nptl/pthread_cond_timedwait.c

   1 /* Copyright (C) 2003-2012 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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <endian.h>
  20 #include <errno.h>
  21 #include <sysdep.h>
  22 #include <lowlevellock.h>
  23 #include <pthread.h>
  24 #include <pthreadP.h>
  25 #include <kernel-features.h>
  26
  27 #include <shlib-compat.h>
  28
  29 #ifndef HAVE_CLOCK_GETTIME_VSYSCALL
  30 # undef INTERNAL_VSYSCALL
  31 # define INTERNAL_VSYSCALL INTERNAL_SYSCALL
  32 # undef INLINE_VSYSCALL
  33 # define INLINE_VSYSCALL INLINE_SYSCALL
  34 #else
  35 # include <bits/libc-vdso.h>
  36 #endif
  37
  38 /* Cleanup handler, defined in pthread_cond_wait.c.  */
  39 extern void __condvar_cleanup (void *arg)
  40      __attribute__ ((visibility ("hidden")));
  41
  42 struct _condvar_cleanup_buffer
  43 {
  44   int oldtype;
  45   pthread_cond_t *cond;
  46   pthread_mutex_t *mutex;
  47   unsigned int bc_seq;
  48 };
  49
  50 int
  51 __pthread_cond_timedwait (cond, mutex, abstime)
  52      pthread_cond_t *cond;
  53      pthread_mutex_t *mutex;
  54      const struct timespec *abstime;
  55 {
  56   struct _pthread_cleanup_buffer buffer;
  57   struct _condvar_cleanup_buffer cbuffer;
  58   int result = 0;
  59
  60   /* Catch invalid parameters.  */
  61   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
  62     return EINVAL;
  63
  64   int pshared = (cond->__data.__mutex == (void *) ~0l)
  65                 ? LLL_SHARED : LLL_PRIVATE;
  66
  67   /* Make sure we are alone.  */
  68   lll_lock (cond->__data.__lock, pshared);
  69
  70   /* Now we can release the mutex.  */
  71   int err = __pthread_mutex_unlock_usercnt (mutex, 0);
  72   if (err)
  73     {
  74       lll_unlock (cond->__data.__lock, pshared);
  75       return err;
  76     }
  77
  78   /* We have one new user of the condvar.  */
  79   ++cond->__data.__total_seq;
  80   ++cond->__data.__futex;
  81   cond->__data.__nwaiters += 1 << COND_NWAITERS_SHIFT;
  82
  83   /* Remember the mutex we are using here.  If there is already a
  84      different address store this is a bad user bug.  Do not store
  85      anything for pshared condvars.  */
  86   if (cond->__data.__mutex != (void *) ~0l)
  87     cond->__data.__mutex = mutex;
  88
  89   /* Prepare structure passed to cancellation handler.  */
  90   cbuffer.cond = cond;
  91   cbuffer.mutex = mutex;
  92
  93   /* Before we block we enable cancellation.  Therefore we have to
  94      install a cancellation handler.  */
  95   __pthread_cleanup_push (&buffer, __condvar_cleanup, &cbuffer);
  96
  97   /* The current values of the wakeup counter.  The "woken" counter
  98      must exceed this value.  */
  99   unsigned long long int val;
 100   unsigned long long int seq;
 101   val = seq = cond->__data.__wakeup_seq;
 102   /* Remember the broadcast counter.  */
 103   cbuffer.bc_seq = cond->__data.__broadcast_seq;
 104
 105   while (1)
 106     {
 107       struct timespec rt;
 108       {
 109 #ifdef __NR_clock_gettime
 110         INTERNAL_SYSCALL_DECL (err);
 111         int ret;
 112         ret = INTERNAL_VSYSCALL (clock_gettime, err, 2,
 113                                 (cond->__data.__nwaiters
 114                                  & ((1 << COND_NWAITERS_SHIFT) - 1)),
 115                                 &rt);
 116         /* Convert the absolute timeout value to a relative timeout.  */
 117         rt.tv_sec = abstime->tv_sec - rt.tv_sec;
 118         rt.tv_nsec = abstime->tv_nsec - rt.tv_nsec;
 119 #else
 120         /* Get the current time.  So far we support only one clock.  */
 121         struct timeval tv;
 122         (void) gettimeofday (&tv, NULL);
 123
 124         /* Convert the absolute timeout value to a relative timeout.  */
 125         rt.tv_sec = abstime->tv_sec - tv.tv_sec;
 126         rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
 127 #endif
 128       }
 129       if (rt.tv_nsec < 0)
 130         {
 131           rt.tv_nsec += 1000000000;
 132           --rt.tv_sec;
 133         }
 134       /* Did we already time out?  */
 135       if (__builtin_expect (rt.tv_sec < 0, 0))
 136         {
 137           if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
 138             goto bc_out;
 139
 140           goto timeout;
 141         }
 142
 143       unsigned int futex_val = cond->__data.__futex;
 144
 145       /* Prepare to wait.  Release the condvar futex.  */
 146       lll_unlock (cond->__data.__lock, pshared);
 147
 148       /* Enable asynchronous cancellation.  Required by the standard.  */
 149       cbuffer.oldtype = __pthread_enable_asynccancel ();
 150
 151       /* Wait until woken by signal or broadcast.  */
 152       err = lll_futex_timed_wait (&cond->__data.__futex,
 153                                   futex_val, &rt, pshared);
 154
 155       /* Disable asynchronous cancellation.  */
 156       __pthread_disable_asynccancel (cbuffer.oldtype);
 157
 158       /* We are going to look at shared data again, so get the lock.  */
 159       lll_lock (cond->__data.__lock, pshared);
 160
 161       /* If a broadcast happened, we are done.  */
 162       if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
 163         goto bc_out;
 164
 165       /* Check whether we are eligible for wakeup.  */
 166       val = cond->__data.__wakeup_seq;
 167       if (val != seq && cond->__data.__woken_seq != val)
 168         break;
 169
 170       /* Not woken yet.  Maybe the time expired?  */
 171       if (__builtin_expect (err == -ETIMEDOUT, 0))
 172         {
 173         timeout:
 174           /* Yep.  Adjust the counters.  */
 175           ++cond->__data.__wakeup_seq;
 176           ++cond->__data.__futex;
 177
 178           /* The error value.  */
 179           result = ETIMEDOUT;
 180           break;
 181         }
 182     }
 183
 184   /* Another thread woken up.  */
 185   ++cond->__data.__woken_seq;
 186
 187  bc_out:
 188
 189   cond->__data.__nwaiters -= 1 << COND_NWAITERS_SHIFT;
 190
 191   /* If pthread_cond_destroy was called on this variable already,
 192      notify the pthread_cond_destroy caller all waiters have left
 193      and it can be successfully destroyed.  */
 194   if (cond->__data.__total_seq == -1ULL
 195       && cond->__data.__nwaiters < (1 << COND_NWAITERS_SHIFT))
 196     lll_futex_wake (&cond->__data.__nwaiters, 1, pshared);
 197
 198   /* We are done with the condvar.  */
 199   lll_unlock (cond->__data.__lock, pshared);
 200
 201   /* The cancellation handling is back to normal, remove the handler.  */
 202   __pthread_cleanup_pop (&buffer, 0);
 203
 204   /* Get the mutex before returning.  */
 205   err = __pthread_mutex_cond_lock (mutex);
 206
 207   return err ?: result;
 208 }
 209
 210 versioned_symbol (libpthread, __pthread_cond_timedwait, pthread_cond_timedwait,
 211                   GLIBC_2_3_2);