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   /* Work around the fact that the kernel rejects negative timeout values
  84      despite them being valid.  */
  85   if (__builtin_expect (abstime->tv_sec < 0, 0))
  86     goto timeout;
  87
  88   /* Remember the mutex we are using here.  If there is already a
  89      different address store this is a bad user bug.  Do not store
  90      anything for pshared condvars.  */
  91   if (cond->__data.__mutex != (void *) ~0l)
  92     cond->__data.__mutex = mutex;
  93
  94   /* Prepare structure passed to cancellation handler.  */
  95   cbuffer.cond = cond;
  96   cbuffer.mutex = mutex;
  97
  98   /* Before we block we enable cancellation.  Therefore we have to
  99      install a cancellation handler.  */
 100   __pthread_cleanup_push (&buffer, __condvar_cleanup, &cbuffer);
 101
 102   /* The current values of the wakeup counter.  The "woken" counter
 103      must exceed this value.  */
 104   unsigned long long int val;
 105   unsigned long long int seq;
 106   val = seq = cond->__data.__wakeup_seq;
 107   /* Remember the broadcast counter.  */
 108   cbuffer.bc_seq = cond->__data.__broadcast_seq;
 109
 110   while (1)
 111     {
 112 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
 113      || !defined lll_futex_timed_wait_bitset)
 114       struct timespec rt;
 115       {
 116 # ifdef __NR_clock_gettime
 117         INTERNAL_SYSCALL_DECL (err);
 118         (void) INTERNAL_VSYSCALL (clock_gettime, err, 2,
 119                                   (cond->__data.__nwaiters
 120                                    & ((1 << COND_NWAITERS_SHIFT) - 1)),
 121                                   &rt);
 122         /* Convert the absolute timeout value to a relative timeout.  */
 123         rt.tv_sec = abstime->tv_sec - rt.tv_sec;
 124         rt.tv_nsec = abstime->tv_nsec - rt.tv_nsec;
 125 # else
 126         /* Get the current time.  So far we support only one clock.  */
 127         struct timeval tv;
 128         (void) gettimeofday (&tv, NULL);
 129
 130         /* Convert the absolute timeout value to a relative timeout.  */
 131         rt.tv_sec = abstime->tv_sec - tv.tv_sec;
 132         rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
 133 # endif
 134       }
 135       if (rt.tv_nsec < 0)
 136         {
 137           rt.tv_nsec += 1000000000;
 138           --rt.tv_sec;
 139         }
 140       /* Did we already time out?  */
 141       if (__builtin_expect (rt.tv_sec < 0, 0))
 142         {
 143           if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
 144             goto bc_out;
 145
 146           goto timeout;
 147         }
 148 #endif
 149
 150       unsigned int futex_val = cond->__data.__futex;
 151
 152       /* Prepare to wait.  Release the condvar futex.  */
 153       lll_unlock (cond->__data.__lock, pshared);
 154
 155       /* Enable asynchronous cancellation.  Required by the standard.  */
 156       cbuffer.oldtype = __pthread_enable_asynccancel ();
 157
 158 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
 159      || !defined lll_futex_timed_wait_bitset)
 160       /* Wait until woken by signal or broadcast.  */
 161       err = lll_futex_timed_wait (&cond->__data.__futex,
 162                                   futex_val, &rt, pshared);
 163 #else
 164       unsigned int clockbit = (cond->__data.__nwaiters & 1
 165                                ? 0 : FUTEX_CLOCK_REALTIME);
 166       err = lll_futex_timed_wait_bitset (&cond->__data.__futex, futex_val,
 167                                          abstime, clockbit, pshared);
 168 #endif
 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);