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 7.1.2 July 7, 2010 NetBSD 7.1.2

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