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glibc  2.9
Functions
pthread_rwlock_timedwrlock.c File Reference
#include <errno.h>
#include <sysdep.h>
#include <lowlevellock.h>
#include <pthread.h>
#include <pthreadP.h>

Go to the source code of this file.

Functions

int pthread_rwlock_timedwrlock (pthread_rwlock_t *rwlock, const struct timespec *abstime)

Function Documentation

int pthread_rwlock_timedwrlock ( pthread_rwlock_t *  rwlock,
const struct timespec abstime 
)

Definition at line 29 of file pthread_rwlock_timedwrlock.c.

{
  int result = 0;

  /* Make sure we are along.  */
  lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);

  while (1)
    {
      int err;

      /* Get the rwlock if there is no writer and no reader.  */
      if (rwlock->__data.__writer == 0 && rwlock->__data.__nr_readers == 0)
       {
         /* Mark self as writer.  */
         rwlock->__data.__writer = THREAD_GETMEM (THREAD_SELF, tid);
         break;
       }

      /* Make sure we are not holding the rwlock as a writer.  This is
        a deadlock situation we recognize and report.  */
      if (__builtin_expect (rwlock->__data.__writer
                         == THREAD_GETMEM (THREAD_SELF, tid), 0))
       {
         result = EDEADLK;
         break;
       }

      /* Make sure the passed in timeout value is valid.  Ideally this
        test would be executed once.  But since it must not be
        performed if we would not block at all simply moving the test
        to the front is no option.  Replicating all the code is
        costly while this test is not.  */
      if (__builtin_expect (abstime->tv_nsec >= 1000000000
                            || abstime->tv_nsec < 0, 0))
       {
         result = EINVAL;
         break;
       }

      /* 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.  */
      struct timespec rt;
      rt.tv_sec = abstime->tv_sec - tv.tv_sec;
      rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
      if (rt.tv_nsec < 0)
       {
         rt.tv_nsec += 1000000000;
         --rt.tv_sec;
       }
      /* Did we already time out?  */
      if (rt.tv_sec < 0)
       {
         result = ETIMEDOUT;
         break;
       }

      /* Remember that we are a writer.  */
      if (++rwlock->__data.__nr_writers_queued == 0)
       {
         /* Overflow on number of queued writers.  */
         --rwlock->__data.__nr_writers_queued;
         result = EAGAIN;
         break;
       }

      int waitval = rwlock->__data.__writer_wakeup;

      /* Free the lock.  */
      lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);

      /* Wait for the writer or reader(s) to finish.  */
      err = lll_futex_timed_wait (&rwlock->__data.__writer_wakeup,
                              waitval, &rt, rwlock->__data.__shared);

      /* Get the lock.  */
      lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);

      /* To start over again, remove the thread from the writer list.  */
      --rwlock->__data.__nr_writers_queued;

      /* Did the futex call time out?  */
      if (err == -ETIMEDOUT)
       {
         result = ETIMEDOUT;
         break;
       }
    }

  /* We are done, free the lock.  */
  lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);

  return result;
}

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