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 "pthreadP.h"
  24 #include <lowlevellock.h>
  25
  26
  27 #ifndef LLL_MUTEX_LOCK
  28 # define LLL_MUTEX_LOCK(mutex) lll_mutex_lock (mutex)
  29 # define LLL_MUTEX_TRYLOCK(mutex) lll_mutex_trylock (mutex)
  30 # define LLL_ROBUST_MUTEX_LOCK(mutex, id) lll_robust_mutex_lock (mutex, id)
  31 #endif
  32
  33
  34 int
  35 __pthread_mutex_lock (mutex)
  36      pthread_mutex_t *mutex;
  37 {
  38   assert (sizeof (mutex->__size) >= sizeof (mutex->__data));
  39
  40   int oldval;
  41   pid_t id = THREAD_GETMEM (THREAD_SELF, tid);
  42
  43   int retval = 0;
  44   switch (__builtin_expect (mutex->__data.__kind, PTHREAD_MUTEX_TIMED_NP))
  45     {
  46       /* Recursive mutex.  */
  47     case PTHREAD_MUTEX_RECURSIVE_NP:
  48       /* Check whether we already hold the mutex.  */
  49       if (mutex->__data.__owner == id)
  50         {
  51           /* Just bump the counter.  */
  52           if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
  53             /* Overflow of the counter.  */
  54             return EAGAIN;
  55
  56           ++mutex->__data.__count;
  57
  58           return 0;
  59         }
  60
  61       /* We have to get the mutex.  */
  62       LLL_MUTEX_LOCK (mutex->__data.__lock);
  63
  64       assert (mutex->__data.__owner == 0);
  65       mutex->__data.__count = 1;
  66       break;
  67
  68       /* Error checking mutex.  */
  69     case PTHREAD_MUTEX_ERRORCHECK_NP:
  70       /* Check whether we already hold the mutex.  */
  71       if (__builtin_expect (mutex->__data.__owner == id, 0))
  72         return EDEADLK;
  73
  74       /* FALLTHROUGH */
  75
  76     case PTHREAD_MUTEX_TIMED_NP:
  77     simple:
  78       /* Normal mutex.  */
  79       LLL_MUTEX_LOCK (mutex->__data.__lock);
  80       assert (mutex->__data.__owner == 0);
  81       break;
  82
  83     case PTHREAD_MUTEX_ADAPTIVE_NP:
  84       if (! __is_smp)
  85         goto simple;
  86
  87       if (LLL_MUTEX_TRYLOCK (mutex->__data.__lock) != 0)
  88         {
  89           int cnt = 0;
  90           int max_cnt = MIN (MAX_ADAPTIVE_COUNT,
  91                              mutex->__data.__spins * 2 + 10);
  92           do
  93             {
  94               if (cnt++ >= max_cnt)
  95                 {
  96                   LLL_MUTEX_LOCK (mutex->__data.__lock);
  97                   break;
  98                 }
  99
 100 #ifdef BUSY_WAIT_NOP
 101               BUSY_WAIT_NOP;
 102 #endif
 103             }
 104           while (LLL_MUTEX_TRYLOCK (mutex->__data.__lock) != 0);
 105
 106           mutex->__data.__spins += (cnt - mutex->__data.__spins) / 8;
 107         }
 108       assert (mutex->__data.__owner == 0);
 109       break;
 110
 111     case PTHREAD_MUTEX_ROBUST_PRIVATE_RECURSIVE_NP:
 112     case PTHREAD_MUTEX_ROBUST_PRIVATE_ERRORCHECK_NP:
 113     case PTHREAD_MUTEX_ROBUST_PRIVATE_NP:
 114     case PTHREAD_MUTEX_ROBUST_PRIVATE_ADAPTIVE_NP:
 115       oldval = mutex->__data.__lock;
 116       do
 117         {
 118           if ((oldval & FUTEX_OWNER_DIED) != 0)
 119             {
 120               /* The previous owner died.  Try locking the mutex.  */
 121               int newval;
 122               while ((newval
 123                       = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 124                                                              id, oldval))
 125                      != oldval)
 126                 {
 127                   if ((newval & FUTEX_OWNER_DIED) == 0)
 128                     goto normal;
 129                   oldval = newval;
 130                 }
 131
 132               /* We got the mutex.  */
 133               mutex->__data.__count = 1;
 134               /* But it is inconsistent unless marked otherwise.  */
 135               mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 136
 137               ENQUEUE_MUTEX (mutex);
 138
 139               /* Note that we deliberately exit here.  If we fall
 140                  through to the end of the function __nusers would be
 141                  incremented which is not correct because the old
 142                  owner has to be discounted.  If we are not supposed
 143                  to increment __nusers we actually have to decrement
 144                  it here.  */
 145 #ifdef NO_INCR
 146               --mutex->__data.__nusers;
 147 #endif
 148
 149               return EOWNERDEAD;
 150             }
 151
 152         normal:
 153           /* Check whether we already hold the mutex.  */
 154           if (__builtin_expect ((mutex->__data.__lock & FUTEX_TID_MASK)
 155                                 == id, 0))
 156             {
 157               if (mutex->__data.__kind
 158                   == PTHREAD_MUTEX_ROBUST_PRIVATE_ERRORCHECK_NP)
 159                 return EDEADLK;
 160
 161               if (mutex->__data.__kind
 162                   == PTHREAD_MUTEX_ROBUST_PRIVATE_RECURSIVE_NP)
 163                 {
 164                   /* Just bump the counter.  */
 165                   if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 166                     /* Overflow of the counter.  */
 167                     return EAGAIN;
 168
 169                   ++mutex->__data.__count;
 170
 171                   return 0;
 172                 }
 173             }
 174
 175           oldval = LLL_ROBUST_MUTEX_LOCK (mutex->__data.__lock, id);
 176
 177           if (__builtin_expect (mutex->__data.__owner
 178                                 == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 179             {
 180               /* This mutex is now not recoverable.  */
 181               mutex->__data.__count = 0;
 182               lll_mutex_unlock (mutex->__data.__lock);
 183               return ENOTRECOVERABLE;
 184             }
 185         }
 186       while ((oldval & FUTEX_OWNER_DIED) != 0);
 187
 188       mutex->__data.__count = 1;
 189       ENQUEUE_MUTEX (mutex);
 190       break;
 191
 192     default:
 193       /* Correct code cannot set any other type.  */
 194       return EINVAL;
 195     }
 196
 197   /* Record the ownership.  */
 198   mutex->__data.__owner = id;
 199 #ifndef NO_INCR
 200   ++mutex->__data.__nusers;
 201 #endif
 202
 203   return retval;
 204 }
 205 #ifndef __pthread_mutex_lock
 206 strong_alias (__pthread_mutex_lock, pthread_mutex_lock)
 207 strong_alias (__pthread_mutex_lock, __pthread_mutex_lock_internal)
 208 #endif