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pthread_rwlock_tryrdlock(3)
NAME
  pthread_rwlock_tryrdlock - Attempts to acquire a read-write lock for read
  access without waiting

SYNOPSIS
  #include <pthread.h>

  int pthread_rwlock_tryrdlock(
	  pthread_rwlock_t *rwlock );

LIBRARY
  DECthreads POSIX 1003.1c Library (libpthread.so)

PARAMETERS
  rwlock
      Address of the read-write lock object to acquire for read access.

DESCRIPTION
  This routine attempts to acquire a read-write lock for read access, but
  does not wait for the lock if it not immediately available.

  If a thread already holds the lock for read access, the lock is granted and
  this routine returns. If no thread already holds the lock for write access
  and there are no writers waiting to acquire the lock, the lock for read
  access is granted to the calling thread and this routine returns.

  If some thread already holds the lock for write access, the calling thread
  will not acquire the read lock. Results are undefined if the calling thread
  has already acquired a lock for write access on rwlock when this routine is
  called.

  A thread can hold multiple, concurrent locks for read access on the same
  read-write lock. In a given thread, for each call to this routine that
  successfully acquires the same read-write lock for read access, a
  corresponding call to pthread_rwlock_unlock must be issued.

  If the read-write lock object referenced by rwlock is not initialized, the
  results of calling this routine are undefined.

RETURN VALUES
  If an error condition occurs, this routine returns an integer value
  indicating the type of error. Possible return values are as follows:

  0   Successful completion.

  [EBUSY]
      The read-write lock could not be acquired for read access because
      another thread already acquired it for write access or is blocked and
      waiting for it for write access.

  [EINVAL]
      The value specified by rwlock does not refer to an initialized read-
      write lock object.

  [EDEADLCK]
      The current thread already owns the read-write lock for writing.

  [EAGAIN]
      The lock for read access could not be acquired because the maximum
      number of read lock acquisitions for rwlock has been exceeded.

ERRORS
  None

SEE ALSO
  Functions: pthread_rwlock_init(3), pthread_rwlockattr_init(3),
  pthread_rwlock_rdlock(3), pthread_rwlock_wrlock(3),
  pthread_rwlock_unlock(3)

  Manuals: Guide to DECthreads and Programmer's Guide

Index for Section 3

Alphabetical listing for P

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