pthread_cond_sig_preempt_int_np(3)pthread_cond_sig_preempt_int_np(3)NAMEpthread_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 stan‐
dards 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 prior‐
ities.
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_sig‐
nal_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 assump‐
tions of exclusivity or atomicity which are typically provided by
interrupt routines. Furthermore, once the call to pthread_cond_sig_pre‐
empt_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 con‐
dition 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
pthread_cond_sig_preempt_int_np(3)