nptl/pthread_cond_timedwait.c

   1 /* Copyright (C) 2003-2014 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 <sys/time.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 #if (defined lll_futex_timed_wait_requeue_pi \
  69      && defined __ASSUME_REQUEUE_PI)
  70   int pi_flag = 0;
  71 #endif
  72
  73   /* Make sure we are alone.  */
  74   lll_lock (cond->__data.__lock, pshared);
  75
  76   /* Now we can release the mutex.  */
  77   int err = __pthread_mutex_unlock_usercnt (mutex, 0);
  78   if (err)
  79     {
  80       lll_unlock (cond->__data.__lock, pshared);
  81       return err;
  82     }
  83
  84   /* We have one new user of the condvar.  */
  85   ++cond->__data.__total_seq;
  86   ++cond->__data.__futex;
  87   cond->__data.__nwaiters += 1 << COND_NWAITERS_SHIFT;
  88
  89   /* Work around the fact that the kernel rejects negative timeout values
  90      despite them being valid.  */
  91   if (__glibc_unlikely (abstime->tv_sec < 0))
  92     goto timeout;
  93
  94   /* Remember the mutex we are using here.  If there is already a
  95      different address store this is a bad user bug.  Do not store
  96      anything for pshared condvars.  */
  97   if (cond->__data.__mutex != (void *) ~0l)
  98     cond->__data.__mutex = mutex;
  99
 100   /* Prepare structure passed to cancellation handler.  */
 101   cbuffer.cond = cond;
 102   cbuffer.mutex = mutex;
 103
 104   /* Before we block we enable cancellation.  Therefore we have to
 105      install a cancellation handler.  */
 106   __pthread_cleanup_push (&buffer, __condvar_cleanup, &cbuffer);
 107
 108   /* The current values of the wakeup counter.  The "woken" counter
 109      must exceed this value.  */
 110   unsigned long long int val;
 111   unsigned long long int seq;
 112   val = seq = cond->__data.__wakeup_seq;
 113   /* Remember the broadcast counter.  */
 114   cbuffer.bc_seq = cond->__data.__broadcast_seq;
 115
 116   while (1)
 117     {
 118 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
 119      || !defined lll_futex_timed_wait_bitset)
 120       struct timespec rt;
 121       {
 122 # ifdef __NR_clock_gettime
 123         INTERNAL_SYSCALL_DECL (err);
 124         (void) INTERNAL_VSYSCALL (clock_gettime, err, 2,
 125                                   (cond->__data.__nwaiters
 126                                    & ((1 << COND_NWAITERS_SHIFT) - 1)),
 127                                   &rt);
 128         /* Convert the absolute timeout value to a relative timeout.  */
 129         rt.tv_sec = abstime->tv_sec - rt.tv_sec;
 130         rt.tv_nsec = abstime->tv_nsec - rt.tv_nsec;
 131 # else
 132         /* Get the current time.  So far we support only one clock.  */
 133         struct timeval tv;
 134         (void) gettimeofday (&tv, NULL);
 135
 136         /* Convert the absolute timeout value to a relative timeout.  */
 137         rt.tv_sec = abstime->tv_sec - tv.tv_sec;
 138         rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
 139 # endif
 140       }
 141       if (rt.tv_nsec < 0)
 142         {
 143           rt.tv_nsec += 1000000000;
 144           --rt.tv_sec;
 145         }
 146       /* Did we already time out?  */
 147       if (__glibc_unlikely (rt.tv_sec < 0))
 148         {
 149           if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
 150             goto bc_out;
 151
 152           goto timeout;
 153         }
 154 #endif
 155
 156       unsigned int futex_val = cond->__data.__futex;
 157
 158       /* Prepare to wait.  Release the condvar futex.  */
 159       lll_unlock (cond->__data.__lock, pshared);
 160
 161       /* Enable asynchronous cancellation.  Required by the standard.  */
 162       cbuffer.oldtype = __pthread_enable_asynccancel ();
 163
 164 /* REQUEUE_PI was implemented after FUTEX_CLOCK_REALTIME, so it is sufficient
 165    to check just the former.  */
 166 #if (defined lll_futex_timed_wait_requeue_pi \
 167      && defined __ASSUME_REQUEUE_PI)
 168       /* If pi_flag remained 1 then it means that we had the lock and the mutex
 169          but a spurious waker raced ahead of us.  Give back the mutex before
 170          going into wait again.  */
 171       if (pi_flag)
 172         {
 173           __pthread_mutex_cond_lock_adjust (mutex);
 174           __pthread_mutex_unlock_usercnt (mutex, 0);
 175         }
 176       pi_flag = USE_REQUEUE_PI (mutex);
 177
 178       if (pi_flag)
 179         {
 180           unsigned int clockbit = (cond->__data.__nwaiters & 1
 181                                    ? 0 : FUTEX_CLOCK_REALTIME);
 182           err = lll_futex_timed_wait_requeue_pi (&cond->__data.__futex,
 183                                                  futex_val, abstime, clockbit,
 184                                                  &mutex->__data.__lock,
 185                                                  pshared);
 186           pi_flag = (err == 0);
 187         }
 188       else
 189 #endif
 190
 191         {
 192 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
 193      || !defined lll_futex_timed_wait_bitset)
 194           /* Wait until woken by signal or broadcast.  */
 195           err = lll_futex_timed_wait (&cond->__data.__futex,
 196                                       futex_val, &rt, pshared);
 197 #else
 198           unsigned int clockbit = (cond->__data.__nwaiters & 1
 199                                    ? 0 : FUTEX_CLOCK_REALTIME);
 200           err = lll_futex_timed_wait_bitset (&cond->__data.__futex, futex_val,
 201                                              abstime, clockbit, pshared);
 202 #endif
 203         }
 204
 205       /* Disable asynchronous cancellation.  */
 206       __pthread_disable_asynccancel (cbuffer.oldtype);
 207
 208       /* We are going to look at shared data again, so get the lock.  */
 209       lll_lock (cond->__data.__lock, pshared);
 210
 211       /* If a broadcast happened, we are done.  */
 212       if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
 213         goto bc_out;
 214
 215       /* Check whether we are eligible for wakeup.  */
 216       val = cond->__data.__wakeup_seq;
 217       if (val != seq && cond->__data.__woken_seq != val)
 218         break;
 219
 220       /* Not woken yet.  Maybe the time expired?  */
 221       if (__glibc_unlikely (err == -ETIMEDOUT))
 222         {
 223         timeout:
 224           /* Yep.  Adjust the counters.  */
 225           ++cond->__data.__wakeup_seq;
 226           ++cond->__data.__futex;
 227
 228           /* The error value.  */
 229           result = ETIMEDOUT;
 230           break;
 231         }
 232     }
 233
 234   /* Another thread woken up.  */
 235   ++cond->__data.__woken_seq;
 236
 237  bc_out:
 238
 239   cond->__data.__nwaiters -= 1 << COND_NWAITERS_SHIFT;
 240
 241   /* If pthread_cond_destroy was called on this variable already,
 242      notify the pthread_cond_destroy caller all waiters have left
 243      and it can be successfully destroyed.  */
 244   if (cond->__data.__total_seq == -1ULL
 245       && cond->__data.__nwaiters < (1 << COND_NWAITERS_SHIFT))
 246     lll_futex_wake (&cond->__data.__nwaiters, 1, pshared);
 247
 248   /* We are done with the condvar.  */
 249   lll_unlock (cond->__data.__lock, pshared);
 250
 251   /* The cancellation handling is back to normal, remove the handler.  */
 252   __pthread_cleanup_pop (&buffer, 0);
 253
 254   /* Get the mutex before returning.  */
 255 #if (defined lll_futex_timed_wait_requeue_pi \
 256      && defined __ASSUME_REQUEUE_PI)
 257   if (pi_flag)
 258     {
 259       __pthread_mutex_cond_lock_adjust (mutex);
 260       err = 0;
 261     }
 262   else
 263 #endif
 264     err = __pthread_mutex_cond_lock (mutex);
 265
 266   return err ?: result;
 267 }
 268
 269 versioned_symbol (libpthread, __pthread_cond_timedwait, pthread_cond_timedwait,
 270                   GLIBC_2_3_2);