pthread_cond_sig_preempt_int_np man page on DigitalUNIX

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pthread_cond_sig_preempt_int_np(3)	    pthread_cond_sig_preempt_int_np(3)

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

       #include <pthread.h>

       int pthread_cond_sig_preempt_int_np(
	       pthread_cond_t *cond );

       DECthreads POSIX 1003.1c Library (

       Interfaces documented on this reference page conform to industry	 stan‐
       dards as follows:

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

       Condition variable to be signaled.

       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‐

       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

       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.

       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.


       Functions:      pthread_cond_broadcast(3),      pthread_cond_signal(3),
       pthread_cond_signal_int_np(3),		    pthread_cond_timedwait(3),

       Manuals: Guide to DECthreads and Programmer's Guide


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