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pthread_rwlock_wrlock(3)
NAME
  pthread_rwlock_wrlock - Acquires a read-write lock for write access

SYNOPSIS
  #include <pthread.h>

  int pthread_rwlock_wrlock(
	  pthread_rwlock_t *rwlock );

LIBRARY
  DECthreads POSIX 1003.1c Library (libpthread.so)

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

DESCRIPTION
  This routine attempts to acquire a read-write lock for write access. If any
  thread already has acquired the lock for write access or read access, the
  lock is not granted and the calling thread blocks until it can acquire the
  lock. A thread can hold only one lock for write access on a read-write
  lock.

  Results are undefined if the calling thread holds the read-write lock
  (whether for read or write access) at the time this routine is called.

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

  If a thread is interrupted (via a Tru64 UNIX signal or an OpenVMS AST)
  while waiting for a read-write lock for write access, upon return from the
  interrupt routine the thread resumes waiting for the lock as if it had not
  been interrupted.

  Real-time applications can encounter priority inversion when using read-
  write locks. The problem occurs when a high-priority thread acquires a
  read-write lock that is about to be unlocked (that is, posted) by a low-
  priority thread, but the low-priority thread is preempted by a medium-
  priority thread. This scenario leads to priority inversion in that a high-
  priority thread is blocked by lower-priority threads for an unlimited
  period of time. During system design, real-time programmers must take into
  account the possibility of priority inversion and can deal with it in a
  number of ways, such as by having critical sections that are guarded by
  read-write locks execute at a high priority, so that a thread cannot be
  preempted while executing in its critical section.

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.

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

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

ERRORS
  None

SEE ALSO
  Functions: pthread_rwlock_init(3), pthread_rwlockattr_init(3),
  pthread_rwlock_rdlock(3), pthread_rwlock_trywrlock(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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