run_once(9) [netbsd man page]

RUN_ONCE(9)						   BSD Kernel Developer's Manual					       RUN_ONCE(9)

NAME

     RUN_ONCE -- Run a function exactly once

SYNOPSIS

     #include <sys/once.h>

     ONCE_DECL(control);

     int
     RUN_ONCE(once_t *control, int (*init_func)(void));

DESCRIPTION

     RUN_ONCE() provides a functionality similar to pthread_once(3).  It ensures that, for a given control, init_func() is executed (successfully)
     exactly once.  It is considered as a successful execution if and only if init_func() returned 0.  As long as there was no successful execu-
     tion, RUN_ONCE() will try again each time it is called.

     RUN_ONCE() can sleep if it's called concurrently.

RETURN VALUES

     On failure, RUN_ONCE() returns what init_func() returned.	Otherwise, it returns 0.

EXAMPLES

     The following example shows how RUN_ONCE() is used.  Regardless of how many times some_func() is executed, init_func() will be executed
     exactly once.

     static int
     init_func(void)
     {

	     /*
	      * do some initialization.
	      */

	     return 0; /* success */
     }

     int
     some_func(void)
     {
	     static ONCE_DECL(control);

	     RUN_ONCE(&control, init_func);

	     /*
	      * we are sure that init_func has already been completed here.
	      */
     }

SEE ALSO

     pthread_once(3), condvar(9), intro(9)

BSD
								   July 7, 2010 							       BSD

PTHREAD_ONCE(3) 					   BSD Library Functions Manual 					   PTHREAD_ONCE(3)

NAME

     pthread_once -- dynamic package initialization

SYNOPSIS

     #include <pthread.h>

     pthread_once_t once_control = PTHREAD_ONCE_INIT;

     int
     pthread_once(pthread_once_t *once_control, void (*init_routine)(void));

DESCRIPTION

     The first call to pthread_once() by any thread in a process, with a given once_control, will call the init_routine() with no arguments.  Sub-
     sequent calls to pthread_once() with the same once_control will not call the init_routine().  On return from pthread_once(), it is guaranteed
     that init_routine() has completed.  The once_control parameter is used to determine whether the associated initialization routine has been
     called.

     The function pthread_once() is not a cancellation point.  However, if init_routine() is a cancellation point and is cancelled, the effect on
     once_control is as if pthread_once() was never called.

     The constant PTHREAD_ONCE_INIT is defined by header <pthread.h>.

     The behavior of pthread_once() is undefined if once_control has automatic storage duration or is not initialized by PTHREAD_ONCE_INIT.

RETURN VALUES

     If successful, the pthread_once() function will return zero.  Otherwise, an error number will be returned to indicate the error.

ERRORS

     None.

STANDARDS

     pthread_once() conforms to ISO/IEC 9945-1:1996 (``POSIX.1'').

BSD
								   April 4, 1996							       BSD