nptl/pthread_cond_timedwait.c

   1 /* Copyright (C) 2003-2013 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 #if (defined lll_futex_timed_wait_requeue_pi \
  68      && defined __ASSUME_REQUEUE_PI)
  69   int pi_flag = 0;
  70 #endif
  71
  72   /* Make sure we are alone.  */
  73   lll_lock (cond->__data.__lock, pshared);
  74
  75   /* Now we can release the mutex.  */
  76   int err = __pthread_mutex_unlock_usercnt (mutex, 0);
  77   if (err)
  78     {
  79       lll_unlock (cond->__data.__lock, pshared);
  80       return err;
  81     }
  82
  83   /* We have one new user of the condvar.  */
  84   ++cond->__data.__total_seq;
  85   ++cond->__data.__futex;
  86   cond->__data.__nwaiters += 1 << COND_NWAITERS_SHIFT;
  87
  88   /* Work around the fact that the kernel rejects negative timeout values
  89      despite them being valid.  */
  90   if (__builtin_expect (abstime->tv_sec < 0, 0))
  91     goto timeout;
  92
  93   /* Remember the mutex we are using here.  If there is already a
  94      different address store this is a bad user bug.  Do not store
  95      anything for pshared condvars.  */
  96   if (cond->__data.__mutex != (void *) ~0l)
  97     cond->__data.__mutex = mutex;
  98
  99   /* Prepare structure passed to cancellation handler.  */
 100   cbuffer.cond = cond;
 101   cbuffer.mutex = mutex;
 102
 103   /* Before we block we enable cancellation.  Therefore we have to
 104      install a cancellation handler.  */
 105   __pthread_cleanup_push (&buffer, __condvar_cleanup, &cbuffer);
 106
 107   /* The current values of the wakeup counter.  The "woken" counter
 108      must exceed this value.  */
 109   unsigned long long int val;
 110   unsigned long long int seq;
 111   val = seq = cond->__data.__wakeup_seq;
 112   /* Remember the broadcast counter.  */
 113   cbuffer.bc_seq = cond->__data.__broadcast_seq;
 114
 115   while (1)
 116     {
 117 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
 118      || !defined lll_futex_timed_wait_bitset)
 119       struct timespec rt;
 120       {
 121 # ifdef __NR_clock_gettime
 122         INTERNAL_SYSCALL_DECL (err);
 123         (void) INTERNAL_VSYSCALL (clock_gettime, err, 2,
 124                                   (cond->__data.__nwaiters
 125                                    & ((1 << COND_NWAITERS_SHIFT) - 1)),
 126                                   &rt);
 127         /* Convert the absolute timeout value to a relative timeout.  */
 128         rt.tv_sec = abstime->tv_sec - rt.tv_sec;
 129         rt.tv_nsec = abstime->tv_nsec - rt.tv_nsec;
 130 # else
 131         /* Get the current time.  So far we support only one clock.  */
 132         struct timeval tv;
 133         (void) gettimeofday (&tv, NULL);
 134
 135         /* Convert the absolute timeout value to a relative timeout.  */
 136         rt.tv_sec = abstime->tv_sec - tv.tv_sec;
 137         rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
 138 # endif
 139       }
 140       if (rt.tv_nsec < 0)
 141         {
 142           rt.tv_nsec += 1000000000;
 143           --rt.tv_sec;
 144         }
 145       /* Did we already time out?  */
 146       if (__builtin_expect (rt.tv_sec < 0, 0))
 147         {
 148           if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
 149             goto bc_out;
 150
 151           goto timeout;
 152         }
 153 #endif
 154
 155       unsigned int futex_val = cond->__data.__futex;
 156
 157       /* Prepare to wait.  Release the condvar futex.  */
 158       lll_unlock (cond->__data.__lock, pshared);
 159
 160       /* Enable asynchronous cancellation.  Required by the standard.  */
 161       cbuffer.oldtype = __pthread_enable_asynccancel ();
 162
 163 /* REQUEUE_PI was implemented after FUTEX_CLOCK_REALTIME, so it is sufficient
 164    to check just the former.  */
 165 #if (defined lll_futex_timed_wait_requeue_pi \
 166      && defined __ASSUME_REQUEUE_PI)
 167       /* If pi_flag remained 1 then it means that we had the lock and the mutex
 168          but a spurious waker raced ahead of us.  Give back the mutex before
 169          going into wait again.  */
 170       if (pi_flag)
 171         {
 172           __pthread_mutex_cond_lock_adjust (mutex);
 173           __pthread_mutex_unlock_usercnt (mutex, 0);
 174         }
 175       pi_flag = USE_REQUEUE_PI (mutex);
 176
 177       if (pi_flag)
 178         {
 179           unsigned int clockbit = (cond->__data.__nwaiters & 1
 180                                    ? 0 : FUTEX_CLOCK_REALTIME);
 181           err = lll_futex_timed_wait_requeue_pi (&cond->__data.__futex,
 182                                                  futex_val, abstime, clockbit,
 183                                                  &mutex->__data.__lock,
 184                                                  pshared);
 185           pi_flag = (err == 0);
 186         }
 187       else
 188 #endif
 189
 190         {
 191 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
 192      || !defined lll_futex_timed_wait_bitset)
 193           /* Wait until woken by signal or broadcast.  */
 194           err = lll_futex_timed_wait (&cond->__data.__futex,
 195                                       futex_val, &rt, pshared);
 196 #else
 197           unsigned int clockbit = (cond->__data.__nwaiters & 1
 198                                    ? 0 : FUTEX_CLOCK_REALTIME);
 199           err = lll_futex_timed_wait_bitset (&cond->__data.__futex, futex_val,
 200                                              abstime, clockbit, pshared);
 201 #endif
 202         }
 203
 204       /* Disable asynchronous cancellation.  */
 205       __pthread_disable_asynccancel (cbuffer.oldtype);
 206
 207       /* We are going to look at shared data again, so get the lock.  */
 208       lll_lock (cond->__data.__lock, pshared);
 209
 210       /* If a broadcast happened, we are done.  */
 211       if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
 212         goto bc_out;
 213
 214       /* Check whether we are eligible for wakeup.  */
 215       val = cond->__data.__wakeup_seq;
 216       if (val != seq && cond->__data.__woken_seq != val)
 217         break;
 218
 219       /* Not woken yet.  Maybe the time expired?  */
 220       if (__builtin_expect (err == -ETIMEDOUT, 0))
 221         {
 222         timeout:
 223           /* Yep.  Adjust the counters.  */
 224           ++cond->__data.__wakeup_seq;
 225           ++cond->__data.__futex;
 226
 227           /* The error value.  */
 228           result = ETIMEDOUT;
 229           break;
 230         }
 231     }
 232
 233   /* Another thread woken up.  */
 234   ++cond->__data.__woken_seq;
 235
 236  bc_out:
 237
 238   cond->__data.__nwaiters -= 1 << COND_NWAITERS_SHIFT;
 239
 240   /* If pthread_cond_destroy was called on this variable already,
 241      notify the pthread_cond_destroy caller all waiters have left
 242      and it can be successfully destroyed.  */
 243   if (cond->__data.__total_seq == -1ULL
 244       && cond->__data.__nwaiters < (1 << COND_NWAITERS_SHIFT))
 245     lll_futex_wake (&cond->__data.__nwaiters, 1, pshared);
 246
 247   /* We are done with the condvar.  */
 248   lll_unlock (cond->__data.__lock, pshared);
 249
 250   /* The cancellation handling is back to normal, remove the handler.  */
 251   __pthread_cleanup_pop (&buffer, 0);
 252
 253   /* Get the mutex before returning.  */
 254 #if (defined lll_futex_timed_wait_requeue_pi \
 255      && defined __ASSUME_REQUEUE_PI)
 256   if (pi_flag)
 257     {
 258       __pthread_mutex_cond_lock_adjust (mutex);
 259       err = 0;
 260     }
 261   else
 262 #endif
 263     err = __pthread_mutex_cond_lock (mutex);
 264
 265   return err ?: result;
 266 }
 267
 268 versioned_symbol (libpthread, __pthread_cond_timedwait, pthread_cond_timedwait,
 269                   GLIBC_2_3_2);