pthread_yield_np(3) [osf1 man page]

pthread_yield_np(3)					     Library Functions Manual					       pthread_yield_np(3)

NAME

       pthread_yield_np  -  Notifies  the  scheduler  that  the current thread is willing to release its processor to other threads of the same or
       higher priority.

LIBRARY

       DECthreads POSIX 1003.1c Library (libpthread.so)

SYNOPSIS

       #include <pthread.h>

       int pthread_yield_np(
			 void);

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       IEEE Std 1003.1c-1995, POSIX System Application Program Interface

PARAMETERS

       None

DESCRIPTION

       This routine notifies the thread scheduler that the current thread is willing to release its processor to other threads	of  equivalent	or
       greater	scheduling precedence. (A thread generally will release its processor to a thread of a greater scheduling precedence without call-
       ing this routine.)  If no other threads of equivalent or greater scheduling precedence are ready to execute, the thread continues.

       This routine can allow knowledge of the details of an application to be used to improve	its  performance.   If	a  thread  does  not  call
       pthread_yield_np(3), other threads may be given the opportunity to run at arbitrary points (possibly even when the interrupted thread holds
       a required resource).  By making strategic calls to pthread_yield_np(3), other threads may  be  given  the  opportunity	to  run  when  the
       resources are free.  This improves performance by reducing contention for the resource.

       As  a  general guideline, consider calling this routine after a thread has released a resource (such as a mutex) which is heavily contended
       for by other threads.  This can be especially important if the program is running on a uniprocessor machine, or if the thread acquires  and
       releases the resource inside a tight loop.

       Use  this routine carefully and sparingly, because misuse can cause unnecessary context switching which will increase overhead and actually
       degrade performance.  For example, it is counter-productive for a thread to yield while it holds a resource which the threads to  which	it
       is yielding will need.  Likewise, it is pointless to yield unless there is likely to be another thread which is ready to run.

RETURN VALUES

       If  an  error condition occurs, this routine returns an integer value indicating the type of error.  Possible return values are as follows:
       Successful completion.  The routine is not supported by this implementation.

ERRORS

       None

RELATED INFORMATION

       Functions: pthread_attr_setschedparam(3), pthread_setschedparam(3), pthread_getscheduler(3)

       Manuals: Guide to DECthreads and Programmer's Guide

       delim off

															       pthread_yield_np(3)

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pthread_mutex_unlock(3) 				     Library Functions Manual					   pthread_mutex_unlock(3)

NAME

       pthread_mutex_unlock - Unlocks the specified mutex.

LIBRARY

       DECthreads POSIX 1003.1c Library (libpthread.so)

SYNOPSIS

       #include <pthread.h>

       int   pthread_mutex_unlock(
			      pthread_mutex_t	*mutex);

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       IEEE Std 1003.1c-1995, POSIX System Application Program Interface

PARAMETERS

       Mutex to be unlocked.

DESCRIPTION

       This routine unlocks the mutex specified by the mutex argument.

       This  routine  behaves  as  follows,  based on the type of the specified mutex: For a normal, default, or errorcheck mutex: if the mutex is
       owned by the calling thread, it is unlocked with no current owner.  Further, for a normal or default mutex: if the mutex is not	locked	or
       is locked by another thread, this routine can also return [EPERM], but this is not guaranteed. For an errorcheck mutex: if the mutex is not
       locked or is locked by another thread, this routine returns [EPERM].  For a recursive mutex: if the mutex is owned by the  calling  thread,
       the  lock count is decremented. The mutex remains locked and owned until the lock count reaches zero (0). When the lock count reaches zero,
       the mutex becomes unlocked with no current owner.

       If one or more threads are waiting to lock the specified mutex, and the mutex becomes unlocked, this routine causes one thread  to  unblock
       and  to	try  to  acquire  the mutex.  The scheduling policy is used to determine which thread to unblock.  For the SCHED_FIFO and SCHED_RR
       policies, a blocked thread is chosen in priority order, using first-in/first-out within priorities.  Note  that	the  mutex  might  not	be
       acquired by the awakened thread if any other running thread attempts to lock the mutex first.

       On  Tru64  UNIX,  if a signal is delivered to a thread waiting for a mutex, upon return from the signal handler, the thread resumes waiting
       for the mutex as if it was not interrupted.

RETURN VALUES

       If an error condition occurs, this routine returns an integer value indicating the type of error.  Possible return values are  as  follows:
       Successful completion.  The value specified for mutex is invalid.  The calling thread does not own the mutex.

ERRORS

       None

RELATED INFORMATION

       Functions: pthread_mutexattr_settype(3), pthread_mutex_destroy(3), pthread_mutex_init(3), pthread_mutex_lock(3), pthread_mutex_trylock(3)

       Manuals: Guide to DECthreads and Programmer's Guide

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															   pthread_mutex_unlock(3)

Linux and UNIX Man Pages

pthread_yield_np(3) [osf1 man page]

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