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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)

SYNOPSIS
  #include <pthread.h>

  int pthread_cond_sig_preempt_int_np(
	  pthread_cond_t *cond );

LIBRARY
  DECthreads POSIX 1003.1c Library (libpthread.so)

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

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

PARAMETERS
  cond
      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_signal_int_np(3) which causes the
  condition variable to be signaled at a safe point after the interrupt has
  completed.  pthread_cond_sig_preempt_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, subsequent 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:

  0   Successful completion.

  [EINVAL]
      The value specified by cond is not a valid condition variable.

ERRORS
  None

SEE ALSO
  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

Index for Section 3

Alphabetical listing for P

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