diff options
| -rw-r--r-- | library/std/src/sys/sync/once/futex.rs | 10 | ||||
| -rw-r--r-- | library/std/src/sys/sync/once/queue.rs | 11 |
2 files changed, 12 insertions, 9 deletions
diff --git a/library/std/src/sys/sync/once/futex.rs b/library/std/src/sys/sync/once/futex.rs index 539f0fe89ea..407fdcebcf5 100644 --- a/library/std/src/sys/sync/once/futex.rs +++ b/library/std/src/sys/sync/once/futex.rs @@ -8,16 +8,18 @@ use crate::sys::futex::{Futex, Primitive, futex_wait, futex_wake_all}; // This means we only need one atomic value with 4 states: /// No initialization has run yet, and no thread is currently using the Once. -const INCOMPLETE: Primitive = 0; +const INCOMPLETE: Primitive = 3; /// Some thread has previously attempted to initialize the Once, but it panicked, /// so the Once is now poisoned. There are no other threads currently accessing /// this Once. -const POISONED: Primitive = 1; +const POISONED: Primitive = 2; /// Some thread is currently attempting to run initialization. It may succeed, /// so all future threads need to wait for it to finish. -const RUNNING: Primitive = 2; +const RUNNING: Primitive = 1; /// Initialization has completed and all future calls should finish immediately. -const COMPLETE: Primitive = 3; +/// By choosing this state as the all-zero state the `is_completed` check can be +/// a bit faster on some platforms. +const COMPLETE: Primitive = 0; // An additional bit indicates whether there are waiting threads: diff --git a/library/std/src/sys/sync/once/queue.rs b/library/std/src/sys/sync/once/queue.rs index 6a2ab0dcf1b..49e15d65f25 100644 --- a/library/std/src/sys/sync/once/queue.rs +++ b/library/std/src/sys/sync/once/queue.rs @@ -74,11 +74,12 @@ pub struct OnceState { } // Four states that a Once can be in, encoded into the lower bits of -// `state_and_queue` in the Once structure. -const INCOMPLETE: usize = 0x0; -const POISONED: usize = 0x1; -const RUNNING: usize = 0x2; -const COMPLETE: usize = 0x3; +// `state_and_queue` in the Once structure. By choosing COMPLETE as the all-zero +// state the `is_completed` check can be a bit faster on some platforms. +const INCOMPLETE: usize = 0x3; +const POISONED: usize = 0x2; +const RUNNING: usize = 0x1; +const COMPLETE: usize = 0x0; // Mask to learn about the state. All other bits are the queue of waiters if // this is in the RUNNING state. |