pthread_cond_timedwait.c

/* Copyright (C) 2003-2016 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include <endian.h>
#include <errno.h>
#include <sysdep.h>
#include <lowlevellock.h>
#include <pthread.h>
#include <pthreadP.h>
#include <sys/time.h>
#include <kernel-features.h>

#include <shlib-compat.h>

#ifndef HAVE_CLOCK_GETTIME_VSYSCALL
# undef INTERNAL_VSYSCALL
# define INTERNAL_VSYSCALL INTERNAL_SYSCALL
# undef INLINE_VSYSCALL
# define INLINE_VSYSCALL INLINE_SYSCALL
#else
# include <libc-vdso.h>
#endif

/* Cleanup handler, defined in pthread_cond_wait.c.  */
extern void __condvar_cleanup (void *arg)
     __attribute__ ((visibility ("hidden")));

struct _condvar_cleanup_buffer
{
  int oldtype;
  pthread_cond_t *cond;
  pthread_mutex_t *mutex;
  unsigned int bc_seq;
};

int
__pthread_cond_timedwait (pthread_cond_t *cond, pthread_mutex_t *mutex,
			  const struct timespec *abstime)
{
  struct _pthread_cleanup_buffer buffer;
  struct _condvar_cleanup_buffer cbuffer;
  int result = 0;

  /* Catch invalid parameters.  */
  if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
    return EINVAL;

  int pshared = (cond->__data.__mutex == (void *) ~0l)
		? LLL_SHARED : LLL_PRIVATE;

#if (defined lll_futex_timed_wait_requeue_pi \
     && defined __ASSUME_REQUEUE_PI)
  int pi_flag = 0;
#endif

  /* Make sure we are alone.  */
  lll_lock (cond->__data.__lock, pshared);

  /* Now we can release the mutex.  */
  int err = __pthread_mutex_unlock_usercnt (mutex, 0);
  if (err)
    {
      lll_unlock (cond->__data.__lock, pshared);
      return err;
    }

  /* We have one new user of the condvar.  */
  ++cond->__data.__total_seq;
  ++cond->__data.__futex;
  cond->__data.__nwaiters += 1 << COND_NWAITERS_SHIFT;

  /* Work around the fact that the kernel rejects negative timeout values
     despite them being valid.  */
  if (__glibc_unlikely (abstime->tv_sec < 0))
    goto timeout;

  /* Remember the mutex we are using here.  If there is already a
     different address store this is a bad user bug.  Do not store
     anything for pshared condvars.  */
  if (cond->__data.__mutex != (void *) ~0l)
    cond->__data.__mutex = mutex;

  /* Prepare structure passed to cancellation handler.  */
  cbuffer.cond = cond;
  cbuffer.mutex = mutex;

  /* Before we block we enable cancellation.  Therefore we have to
     install a cancellation handler.  */
  __pthread_cleanup_push (&buffer, __condvar_cleanup, &cbuffer);

  /* The current values of the wakeup counter.  The "woken" counter
     must exceed this value.  */
  unsigned long long int val;
  unsigned long long int seq;
  val = seq = cond->__data.__wakeup_seq;
  /* Remember the broadcast counter.  */
  cbuffer.bc_seq = cond->__data.__broadcast_seq;

  while (1)
    {
#if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
     || !defined lll_futex_timed_wait_bitset)
      struct timespec rt;
      {
# ifdef __NR_clock_gettime
	INTERNAL_SYSCALL_DECL (err);
	(void) INTERNAL_VSYSCALL (clock_gettime, err, 2,
				  (cond->__data.__nwaiters
				   & ((1 << COND_NWAITERS_SHIFT) - 1)),
				  &rt);
	/* Convert the absolute timeout value to a relative timeout.  */
	rt.tv_sec = abstime->tv_sec - rt.tv_sec;
	rt.tv_nsec = abstime->tv_nsec - rt.tv_nsec;
# else
	/* Get the current time.  So far we support only one clock.  */
	struct timeval tv;
	(void) __gettimeofday (&tv, NULL);

	/* Convert the absolute timeout value to a relative timeout.  */
	rt.tv_sec = abstime->tv_sec - tv.tv_sec;
	rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
# endif
      }
      if (rt.tv_nsec < 0)
	{
	  rt.tv_nsec += 1000000000;
	  --rt.tv_sec;
	}
      /* Did we already time out?  */
      if (__glibc_unlikely (rt.tv_sec < 0))
	{
	  if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
	    goto bc_out;

	  goto timeout;
	}
#endif

      unsigned int futex_val = cond->__data.__futex;

      /* Prepare to wait.  Release the condvar futex.  */
      lll_unlock (cond->__data.__lock, pshared);

      /* Enable asynchronous cancellation.  Required by the standard.  */
      cbuffer.oldtype = __pthread_enable_asynccancel ();

/* REQUEUE_PI was implemented after FUTEX_CLOCK_REALTIME, so it is sufficient
   to check just the former.  */
#if (defined lll_futex_timed_wait_requeue_pi \
     && defined __ASSUME_REQUEUE_PI)
      /* If pi_flag remained 1 then it means that we had the lock and the mutex
	 but a spurious waker raced ahead of us.  Give back the mutex before
	 going into wait again.  */
      if (pi_flag)
	{
	  __pthread_mutex_cond_lock_adjust (mutex);
	  __pthread_mutex_unlock_usercnt (mutex, 0);
	}
      pi_flag = USE_REQUEUE_PI (mutex);

      if (pi_flag)
	{
	  unsigned int clockbit = (cond->__data.__nwaiters & 1
				   ? 0 : FUTEX_CLOCK_REALTIME);
	  err = lll_futex_timed_wait_requeue_pi (&cond->__data.__futex,
						 futex_val, abstime, clockbit,
						 &mutex->__data.__lock,
						 pshared);
	  pi_flag = (err == 0);
	}
      else
#endif

	{
#if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
     || !defined lll_futex_timed_wait_bitset)
	  /* Wait until woken by signal or broadcast.  */
	  err = lll_futex_timed_wait (&cond->__data.__futex,
				      futex_val, &rt, pshared);
#else
	  unsigned int clockbit = (cond->__data.__nwaiters & 1
				   ? 0 : FUTEX_CLOCK_REALTIME);
	  err = lll_futex_timed_wait_bitset (&cond->__data.__futex, futex_val,
					     abstime, clockbit, pshared);
#endif
	}

      /* Disable asynchronous cancellation.  */
      __pthread_disable_asynccancel (cbuffer.oldtype);

      /* We are going to look at shared data again, so get the lock.  */
      lll_lock (cond->__data.__lock, pshared);

      /* If a broadcast happened, we are done.  */
      if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
	goto bc_out;

      /* Check whether we are eligible for wakeup.  */
      val = cond->__data.__wakeup_seq;
      if (val != seq && cond->__data.__woken_seq != val)
	break;

      /* Not woken yet.  Maybe the time expired?  */
      if (__glibc_unlikely (err == -ETIMEDOUT))
	{
	timeout:
	  /* Yep.  Adjust the counters.  */
	  ++cond->__data.__wakeup_seq;
	  ++cond->__data.__futex;

	  /* The error value.  */
	  result = ETIMEDOUT;
	  break;
	}
    }

  /* Another thread woken up.  */
  ++cond->__data.__woken_seq;

 bc_out:

  cond->__data.__nwaiters -= 1 << COND_NWAITERS_SHIFT;

  /* If pthread_cond_destroy was called on this variable already,
     notify the pthread_cond_destroy caller all waiters have left
     and it can be successfully destroyed.  */
  if (cond->__data.__total_seq == -1ULL
      && cond->__data.__nwaiters < (1 << COND_NWAITERS_SHIFT))
    lll_futex_wake (&cond->__data.__nwaiters, 1, pshared);

  /* We are done with the condvar.  */
  lll_unlock (cond->__data.__lock, pshared);

  /* The cancellation handling is back to normal, remove the handler.  */
  __pthread_cleanup_pop (&buffer, 0);

  /* Get the mutex before returning.  */
#if (defined lll_futex_timed_wait_requeue_pi \
     && defined __ASSUME_REQUEUE_PI)
  if (pi_flag)
    {
      __pthread_mutex_cond_lock_adjust (mutex);
      err = 0;
    }
  else
#endif
    err = __pthread_mutex_cond_lock (mutex);

  return err ?: result;
}

versioned_symbol (libpthread, __pthread_cond_timedwait, pthread_cond_timedwait,
		  GLIBC_2_3_2);