osf1 man page for pthread_cond_sig_preempt_int_np

pthread_cond_sig_preempt_int_np(3)			     Library Functions Manual				pthread_cond_sig_preempt_int_np(3)

NAME
       pthread_cond_sig_preempt_int_np - Wakes one thread that is waiting on the specified condition variable (called from interrupt level only).

LIBRARY
       DECthreads POSIX 1003.1c Library (libpthread.so)

SYNOPSIS
       #include <pthread.h>

       int pthread_cond_sig_preempt_int_np(
			 pthread_cond_t    *cond);

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

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

PARAMETERS
       Condition variable to be signaled.

DESCRIPTION
       This  routine  wakes one thread waiting on a condition variable.  It can only be called from a software interrupt handler routine.  Calling
       this routine implies that it might be possible for a single waiting thread to proceed.  Call this routine when any thread  waiting  on  the
       specified condition variable might find its predicate true.

       The  scheduling policies of the waiting threads determine which thread is awakened.  For policies SCHED_FIFO and SCHED_RR, a blocked thread
       is chosen in priority order, using first-in/first-out (FIFO) within priorities.

       You can call this routine when the associated mutex is either locked or unlocked.  Never try to lock a mutex from an interrupt handler.

       This routine allows you to signal a thread from a software interrupt handler.  Do not call this routine from  noninterrupt  code.   If  you
       want to signal a thread from the normal interrupt level, use pthread_cond_signal(3).

       NOTE:  If  a  waiting  thread has a preemptive scheduling policy and a higher priority than the thread which was running when the interrupt
       occurred, then the waiting thread will preempt the interrupt routine and begin  to  run	immediately.   This  is  unlike  pthread_cond_sig-
       nal_int_np(3)  which causes the condition variable to be signaled at a safe point after the interrupt has completed.  pthread_cond_sig_pre-
       empt_int_np(3) avoids the possible latency which pthread_cond_signal_int_np(3) may introduce; however, a side effect of this is that during
       the  call  to  pthread_cond_sig_preempt_int_np(3)  other  threads  may  run  if	a preemption occurs; thus, once an interrupt routine calls
       pthread_cond_sig_preempt_int_np(3) it can no longer rely on any assumptions of exclusivity or atomicity which  are  typically  provided	by
       interrupt routines.  Furthermore, once the call to pthread_cond_sig_preempt_int_np(3) is made, in addition to other threads running, subse-
       quent interrupts may be delivered at any time as well (that is, they will not be blocked until the current interrupt completes).  For  this
       reason, it is recommended that pthread_cond_sig_preempt_int_np(3) be called as the last statement in the interrupt routine.

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 by cond is not a valid condition variable.

ERRORS
       None

RELATED INFORMATION
       Functions:      pthread_cond_broadcast(3),      pthread_cond_signal(3),	    pthread_cond_signal_int_np(3),	pthread_cond_timedwait(3),
       pthread_cond_wait(3)

       Manuals: Guide to DECthreads and Programmer's Guide

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														pthread_cond_sig_preempt_int_np(3)