nptl/pthread_mutex_lock.c

   1 /* Copyright (C) 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <assert.h>
  21 #include <errno.h>
  22 #include <stdlib.h>
  23 #include <unistd.h>
  24 #include <not-cancel.h>
  25 #include "pthreadP.h"
  26 #include <lowlevellock.h>
  27
  28
  29 #ifndef LLL_MUTEX_LOCK
  30 # define LLL_MUTEX_LOCK(mutex) lll_mutex_lock (mutex)
  31 # define LLL_MUTEX_TRYLOCK(mutex) lll_mutex_trylock (mutex)
  32 # define LLL_ROBUST_MUTEX_LOCK(mutex, id) lll_robust_mutex_lock (mutex, id)
  33 #endif
  34
  35
  36 int
  37 __pthread_mutex_lock (mutex)
  38      pthread_mutex_t *mutex;
  39 {
  40   assert (sizeof (mutex->__size) >= sizeof (mutex->__data));
  41
  42   int oldval;
  43   pid_t id = THREAD_GETMEM (THREAD_SELF, tid);
  44
  45   int retval = 0;
  46   switch (__builtin_expect (mutex->__data.__kind, PTHREAD_MUTEX_TIMED_NP))
  47     {
  48       /* Recursive mutex.  */
  49     case PTHREAD_MUTEX_RECURSIVE_NP:
  50       /* Check whether we already hold the mutex.  */
  51       if (mutex->__data.__owner == id)
  52         {
  53           /* Just bump the counter.  */
  54           if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
  55             /* Overflow of the counter.  */
  56             return EAGAIN;
  57
  58           ++mutex->__data.__count;
  59
  60           return 0;
  61         }
  62
  63       /* We have to get the mutex.  */
  64       LLL_MUTEX_LOCK (mutex->__data.__lock);
  65
  66       assert (mutex->__data.__owner == 0);
  67       mutex->__data.__count = 1;
  68       break;
  69
  70       /* Error checking mutex.  */
  71     case PTHREAD_MUTEX_ERRORCHECK_NP:
  72       /* Check whether we already hold the mutex.  */
  73       if (__builtin_expect (mutex->__data.__owner == id, 0))
  74         return EDEADLK;
  75
  76       /* FALLTHROUGH */
  77
  78     case PTHREAD_MUTEX_TIMED_NP:
  79     simple:
  80       /* Normal mutex.  */
  81       LLL_MUTEX_LOCK (mutex->__data.__lock);
  82       assert (mutex->__data.__owner == 0);
  83       break;
  84
  85     case PTHREAD_MUTEX_ADAPTIVE_NP:
  86       if (! __is_smp)
  87         goto simple;
  88
  89       if (LLL_MUTEX_TRYLOCK (mutex->__data.__lock) != 0)
  90         {
  91           int cnt = 0;
  92           int max_cnt = MIN (MAX_ADAPTIVE_COUNT,
  93                              mutex->__data.__spins * 2 + 10);
  94           do
  95             {
  96               if (cnt++ >= max_cnt)
  97                 {
  98                   LLL_MUTEX_LOCK (mutex->__data.__lock);
  99                   break;
 100                 }
 101
 102 #ifdef BUSY_WAIT_NOP
 103               BUSY_WAIT_NOP;
 104 #endif
 105             }
 106           while (LLL_MUTEX_TRYLOCK (mutex->__data.__lock) != 0);
 107
 108           mutex->__data.__spins += (cnt - mutex->__data.__spins) / 8;
 109         }
 110       assert (mutex->__data.__owner == 0);
 111       break;
 112
 113     case PTHREAD_MUTEX_ROBUST_RECURSIVE_NP:
 114     case PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP:
 115     case PTHREAD_MUTEX_ROBUST_NORMAL_NP:
 116     case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP:
 117       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 118                      &mutex->__data.__list.__next);
 119
 120       oldval = mutex->__data.__lock;
 121       do
 122         {
 123         again:
 124           if ((oldval & FUTEX_OWNER_DIED) != 0)
 125             {
 126               /* The previous owner died.  Try locking the mutex.  */
 127               int newval = id;
 128 #ifdef NO_INCR
 129               newval |= FUTEX_WAITERS;
 130 #endif
 131
 132               newval
 133                 = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 134                                                        newval, oldval);
 135
 136               if (newval != oldval)
 137                 {
 138                   oldval = newval;
 139                   goto again;
 140                 }
 141
 142               /* We got the mutex.  */
 143               mutex->__data.__count = 1;
 144               /* But it is inconsistent unless marked otherwise.  */
 145               mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 146
 147               ENQUEUE_MUTEX (mutex);
 148               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 149
 150               /* Note that we deliberately exit here.  If we fall
 151                  through to the end of the function __nusers would be
 152                  incremented which is not correct because the old
 153                  owner has to be discounted.  If we are not supposed
 154                  to increment __nusers we actually have to decrement
 155                  it here.  */
 156 #ifdef NO_INCR
 157               --mutex->__data.__nusers;
 158 #endif
 159
 160               return EOWNERDEAD;
 161             }
 162
 163           /* Check whether we already hold the mutex.  */
 164           if (__builtin_expect ((oldval & FUTEX_TID_MASK) == id, 0))
 165             {
 166               if (mutex->__data.__kind
 167                   == PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP)
 168                 {
 169                   THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 170                                  NULL);
 171                   return EDEADLK;
 172                 }
 173
 174               if (mutex->__data.__kind
 175                   == PTHREAD_MUTEX_ROBUST_RECURSIVE_NP)
 176                 {
 177                   THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 178                                  NULL);
 179
 180                   /* Just bump the counter.  */
 181                   if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 182                     /* Overflow of the counter.  */
 183                     return EAGAIN;
 184
 185                   ++mutex->__data.__count;
 186
 187                   return 0;
 188                 }
 189             }
 190
 191           oldval = LLL_ROBUST_MUTEX_LOCK (mutex->__data.__lock, id);
 192
 193           if (__builtin_expect (mutex->__data.__owner
 194                                 == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 195             {
 196               /* This mutex is now not recoverable.  */
 197               mutex->__data.__count = 0;
 198               lll_mutex_unlock (mutex->__data.__lock);
 199               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 200               return ENOTRECOVERABLE;
 201             }
 202         }
 203       while ((oldval & FUTEX_OWNER_DIED) != 0);
 204
 205       mutex->__data.__count = 1;
 206       ENQUEUE_MUTEX (mutex);
 207       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 208       break;
 209
 210     case PTHREAD_MUTEX_PI_RECURSIVE_NP:
 211     case PTHREAD_MUTEX_PI_ERRORCHECK_NP:
 212     case PTHREAD_MUTEX_PI_NORMAL_NP:
 213     case PTHREAD_MUTEX_PI_ADAPTIVE_NP:
 214     case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP:
 215     case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP:
 216     case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:
 217     case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP:
 218       {
 219         int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP;
 220         int robust = mutex->__data.__kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP;
 221
 222         if (robust)
 223           /* Note: robust PI futexes are signaled by setting bit 0.  */
 224           THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 225                          (void *) (((uintptr_t) &mutex->__data.__list.__next)
 226                                    | 1));
 227
 228         oldval = mutex->__data.__lock;
 229
 230         /* Check whether we already hold the mutex.  */
 231         if (__builtin_expect ((oldval & FUTEX_TID_MASK) == id, 0))
 232           {
 233             if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
 234               {
 235                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 236                 return EDEADLK;
 237               }
 238
 239             if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
 240               {
 241                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 242
 243                 /* Just bump the counter.  */
 244                 if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 245                   /* Overflow of the counter.  */
 246                   return EAGAIN;
 247
 248                 ++mutex->__data.__count;
 249
 250                 return 0;
 251               }
 252           }
 253
 254         int newval = id;
 255 #ifdef NO_INCR
 256         newval |= FUTEX_WAITERS;
 257 #endif
 258         oldval = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 259                                                       newval, 0);
 260
 261         if (oldval != 0)
 262           {
 263             /* The mutex is locked.  The kernel will now take care of
 264                everything.  */
 265             INTERNAL_SYSCALL_DECL (__err);
 266             int e = INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 267                                       FUTEX_LOCK_PI, 1, 0);
 268
 269             if (INTERNAL_SYSCALL_ERROR_P (e, __err)
 270                 && (INTERNAL_SYSCALL_ERRNO (e, __err) == ESRCH
 271                     || INTERNAL_SYSCALL_ERRNO (e, __err) == EDEADLK))
 272               {
 273                 assert (INTERNAL_SYSCALL_ERRNO (e, __err) != EDEADLK
 274                         || (kind != PTHREAD_MUTEX_ERRORCHECK_NP
 275                             && kind != PTHREAD_MUTEX_RECURSIVE_NP));
 276                 /* ESRCH can happen only for non-robust PI mutexes where
 277                    the owner of the lock died.  */
 278                 assert (INTERNAL_SYSCALL_ERRNO (e, __err) != ESRCH || !robust);
 279
 280                 /* Delay the thread indefinitely.  */
 281                 while (1)
 282                   pause_not_cancel ();
 283               }
 284
 285             oldval = mutex->__data.__lock;
 286
 287             assert (robust || (oldval & FUTEX_OWNER_DIED) == 0);
 288           }
 289
 290         if (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0))
 291           {
 292             atomic_and (&mutex->__data.__lock, ~FUTEX_OWNER_DIED);
 293
 294             /* We got the mutex.  */
 295             mutex->__data.__count = 1;
 296             /* But it is inconsistent unless marked otherwise.  */
 297             mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 298
 299             ENQUEUE_MUTEX_PI (mutex);
 300             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 301
 302             /* Note that we deliberately exit here.  If we fall
 303                through to the end of the function __nusers would be
 304                incremented which is not correct because the old owner
 305                has to be discounted.  If we are not supposed to
 306                increment __nusers we actually have to decrement it here.  */
 307 #ifdef NO_INCR
 308             --mutex->__data.__nusers;
 309 #endif
 310
 311             return EOWNERDEAD;
 312           }
 313
 314         if (robust
 315             && __builtin_expect (mutex->__data.__owner
 316                                  == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 317           {
 318             /* This mutex is now not recoverable.  */
 319             mutex->__data.__count = 0;
 320
 321             INTERNAL_SYSCALL_DECL (__err);
 322             INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 323                               FUTEX_UNLOCK_PI, 0, 0);
 324
 325             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 326             return ENOTRECOVERABLE;
 327           }
 328
 329         mutex->__data.__count = 1;
 330         if (robust)
 331           {
 332             ENQUEUE_MUTEX_PI (mutex);
 333             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 334           }
 335       }
 336       break;
 337
 338     case PTHREAD_MUTEX_PP_RECURSIVE_NP:
 339     case PTHREAD_MUTEX_PP_ERRORCHECK_NP:
 340     case PTHREAD_MUTEX_PP_NORMAL_NP:
 341     case PTHREAD_MUTEX_PP_ADAPTIVE_NP:
 342       {
 343         int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP;
 344
 345         oldval = mutex->__data.__lock;
 346
 347         /* Check whether we already hold the mutex.  */
 348         if (mutex->__data.__owner == id)
 349           {
 350             if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
 351               return EDEADLK;
 352
 353             if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
 354               {
 355                 /* Just bump the counter.  */
 356                 if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 357                   /* Overflow of the counter.  */
 358                   return EAGAIN;
 359
 360                 ++mutex->__data.__count;
 361
 362                 return 0;
 363               }
 364           }
 365
 366         int oldprio = -1, ceilval;
 367         do
 368           {
 369             int ceiling = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK)
 370                           >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 371
 372             if (__pthread_current_priority () > ceiling)
 373               {
 374                 if (oldprio != -1)
 375                   __pthread_tpp_change_priority (oldprio, -1);
 376                 return EINVAL;
 377               }
 378
 379             retval = __pthread_tpp_change_priority (oldprio, ceiling);
 380             if (retval)
 381               return retval;
 382
 383             ceilval = ceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 384             oldprio = ceiling;
 385
 386             oldval
 387               = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 388 #ifdef NO_INCR
 389                                                      ceilval | 2,
 390 #else
 391                                                      ceilval | 1,
 392 #endif
 393                                                      ceilval);
 394
 395             if (oldval == ceilval)
 396               break;
 397
 398             do
 399               {
 400                 oldval
 401                   = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 402                                                          ceilval | 2,
 403                                                          ceilval | 1);
 404
 405                 if ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval)
 406                   break;
 407
 408                 if (oldval != ceilval)
 409                   lll_futex_wait (&mutex->__data.__lock, ceilval | 2);
 410               }
 411             while (atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 412                                                         ceilval | 2, ceilval)
 413                    != ceilval);
 414           }
 415         while ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval);
 416
 417         assert (mutex->__data.__owner == 0);
 418         mutex->__data.__count = 1;
 419       }
 420       break;
 421
 422     default:
 423       /* Correct code cannot set any other type.  */
 424       return EINVAL;
 425     }
 426
 427   /* Record the ownership.  */
 428   mutex->__data.__owner = id;
 429 #ifndef NO_INCR
 430   ++mutex->__data.__nusers;
 431 #endif
 432
 433   return retval;
 434 }
 435 #ifndef __pthread_mutex_lock
 436 strong_alias (__pthread_mutex_lock, pthread_mutex_lock)
 437 strong_alias (__pthread_mutex_lock, __pthread_mutex_lock_internal)
 438 #endif