nptl/sysdeps/pthread/pthread_cond_timedwait.c

   1 /* Copyright (C) 2003 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
   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 <endian.h>
  21 #include <errno.h>
  22 #include <sysdep.h>
  23 #include <lowlevellock.h>
  24 #include <pthread.h>
  25 #include <pthreadP.h>
  26
  27 #include <shlib-compat.h>
  28
  29
  30 /* Cleanup handler, defined in pthread_cond_wait.c.  */
  31 extern void __condvar_cleanup (void *arg)
  32      __attribute__ ((visibility ("hidden")));
  33
  34 struct _condvar_cleanup_buffer
  35 {
  36   int oldtype;
  37   pthread_cond_t *cond;
  38   pthread_mutex_t *mutex;
  39 };
  40
  41 int
  42 __pthread_cond_timedwait (cond, mutex, abstime)
  43      pthread_cond_t *cond;
  44      pthread_mutex_t *mutex;
  45      const struct timespec *abstime;
  46 {
  47   struct _pthread_cleanup_buffer buffer;
  48   struct _condvar_cleanup_buffer cbuffer;
  49   int result = 0;
  50
  51   /* Catch invalid parameters.  */
  52   if (abstime->tv_nsec >= 1000000000)
  53     return EINVAL;
  54
  55   /* Make sure we are along.  */
  56   lll_mutex_lock (cond->__data.__lock);
  57
  58   /* Now we can release the mutex.  */
  59   int err = __pthread_mutex_unlock_internal (mutex);
  60   if (err)
  61     {
  62       lll_mutex_unlock (cond->__data.__lock);
  63       return err;
  64     }
  65
  66   /* We have one new user of the condvar.  */
  67   ++cond->__data.__total_seq;
  68
  69   /* Prepare structure passed to cancellation handler.  */
  70   cbuffer.cond = cond;
  71   cbuffer.mutex = mutex;
  72
  73   /* Before we block we enable cancellation.  Therefore we have to
  74      install a cancellation handler.  */
  75   __pthread_cleanup_push (&buffer, __condvar_cleanup, &cbuffer);
  76
  77   /* The current values of the wakeup counter.  The "woken" counter
  78      must exceed this value.  */
  79   unsigned long long int val;
  80   unsigned long long int seq;
  81   val = seq = cond->__data.__wakeup_seq;
  82
  83   /* The futex syscall operates on a 32-bit word.  That is fine, we
  84      just use the low 32 bits of the sequence counter.  */
  85 #if BYTE_ORDER == LITTLE_ENDIAN
  86   int *futex = ((int *) (&cond->__data.__wakeup_seq));
  87 #elif BYTE_ORDER == BIG_ENDIAN
  88   int *futex = ((int *) (&cond->__data.__wakeup_seq)) + 1;
  89 #else
  90 # error "No valid byte order"
  91 #endif
  92
  93   while (1)
  94     {
  95       /* Get the current time.  So far we support only one clock.  */
  96       struct timeval tv;
  97       (void) gettimeofday (&tv, NULL);
  98
  99       /* Convert the absolute timeout value to a relative timeout.  */
 100       struct timespec rt;
 101       rt.tv_sec = abstime->tv_sec - tv.tv_sec;
 102       rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
 103       if (rt.tv_nsec < 0)
 104         {
 105           rt.tv_nsec += 1000000000;
 106           --rt.tv_sec;
 107         }
 108       /* Did we already time out?  */
 109       if (rt.tv_sec < 0)
 110         {
 111           /* Yep.  Adjust the sequence counter.  */
 112           ++cond->__data.__wakeup_seq;
 113
 114           /* The error value.  */
 115           result = ETIMEDOUT;
 116           break;
 117         }
 118
 119       /* Prepare to wait.  Release the condvar futex.  */
 120       lll_mutex_unlock (cond->__data.__lock);
 121
 122       /* Enable asynchronous cancellation.  Required by the standard.  */
 123       cbuffer.oldtype = __pthread_enable_asynccancel ();
 124
 125       /* Wait until woken by signal or broadcast.  Note that we
 126          truncate the 'val' value to 32 bits.  */
 127       err = lll_futex_timed_wait (futex, (unsigned int) val, &rt);
 128
 129       /* Disable asynchronous cancellation.  */
 130       __pthread_disable_asynccancel (cbuffer.oldtype);
 131
 132       /* We are going to look at shared data again, so get the lock.  */
 133       lll_mutex_lock(cond->__data.__lock);
 134
 135       /* Check whether we are eligible for wakeup.  */
 136       val = cond->__data.__wakeup_seq;
 137       if (cond->__data.__woken_seq >= seq
 138           && cond->__data.__woken_seq < val)
 139         break;
 140
 141       /* Not woken yet.  Maybe the time expired?  */
 142       if (err == -ETIMEDOUT)
 143         {
 144           /* Yep.  Adjust the counters.  */
 145           ++cond->__data.__wakeup_seq;
 146
 147           /* The error value.  */
 148           result = ETIMEDOUT;
 149           break;
 150         }
 151     }
 152
 153   /* Another thread woken up.  */
 154   ++cond->__data.__woken_seq;
 155
 156   /* We are done with the condvar.  */
 157   lll_mutex_unlock (cond->__data.__lock);
 158
 159   /* The cancellation handling is back to normal, remove the handler.  */
 160   __pthread_cleanup_pop (&buffer, 0);
 161
 162   /* Get the mutex before returning.  */
 163   err = __pthread_mutex_lock_internal (mutex);
 164
 165   return err ?: result;
 166 }
 167
 168 versioned_symbol (libpthread, __pthread_cond_timedwait, pthread_cond_timedwait,
 169                   GLIBC_2_3_2);