nptl/pthread_mutex_timedlock.c

   1 /* Copyright (C) 2002, 2003, 2004 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 <errno.h>
  21 #include "pthreadP.h"
  22 #include <lowlevellock.h>
  23
  24
  25 int
  26 pthread_mutex_timedlock (mutex, abstime)
  27      pthread_mutex_t *mutex;
  28      const struct timespec *abstime;
  29 {
  30   pid_t id = THREAD_GETMEM (THREAD_SELF, tid);
  31   int result = 0;
  32
  33   /* We must not check ABSTIME here.  If the thread does not block
  34      abstime must not be checked for a valid value.  */
  35
  36   switch (mutex->__data.__kind)
  37     {
  38       /* Recursive mutex.  */
  39     case PTHREAD_MUTEX_RECURSIVE_NP:
  40       /* Check whether we already hold the mutex.  */
  41       if (mutex->__data.__owner == id)
  42         {
  43           /* Just bump the counter.  */
  44           if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
  45             /* Overflow of the counter.  */
  46             return EAGAIN;
  47
  48           ++mutex->__data.__count;
  49
  50           goto out;
  51         }
  52       else
  53         {
  54           /* We have to get the mutex.  */
  55           result = lll_mutex_timedlock (mutex->__data.__lock, abstime);
  56
  57           if (result != 0)
  58             goto out;
  59
  60           /* Only locked once so far.  */
  61           mutex->__data.__count = 1;
  62         }
  63       break;
  64
  65       /* Error checking mutex.  */
  66     case PTHREAD_MUTEX_ERRORCHECK_NP:
  67       /* Check whether we already hold the mutex.  */
  68       if (mutex->__data.__owner == id)
  69         return EDEADLK;
  70
  71       /* FALLTHROUGH */
  72
  73     default:
  74       /* Correct code cannot set any other type.  */
  75     case PTHREAD_MUTEX_TIMED_NP:
  76     simple:
  77       /* Normal mutex.  */
  78       result = lll_mutex_timedlock (mutex->__data.__lock, abstime);
  79       break;
  80
  81     case PTHREAD_MUTEX_ADAPTIVE_NP:
  82       if (! __is_smp)
  83         goto simple;
  84
  85       if (lll_mutex_trylock (mutex->__data.__lock) != 0)
  86         {
  87           int cnt = 0;
  88           int max_cnt = MIN (MAX_ADAPTIVE_COUNT,
  89                              mutex->__data.__spins * 2 + 10);
  90           do
  91             {
  92               if (cnt++ >= max_cnt)
  93                 {
  94                   result = lll_mutex_timedlock (mutex->__data.__lock, abstime);
  95                   break;
  96                 }
  97
  98 #ifdef BUSY_WAIT_NOP
  99               BUSY_WAIT_NOP;
 100 #endif
 101             }
 102           while (lll_mutex_trylock (mutex->__data.__lock) != 0);
 103
 104           mutex->__data.__spins += (cnt - mutex->__data.__spins) / 8;
 105         }
 106       break;
 107     }
 108
 109   if (result == 0)
 110     {
 111       /* Record the ownership.  */
 112       mutex->__data.__owner = id;
 113       ++mutex->__data.__nusers;
 114     }
 115
 116  out:
 117   return result;
 118 }