nptl/pthread_cond_timedwait.c

   1 /* Copyright (C) 2003, 2004, 2007, 2010 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 #include <kernel-features.h>
  27
  28 #include <shlib-compat.h>
  29
  30 #ifndef HAVE_CLOCK_GETTIME_VSYSCALL
  31 # undef INTERNAL_VSYSCALL
  32 # define INTERNAL_VSYSCALL INTERNAL_SYSCALL
  33 # undef INLINE_VSYSCALL
  34 # define INLINE_VSYSCALL INLINE_SYSCALL
  35 #else
  36 # include <bits/libc-vdso.h>
  37 #endif
  38
  39 /* Cleanup handler, defined in pthread_cond_wait.c.  */
  40 extern void __condvar_cleanup (void *arg)
  41      __attribute__ ((visibility ("hidden")));
  42
  43 struct _condvar_cleanup_buffer
  44 {
  45   int oldtype;
  46   pthread_cond_t *cond;
  47   pthread_mutex_t *mutex;
  48   unsigned int bc_seq;
  49 };
  50
  51 int
  52 __pthread_cond_timedwait (cond, mutex, abstime)
  53      pthread_cond_t *cond;
  54      pthread_mutex_t *mutex;
  55      const struct timespec *abstime;
  56 {
  57   struct _pthread_cleanup_buffer buffer;
  58   struct _condvar_cleanup_buffer cbuffer;
  59   int result = 0;
  60
  61   /* Catch invalid parameters.  */
  62   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
  63     return EINVAL;
  64
  65   int pshared = (cond->__data.__mutex == (void *) ~0l)
  66                 ? LLL_SHARED : LLL_PRIVATE;
  67
  68   /* Make sure we are along.  */
  69   lll_lock (cond->__data.__lock, pshared);
  70
  71   /* Now we can release the mutex.  */
  72   int err = __pthread_mutex_unlock_usercnt (mutex, 0);
  73   if (err)
  74     {
  75       lll_unlock (cond->__data.__lock, pshared);
  76       return err;
  77     }
  78
  79   /* We have one new user of the condvar.  */
  80   ++cond->__data.__total_seq;
  81   ++cond->__data.__futex;
  82   cond->__data.__nwaiters += 1 << COND_NWAITERS_SHIFT;
  83
  84   /* Remember the mutex we are using here.  If there is already a
  85      different address store this is a bad user bug.  Do not store
  86      anything for pshared condvars.  */
  87   if (cond->__data.__mutex != (void *) ~0l)
  88     cond->__data.__mutex = mutex;
  89
  90   /* Prepare structure passed to cancellation handler.  */
  91   cbuffer.cond = cond;
  92   cbuffer.mutex = mutex;
  93
  94   /* Before we block we enable cancellation.  Therefore we have to
  95      install a cancellation handler.  */
  96   __pthread_cleanup_push (&buffer, __condvar_cleanup, &cbuffer);
  97
  98   /* The current values of the wakeup counter.  The "woken" counter
  99      must exceed this value.  */
 100   unsigned long long int val;
 101   unsigned long long int seq;
 102   val = seq = cond->__data.__wakeup_seq;
 103   /* Remember the broadcast counter.  */
 104   cbuffer.bc_seq = cond->__data.__broadcast_seq;
 105
 106   while (1)
 107     {
 108       struct timespec rt;
 109       {
 110 #ifdef __NR_clock_gettime
 111         INTERNAL_SYSCALL_DECL (err);
 112         int ret;
 113         ret = INTERNAL_VSYSCALL (clock_gettime, err, 2,
 114                                 (cond->__data.__nwaiters
 115                                  & ((1 << COND_NWAITERS_SHIFT) - 1)),
 116                                 &rt);
 117 # ifndef __ASSUME_POSIX_TIMERS
 118         if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (ret, err), 0))
 119           {
 120             struct timeval tv;
 121             (void) gettimeofday (&tv, NULL);
 122
 123             /* Convert the absolute timeout value to a relative timeout.  */
 124             rt.tv_sec = abstime->tv_sec - tv.tv_sec;
 125             rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
 126           }
 127         else
 128 # endif
 129           {
 130             /* Convert the absolute timeout value to a relative timeout.  */
 131             rt.tv_sec = abstime->tv_sec - rt.tv_sec;
 132             rt.tv_nsec = abstime->tv_nsec - rt.tv_nsec;
 133           }
 134 #else
 135         /* Get the current time.  So far we support only one clock.  */
 136         struct timeval tv;
 137         (void) gettimeofday (&tv, NULL);
 138
 139         /* Convert the absolute timeout value to a relative timeout.  */
 140         rt.tv_sec = abstime->tv_sec - tv.tv_sec;
 141         rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
 142 #endif
 143       }
 144       if (rt.tv_nsec < 0)
 145         {
 146           rt.tv_nsec += 1000000000;
 147           --rt.tv_sec;
 148         }
 149       /* Did we already time out?  */
 150       if (__builtin_expect (rt.tv_sec < 0, 0))
 151         {
 152           if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
 153             goto bc_out;
 154
 155           goto timeout;
 156         }
 157
 158       unsigned int futex_val = cond->__data.__futex;
 159
 160       /* Prepare to wait.  Release the condvar futex.  */
 161       lll_unlock (cond->__data.__lock, pshared);
 162
 163       /* Enable asynchronous cancellation.  Required by the standard.  */
 164       cbuffer.oldtype = __pthread_enable_asynccancel ();
 165
 166       /* Wait until woken by signal or broadcast.  */
 167       err = lll_futex_timed_wait (&cond->__data.__futex,
 168                                   futex_val, &rt, pshared);
 169
 170       /* Disable asynchronous cancellation.  */
 171       __pthread_disable_asynccancel (cbuffer.oldtype);
 172
 173       /* We are going to look at shared data again, so get the lock.  */
 174       lll_lock (cond->__data.__lock, pshared);
 175
 176       /* If a broadcast happened, we are done.  */
 177       if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
 178         goto bc_out;
 179
 180       /* Check whether we are eligible for wakeup.  */
 181       val = cond->__data.__wakeup_seq;
 182       if (val != seq && cond->__data.__woken_seq != val)
 183         break;
 184
 185       /* Not woken yet.  Maybe the time expired?  */
 186       if (__builtin_expect (err == -ETIMEDOUT, 0))
 187         {
 188         timeout:
 189           /* Yep.  Adjust the counters.  */
 190           ++cond->__data.__wakeup_seq;
 191           ++cond->__data.__futex;
 192
 193           /* The error value.  */
 194           result = ETIMEDOUT;
 195           break;
 196         }
 197     }
 198
 199   /* Another thread woken up.  */
 200   ++cond->__data.__woken_seq;
 201
 202  bc_out:
 203
 204   cond->__data.__nwaiters -= 1 << COND_NWAITERS_SHIFT;
 205
 206   /* If pthread_cond_destroy was called on this variable already,
 207      notify the pthread_cond_destroy caller all waiters have left
 208      and it can be successfully destroyed.  */
 209   if (cond->__data.__total_seq == -1ULL
 210       && cond->__data.__nwaiters < (1 << COND_NWAITERS_SHIFT))
 211     lll_futex_wake (&cond->__data.__nwaiters, 1, pshared);
 212
 213   /* We are done with the condvar.  */
 214   lll_unlock (cond->__data.__lock, pshared);
 215
 216   /* The cancellation handling is back to normal, remove the handler.  */
 217   __pthread_cleanup_pop (&buffer, 0);
 218
 219   /* Get the mutex before returning.  */
 220   err = __pthread_mutex_cond_lock (mutex);
 221
 222   return err ?: result;
 223 }
 224
 225 versioned_symbol (libpthread, __pthread_cond_timedwait, pthread_cond_timedwait,
 226                   GLIBC_2_3_2);