pthread_condattr(3T)              SDK R4.11             pthread_condattr(3T)


NAME
       pthread_condattr: pthread_condattr_init, pthread_condattr_destroy,
       pthread_condattr_getpshared, pthread_condattr_setpshared - manipulate
       condition initialization attributes

SYNOPSIS
       #include <pthread.h>

       int pthread_condattr_init(pthread_condattr_t *attr);

       int pthread_condattr_destroy(pthread_condattr_t *attr);

       int pthread_condattr_getpshared(pthread_condattr_t *attr,
                                       int *pshared);

       int pthread_condattr_setpshared(pthread_condattr_t *attr,
                                       int pshared);

   where:
       attr     A pointer to a condition attributes object
       pshared  For pthread_condattr_getpshared(), a pointer to a location
                to store the process-shared attribute; for
                pthread_condattr_setpshared(), the new value of the process-
                shared attribute.

DESCRIPTION
       Condition attributes objects are used to control the initialization
       of conditions in a way similar to which thread attributes objects are
       used to control the creation of threads.

       DG/UX supports the process-shared attribute for condition variables.
       This attribute can have a value of 0 or 1.  A value of 0 (default)
       indicates that condition variables initialized with this condition
       attributes object are only allowed to be operated upon by threads
       within the the current process.  A value of 1 indicates that
       condition variables initialized with this condition attributes object
       are allowed to be operated upon by threads in all processes that have
       access to the memory in which the condition is allocated.  Whenever
       possible, the default value of 0 for the process-shared attribute
       should be used, as intraprocess condition variables are more
       efficient than interprocess condition variables.

       The pthread_condattr_init() function initializes a condition
       attributes object with the default value for the process-shared
       attribute.  In a call to pthread_cond_init(), passing a pointer to
       such a newly initialized condition attributes object is equivalent to
       passing a NULL pointer.

       The pthread_condattr_destroy() function destroys the condition
       attributes object pointed to by attr.

       The pthread_condattr_setpshared() function is used to set the
       process-shared attribute in an initialized attributes object pointed
       to by attr.  The pthread_condattr_getpshared() function returns the
       value of the process-shared attribute from the attributes object
       pointed to by attr.

       After a condition attributes object has been used in a call to
       pthread_cond_init(), it is no longer associated with the initialized
       condition variable.  The condition attributes object can be freely
       destroyed, modified, or used again to initialize another condition
       variable.

DIAGNOSTICS
   Returns
       If successful, pthread_condattr_init(),
       pthread_condattr_setpshared(), and pthread_condattr_destroy() return
       0.  Otherwise each returns -1 and sets errno to indicate the error.

       If successful, pthread_condattr_getpshared() returns 0 and stores the
       value of the process-shared attribute from the condition attributes
       object pointed to by attr into the location pointed to by pshared;
       otherwise it returns -1 and sets errno to indicate the error.

   Errors
       For each of the following conditions, pthread_condattr_destroy(),
       pthread_condattr_getpshared(), and pthread_condattr_setpshared()
       return -1 and set errno to the corresponding value:

       [EINVAL]  An invalid condition attributes object has been specified.
                 This occurs when DG/UX has detected that the condition
                 attributes object pointed to by attr has not been
                 initialized by a previous call to pthread_condattr_init()
                 or has been corrupted.

       For each of the following conditions, pthread_condattr_setpshared()
       returns -1 and sets errno to the corresponding value:

       [EINVAL]  The value given by pshared is not 0 or 1.

SEE ALSO
       pthread_cond_init(3T), pthread_cond_wait(3T),
       pthread_cond_timedwait(3T), pthread_cond_signal(3T),
       pthread_cond_broadcast(3T), pthread_mutexattr_init(3T),
       pthread_mutex_init(3T).

NOTES
       The DG/UX system defines the symbol {_POSIX_THREADS_PROCESS_SHARED},
       indicating that it supports the process-shared attribute for mutexes
       and condition variables.

       An application need not be multi-threaded to use process-shared
       condition variables.  However, it must compile and link against the
       thread interfaces.  Process-shared condition variables are
       significantly faster than traditional Unix semaphores, particularly
       in the uncontended cases.


Licensed material--property of copyright holder(s)