If the lock specified by lockp is immediately available
(can be acquired without sleeping)
the SLEEP_TRYLOCK function acquires the lock.
If the lock is not immediately available,
SLEEP_TRYLOCK returns without acquiring the lock.
Arguments
lockp
Pointer to the sleep lock to be acquired.
Return values
SLEEP_TRYLOCK returns TRUE (a non-zero value)
if the lock is successfully acquired
or FALSE (zero) if the lock is not acquired.