nptl/pthread_cond_timedwait.c

   1 /* Copyright (C) 2003-2016 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 <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 (pthread_cond_t *cond, pthread_mutex_t *mutex,
  53                           const struct timespec *abstime)
  54 {
  55   struct _pthread_cleanup_buffer buffer;
  56   struct _condvar_cleanup_buffer cbuffer;
  57   int result = 0;
  58
  59   /* Catch invalid parameters.  */
  60   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
  61     return EINVAL;
  62
  63   int pshared = (cond->__data.__mutex == (void *) ~0l)
  64                 ? LLL_SHARED : LLL_PRIVATE;
  65
  66 #if (defined lll_futex_timed_wait_requeue_pi \
  67      && defined __ASSUME_REQUEUE_PI)
  68   int pi_flag = 0;
  69 #endif
  70
  71   /* Make sure we are alone.  */
  72   lll_lock (cond->__data.__lock, pshared);
  73
  74   /* Now we can release the mutex.  */
  75   int err = __pthread_mutex_unlock_usercnt (mutex, 0);
  76   if (err)
  77     {
  78       lll_unlock (cond->__data.__lock, pshared);
  79       return err;
  80     }
  81
  82   /* We have one new user of the condvar.  */
  83   ++cond->__data.__total_seq;
  84   ++cond->__data.__futex;
  85   cond->__data.__nwaiters += 1 << COND_NWAITERS_SHIFT;
  86
  87   /* Work around the fact that the kernel rejects negative timeout values
  88      despite them being valid.  */
  89   if (__glibc_unlikely (abstime->tv_sec < 0))
  90     goto timeout;
  91
  92   /* Remember the mutex we are using here.  If there is already a
  93      different address store this is a bad user bug.  Do not store
  94      anything for pshared condvars.  */
  95   if (cond->__data.__mutex != (void *) ~0l)
  96     cond->__data.__mutex = mutex;
  97
  98   /* Prepare structure passed to cancellation handler.  */
  99   cbuffer.cond = cond;
 100   cbuffer.mutex = mutex;
 101
 102   /* Before we block we enable cancellation.  Therefore we have to
 103      install a cancellation handler.  */
 104   __pthread_cleanup_push (&buffer, __condvar_cleanup, &cbuffer);
 105
 106   /* The current values of the wakeup counter.  The "woken" counter
 107      must exceed this value.  */
 108   unsigned long long int val;
 109   unsigned long long int seq;
 110   val = seq = cond->__data.__wakeup_seq;
 111   /* Remember the broadcast counter.  */
 112   cbuffer.bc_seq = cond->__data.__broadcast_seq;
 113
 114   while (1)
 115     {
 116 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
 117      || !defined lll_futex_timed_wait_bitset)
 118       struct timespec rt;
 119       {
 120 # ifdef __NR_clock_gettime
 121         INTERNAL_SYSCALL_DECL (err);
 122         (void) INTERNAL_VSYSCALL (clock_gettime, err, 2,
 123                                   (cond->__data.__nwaiters
 124                                    & ((1 << COND_NWAITERS_SHIFT) - 1)),
 125                                   &rt);
 126         /* Convert the absolute timeout value to a relative timeout.  */
 127         rt.tv_sec = abstime->tv_sec - rt.tv_sec;
 128         rt.tv_nsec = abstime->tv_nsec - rt.tv_nsec;
 129 # else
 130         /* Get the current time.  So far we support only one clock.  */
 131         struct timeval tv;
 132         (void) __gettimeofday (&tv, NULL);
 133
 134         /* Convert the absolute timeout value to a relative timeout.  */
 135         rt.tv_sec = abstime->tv_sec - tv.tv_sec;
 136         rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
 137 # endif
 138       }
 139       if (rt.tv_nsec < 0)
 140         {
 141           rt.tv_nsec += 1000000000;
 142           --rt.tv_sec;
 143         }
 144       /* Did we already time out?  */
 145       if (__glibc_unlikely (rt.tv_sec < 0))
 146         {
 147           if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
 148             goto bc_out;
 149
 150           goto timeout;
 151         }
 152 #endif
 153
 154       unsigned int futex_val = cond->__data.__futex;
 155
 156       /* Prepare to wait.  Release the condvar futex.  */
 157       lll_unlock (cond->__data.__lock, pshared);
 158
 159       /* Enable asynchronous cancellation.  Required by the standard.  */
 160       cbuffer.oldtype = __pthread_enable_asynccancel ();
 161
 162 /* REQUEUE_PI was implemented after FUTEX_CLOCK_REALTIME, so it is sufficient
 163    to check just the former.  */
 164 #if (defined lll_futex_timed_wait_requeue_pi \
 165      && defined __ASSUME_REQUEUE_PI)
 166       /* If pi_flag remained 1 then it means that we had the lock and the mutex
 167          but a spurious waker raced ahead of us.  Give back the mutex before
 168          going into wait again.  */
 169       if (pi_flag)
 170         {
 171           __pthread_mutex_cond_lock_adjust (mutex);
 172           __pthread_mutex_unlock_usercnt (mutex, 0);
 173         }
 174       pi_flag = USE_REQUEUE_PI (mutex);
 175
 176       if (pi_flag)
 177         {
 178           unsigned int clockbit = (cond->__data.__nwaiters & 1
 179                                    ? 0 : FUTEX_CLOCK_REALTIME);
 180           err = lll_futex_timed_wait_requeue_pi (&cond->__data.__futex,
 181                                                  futex_val, abstime, clockbit,
 182                                                  &mutex->__data.__lock,
 183                                                  pshared);
 184           pi_flag = (err == 0);
 185         }
 186       else
 187 #endif
 188
 189         {
 190 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
 191      || !defined lll_futex_timed_wait_bitset)
 192           /* Wait until woken by signal or broadcast.  */
 193           err = lll_futex_timed_wait (&cond->__data.__futex,
 194                                       futex_val, &rt, pshared);
 195 #else
 196           unsigned int clockbit = (cond->__data.__nwaiters & 1
 197                                    ? 0 : FUTEX_CLOCK_REALTIME);
 198           err = lll_futex_timed_wait_bitset (&cond->__data.__futex, futex_val,
 199                                              abstime, clockbit, pshared);
 200 #endif
 201         }
 202
 203       /* Disable asynchronous cancellation.  */
 204       __pthread_disable_asynccancel (cbuffer.oldtype);
 205
 206       /* We are going to look at shared data again, so get the lock.  */
 207       lll_lock (cond->__data.__lock, pshared);
 208
 209       /* If a broadcast happened, we are done.  */
 210       if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
 211         goto bc_out;
 212
 213       /* Check whether we are eligible for wakeup.  */
 214       val = cond->__data.__wakeup_seq;
 215       if (val != seq && cond->__data.__woken_seq != val)
 216         break;
 217
 218       /* Not woken yet.  Maybe the time expired?  */
 219       if (__glibc_unlikely (err == -ETIMEDOUT))
 220         {
 221         timeout:
 222           /* Yep.  Adjust the counters.  */
 223           ++cond->__data.__wakeup_seq;
 224           ++cond->__data.__futex;
 225
 226           /* The error value.  */
 227           result = ETIMEDOUT;
 228           break;
 229         }
 230     }
 231
 232   /* Another thread woken up.  */
 233   ++cond->__data.__woken_seq;
 234
 235  bc_out:
 236
 237   cond->__data.__nwaiters -= 1 << COND_NWAITERS_SHIFT;
 238
 239   /* If pthread_cond_destroy was called on this variable already,
 240      notify the pthread_cond_destroy caller all waiters have left
 241      and it can be successfully destroyed.  */
 242   if (cond->__data.__total_seq == -1ULL
 243       && cond->__data.__nwaiters < (1 << COND_NWAITERS_SHIFT))
 244     lll_futex_wake (&cond->__data.__nwaiters, 1, pshared);
 245
 246   /* We are done with the condvar.  */
 247   lll_unlock (cond->__data.__lock, pshared);
 248
 249   /* The cancellation handling is back to normal, remove the handler.  */
 250   __pthread_cleanup_pop (&buffer, 0);
 251
 252   /* Get the mutex before returning.  */
 253 #if (defined lll_futex_timed_wait_requeue_pi \
 254      && defined __ASSUME_REQUEUE_PI)
 255   if (pi_flag)
 256     {
 257       __pthread_mutex_cond_lock_adjust (mutex);
 258       err = 0;
 259     }
 260   else
 261 #endif
 262     err = __pthread_mutex_cond_lock (mutex);
 263
 264   return err ?: result;
 265 }
 266
 267 versioned_symbol (libpthread, __pthread_cond_timedwait, pthread_cond_timedwait,
 268                   GLIBC_2_3_2);