RUN_ONCE(9)
- NetBSD Manual Pages
RUN_ONCE(9) NetBSD 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 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)
NetBSD 7.1_STABLE July 7, 2010 NetBSD 7.1_STABLE
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