NAME

RUN_ONCE - Run a function exactly once

SYNOPSIS



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 execution, 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)