock(spinlock_t *lock)
 168 {
 169         __lock_release(lock);
 170 }
 171
 172 static inline void __spin_lock_init(spinlock_t *lock)
 173 {
 174         __lock_release(lock);
 175 }
 176
 177 /* Returns 1 if the lock is held, 0 otherwise. */
 178 static inline int __spin_is_locked(spinlock_t *lock)
 179 {
 180         unsigned int val;
 181         val = __add_and_fetch(lock, 0);
 182         return val;
 183 }
 184
 185 #elif defined(MIPS_SPINLOCKS)
 186
 187 static inline unsigned int load_linked(unsigned long addr)
 188 {
 189         unsigned int res;
 190
 191         __asm__ __volatile__("ll\t%0,(%1)"
 192                 : "=r" (res)
 193                 : "r" (addr));
 194
 195         return res;
 196 }
 197
 198 static inline unsigned int store_conditional(unsigned long addr, unsigned int value)
 199 {
 200         unsigned int res;
 201
 202         __asm__ __volatile__("sc\t%0,(%2)"
 203                 : "=r" (res)
 204                 : "0" (value), "r" (addr));
 205         return res;
 206 }
 207
 208 static inline int __spin_trylock(spinlock_t *lock)
 209 {
 210         unsigned int mw;
 211
 212         do {
 213                 mw = load_linked(lock);
 214                 if (mw)
 215                         return EBUSY;
 216         } while (!store_conditional(lock, 1));
 217
 218         asm volatile("":::"memory");
 219
 220         return 0;
 221 }
 222
 223 static inline void __spin_unlock(spinlock_t *lock)
 224 {
 225         asm volatile("":::"memory");
 226         *lock = 0;
 227 }
 228
 229 static inline void __spin_lock_init(spinlock_t *lock)
 230 {
 231         *lock = 0;
 232 }
 233
 234 static inline int __spin_is_locked(spinlock_t *lock)
 235 {
 236         return (*lock != 0);
 237 }
 238
 239 #else
 240 #error Need to implement spinlock code in spinlock.c
 241 #endif
 242
 243 /*
 244  * OS SPECIFIC
 245  */
 246
 247 static void yield_cpu(void)
 248 {
 249         struct timespec tm;
 250
 251 #ifdef USE_SCHED_YIELD
 252         sched_yield();
 253 #else
 254         /* Linux will busy loop for delays < 2ms on real time tasks */
 255         tm.tv_sec = 0;
 256         tm.tv_nsec = 2000000L + 1;
 257         nanosleep(&tm, NULL);
 258 #endif
 259 }
 260
 261 static int this_is_smp(void)
 262 {
 263 #if defined(HAVE_SYSCONF) && defined(SYSCONF_SC_NPROC_ONLN)
 264         return (sysconf(_SC_NPROC_ONLN) > 1) ? 1 : 0;
 265 #else
 266         return 0;
 267 #endif
 268 }
 269
 270 /*
 271  * GENERIC
 272  */
 273
 274 static int smp_machine = 0;
 275
 276 static inline void __spin_lock(spinlock_t *lock)
 277 {
 278         int ntries = 0;
 279
 280         while(__spin_trylock(lock)) {
 281                 while(__spin_is_locked(lock)) {
 282                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 283                                 continue;
 284                         yield_cpu();
 285                 }
 286         }
 287 }
 288
 289 static void __read_lock(tdb_rwlock_t *rwlock)
 290 {
 291         int ntries = 0;
 292
 293         while(1) {
 294                 __spin_lock(&rwlock->lock);
 295
 296                 if (!(rwlock->count & RWLOCK_BIAS)) {
 297                         rwlock->count++;
 298                         __spin_unlock(&rwlock->lock);
 299                         return;
 300                 }
 301
 302                 __spin_unlock(&rwlock->lock);
 303
 304                 while(rwlock->count & RWLOCK_BIAS) {
 305                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 306                                 continue;
 307                         yield_cpu();
 308                 }
 309         }
 310 }
 311
 312 static void __write_lock(tdb_rwlock_t *rwlock)
 313 {
 314         int ntries = 0;
 315
 316         while(1) {
 317                 __spin_lock(&rwlock->lock);
 318
 319                 if (rwlock->count == 0) {
 320                         rwlock->count |= RWLOCK_BIAS;
 321                         __spin_unlock(&rwlock->lock);
 322                         return;
 323                 }
 324
 325                 __spin_unlock(&rwlock->lock);
 326
 327                 while(rwlock->count != 0) {
 328                         if (smp_machine && ntries++ < MAX_BUSY_LOOPS)
 329                                 continue;
 330                         yield_cpu();
 331                 }
 332         }
 333 }
 334
 335 static void __write_unlock(tdb_rwlock_t *rwlock)
 336 {
 337         __spin_lock(&rwlock->lock);
 338
 339 #ifdef DEBUG
 340         if (!(rwlock->count & RWLOCK_BIAS))
 341                 fprintf(stderr, "bug: write_unlock\n");
 342 #endif
 343
 344         rwlock->count &= ~RWLOCK_BIAS;
 345         __spin_unlock(&rwlock->lock);
 346 }
 347
 348 static void __read_unlock(tdb_rwlock_t *rwlock)
 349 {
 350         __spin_lock(&rwlock->lock);
 351
 352 #ifdef DEBUG
 353         if (!rwlock->count)
 354                 fprintf(stderr, "bug: read_unlock\n");
 355
 356         if (rwlock->count & RWLOCK_BIAS)
 357                 fprintf(stderr, "bug: read_unlock\n");
 358 #endif
 359
 360         rwlock->count--;
 361         __spin_unlock(&rwlock->lock);
 362 }
 363
 364 /* TDB SPECIFIC */
 365
 366 /* lock a list in the database. list -1 is the alloc list */
 367 int tdb_spinlock(TDB_CONTEXT *tdb, int list, int rw_type)
 368 {
 369         tdb_rwlock_t *rwlocks;
 370
 371         if (!tdb->map_ptr) return -1;
 372         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 373
 374         switch(rw_type) {
 375         case F_RDLCK:
 376                 __read_lock(&rwlocks[list+1]);
 377                 break;
 378
 379         case F_WRLCK:
 380                 __write_lock(&rwlocks[list+1]);
 381                 break;
 382
 383         default:
 384                 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
 385         }
 386         return 0;
 387 }
 388
 389 /* unlock the database. */
 390 int tdb_spinunlock(TDB_CONTEXT *tdb, int list, int rw_type)
 391 {
 392         tdb_rwlock_t *rwlocks;
 393
 394         if (!tdb->map_ptr) return -1;
 395         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 396
 397         switch(rw_type) {
 398         case F_RDLCK:
 399                 __read_unlock(&rwlocks[list+1]);
 400                 break;
 401
 402         case F_WRLCK:
 403                 __write_unlock(&rwlocks[list+1]);
 404                 break;
 405
 406         default:
 407                 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
 408         }
 409
 410         return 0;
 411 }
 412
 413 int tdb_create_rwlocks(int fd, unsigned int hash_size)
 414 {
 415         unsigned size, i;
 416         tdb_rwlock_t *rwlocks;
 417
 418         size = TDB_SPINLOCK_SIZE(hash_size);
 419         rwlocks = malloc(size);
 420         if (!rwlocks)
 421                 return -1;
 422
 423         for(i = 0; i < hash_size+1; i++) {
 424                 __spin_lock_init(&rwlocks[i].lock);
 425                 rwlocks[i].count = 0;
 426         }
 427
 428         /* Write it out (appending to end) */
 429         if (write(fd, rwlocks, size) != size) {
 430                 free(rwlocks);
 431                 return -1;
 432         }
 433         smp_machine = this_is_smp();
 434         free(rwlocks);
 435         return 0;
 436 }
 437
 438 int tdb_clear_spinlocks(TDB_CONTEXT *tdb)
 439 {
 440         tdb_rwlock_t *rwlocks;
 441         unsigned i;
 442
 443         if (tdb->header.rwlocks == 0) return 0;
 444         if (!tdb->map_ptr) return -1;
 445
 446         /* We're mmapped here */
 447         rwlocks = (tdb_rwlock_t *)((char *)tdb->map_ptr + tdb->header.rwlocks);
 448         for(i = 0; i < tdb->header.hash_size+1; i++) {
 449                 __spin_lock_init(&rwlocks[i].lock);
 450                 rwlocks[i].count = 0;
 451         }
 452         return 0;
 453 }
 454 #else
 455 int tdb_create_rwlocks(int fd, unsigned int hash_size) { return 0; }
 456 int tdb_spinlock(TDB_CONTEXT *tdb, int list, int rw_type) { return -1; }
 457 int tdb_spinunlock(TDB_CONTEXT *tdb, int list, int rw_type) { return -1; }
 458
 459 /* Non-spinlock version: remove spinlock pointer */
 460 int tdb_clear_spinlocks(TDB_CONTEXT *tdb)
 461 {
 462         tdb_off off = (tdb_off)((char *)&tdb->header.rwlocks
 463                                 - (char *)&tdb->header);
 464
 465         tdb->header.rwlocks = 0;
 466         if (lseek(tdb->fd, off, SEEK_SET) != off
 467             || write(tdb->fd, (void *)&tdb->header.rwlocks,
 468                      sizeof(tdb->header.rwlocks))
 469             != sizeof(tdb->header.rwlocks))
 470                 return -1;
 471         return 0;
 472 }
 473 #endif