pthread_sleepon

Signal a sleeping thread

Synopsis:

#include <pthread.h>

int pthread_sleepon_signal(
       const volatile void * addr );

Arguments:

addr: The handle that the threads are waiting on. The value of addr is typically a data structure that controls a resource.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The pthread_sleepon_signal() function unblocks the highest priority thread waiting on addr.

You should use pthread_sleepon_broadcast() or pthread_sleepon_signal(), depending on the task you're doing:

Mapping a single predicate to one address

Use pthread_sleepon_signal().

If you use pthread_sleepon_broadcast(), you must recheck the predicate and reblock if necessary. The first thread to wake up owns the lock; all others must go back to sleep.

If you use pthread_sleepon_signal(), you don't have to recheck the predicate. One thread owns the lock at a time.

Mapping multiple predicates to one address

You need to use pthread_sleepon_broadcast() to wake up all blocked threads. You must recheck the predicates and reblock if necessary. You should try to map only one predicate to one address.

Don't use pthread_sleepon_signal() in this case; it could result in a deadlock.

Returns:

EOK: Success.
EINVAL: Invalid sleepon address.

Classification:

QNX Neutrino

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	Yes
Thread	Yes