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pthread_lock_global_np(3)


NAME

  pthread_lock_global_np - Locks the DECthreads global mutex


SYNOPSIS

  #include <pthread.h>

  int pthread_lock_global_np(
	  void );


LIBRARY

  DECthreads POSIX 1003.1c Library (libpthread.so)


STANDARDS

  None


PARAMETERS

  None


DESCRIPTION

  This routine locks the DECthreads global mutex. If the global mutex is
  currently held by another thread when a thread calls this routine, the
  calling thread waits for the global mutex to become available and then
  locks it.

  The thread that has locked the global mutex becomes its current owner and
  remains the owner until the same thread has unlocked it. This routine
  returns with the global mutex in the locked state and with the current
  thread as the global mutex's current owner.

  Use the DECthreads global mutex when calling a library package that is not
  designed to run in a multithreaded environment. Unless the documentation
  for a library function specifically states that it is thread safe, assume
  that it is not compatible; in other words, assume it is nonreentrant.

  The global mutex is one lock. Any code that calls any function that is not
  known to be reentrant should use the same lock. This prevents problems
  resulting from dependencies among threads that call library functions and
  those functions' calling other functions, and so on.

  The global mutex is a recursive mutex. A thread that has locked the global
  mutex can relock it without deadlocking. The locking thread must call
  pthread_unlock_global_np(3) as many times as it called this routine, to
  allow another thread to lock the global mutex.


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.


ERRORS

  None


SEE ALSO

  Functions: pthread_unlock_global_np(3)

  Manuals: Guide to DECthreads and Programmer's Guide

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