HP 3000 Manuals HP 3000 Manuals
Threads Synchronization and Communication
All threads in a process execute within a single address space and share
resources. When threads share resources in an unsynchronized way,
incorrect output can result from race conditions or thread scheduling
anomalies. The DCE Threads Service provides the following facilities and
routines to synchronize thread access to shared resources.
Mutexes (Mutual Exclusion Objects)
Mutexes are used to synchronize access by multiple threads to a shared
resource, allowing access by only one thread at a time. Routines for
creating and managing mutexes are:
pthread_mutex_init(mutex,attr)
pthread_mutex_destroy(mutex)
pthread_mutex_lock(mutex)
pthread_mutex_trylock(mutex)
pthread_mutex_unlock(mutex)
Condition Variables
Condition variables provide an explicit communication vehicle between
threads. A condition variable is a shared resource, and requires a mutex
to protect it. You use a condition variable to block one or more threads
until some condition becomes true, then any or all of the blocked threads
can be unblocked. Routines for creating and managing condition variables
are:
pthread_cond_init(cond,attr)
pthread_cond_broadcast(cond)
pthread_cond_signal(cond)
pthread_cond_wait(cond,mutex)
pthread_cond_destroy(cond)
Join Facility
The join facility is the simplest means of synchronizing threads, and
uses neither shared resources or mutexes. The join facility causes the
calling thread to wait until the specified thread finishes and returns a
status value to the calling thread. Routines for joining and detaching
threads are:
pthread_join(thread,status)
pthread_detach(thread)
Refer to the OSF DCE Application Development Guide (B3190-90036) and the
OSF DCE Application Development Reference (B3190-90032) for detailed
information on threads synchronization and communication.