20 /// Current state of a `Once`.
37     /// Returns whether the associated `Once` has been poisoned.
39     /// Once an initialization routine for a `Once` has panicked it will forever
49     /// Returns whether the associated `Once` has successfully executed a
64 /// # Differences from the standard library `Once`
75 /// use parking_lot::Once;
77 /// static START: Once = Once::new();
83 pub struct Once(AtomicU8);  struct
85 impl Once {  impl
86     /// Creates a new `Once` value.
88     pub const fn new() -> Once {  in new()
89         Once(AtomicU8::new(0))  in new()
92     /// Returns the current state of this `Once`.
107     /// Performs an initialization routine once and only once. The given closure
124     /// use parking_lot::Once;
127     /// static INIT: Once = Once::new();
130     /// // in a synchronized fashion (e.g. write once or read all) then we're
133     /// // This function will only call `expensive_computation` once, and will
152     /// The closure `f` will only be executed once if this is called
154     /// it will *poison* this `Once` instance, causing all future invocations of
171     /// If this `Once` has been poisoned (some initialization panicked) then
176     /// state of this `Once` (whether initialization has previously panicked or
221                 panic!("Once instance has previously been poisoned");  in call_once_slow()
281         struct PanicGuard<'a>(&'a Once);  in call_once_slow()
285                 let once = self.0;  in call_once_slow()  localVariable
286                 let state = once.0.swap(POISON_BIT, Ordering::Release);  in call_once_slow()
288                     let addr = once as *const _ as usize;  in call_once_slow()
318 impl Default for Once {  implementation
320     fn default() -> Once {  in default()
321         Once::new()  in default()
325 impl fmt::Debug for Once {  implementation
327         f.debug_struct("Once")  in fmt()
335     use crate::Once;
342         static O: Once = Once::new();  in smoke_once()
352         static O: Once = Once::new();  in stampede_once()
388         static O: Once = Once::new();  in poison_bad()
390         // poison the once  in poison_bad()
410         // once any success happens, we stop propagating the poison  in poison_bad()
416         static O: Once = Once::new();  in wait_for_force_to_finish()
418         // poison the once  in wait_for_force_to_finish()
424         // make sure someone's waiting inside the once via a force  in wait_for_force_to_finish()
437         // put another waiter on the once  in wait_for_force_to_finish()
454         static O: Once = Once::new();  in test_once_debug()
456         assert_eq!(format!("{:?}", O), "Once { state: New }");  in test_once_debug()