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std: Doc blocking behavior of LazyLock methods

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Behnam Esfahbod 2024-01-11 15:55:50 -08:00 committed by Behnam Esfahbod
parent 62d7ed4a67
commit a596159dca
1 changed files with 15 additions and 6 deletions
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21
library/std/src/sync/lazy_lock.rs
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@ -20,6 +20,9 @@ union Data<T, F> {
/// A value which is initialized on the first access. /// A value which is initialized on the first access.
/// ///
/// This type is a thread-safe [`LazyCell`], and can be used in statics. /// This type is a thread-safe [`LazyCell`], and can be used in statics.
/// Since initialization may be called from multiple threads, any
/// dereferencing call will block the calling thread if another
/// initialization routine is currently running.
/// ///
/// [`LazyCell`]: crate::cell::LazyCell /// [`LazyCell`]: crate::cell::LazyCell
/// ///
@ -81,8 +84,7 @@ pub struct LazyLock<T, F = fn() -> T> {
} }
impl<T, F: FnOnce() -> T> LazyLock<T, F> { impl<T, F: FnOnce() -> T> LazyLock<T, F> {
/// Creates a new lazy value with the given initializing /// Creates a new lazy value with the given initializing function.
/// function.
#[inline] #[inline]
#[unstable(feature = "lazy_cell", issue = "109736")] #[unstable(feature = "lazy_cell", issue = "109736")]
pub const fn new(f: F) -> LazyLock<T, F> { pub const fn new(f: F) -> LazyLock<T, F> {
@ -134,9 +136,11 @@ impl<T, F: FnOnce() -> T> LazyLock<T, F> {
} }
} }
/// Forces the evaluation of this lazy value and /// Forces the evaluation of this lazy value and returns a reference to
/// returns a reference to result. This is equivalent /// result. This is equivalent to the `Deref` impl, but is explicit.
/// to the `Deref` impl, but is explicit. ///
/// This method will block the calling thread if another initialization
/// routine is currently running.
/// ///
/// # Examples /// # Examples
/// ///
@ -204,6 +208,11 @@ impl<T, F> Drop for LazyLock<T, F> {
impl<T, F: FnOnce() -> T> Deref for LazyLock<T, F> { impl<T, F: FnOnce() -> T> Deref for LazyLock<T, F> {
type Target = T; type Target = T;
/// Dereferences the value.
///
/// This method will block the calling thread if another initialization
/// routine is currently running.
///
#[inline] #[inline]
fn deref(&self) -> &T { fn deref(&self) -> &T {
LazyLock::force(self) LazyLock::force(self)
@ -232,7 +241,7 @@ impl<T: fmt::Debug, F> fmt::Debug for LazyLock<T, F> {
} }
// We never create a `&F` from a `&LazyLock<T, F>` so it is fine // We never create a `&F` from a `&LazyLock<T, F>` so it is fine
// to not impl `Sync` for `F` // to not impl `Sync` for `F`.
#[unstable(feature = "lazy_cell", issue = "109736")] #[unstable(feature = "lazy_cell", issue = "109736")]
unsafe impl<T: Sync + Send, F: Send> Sync for LazyLock<T, F> {} unsafe impl<T: Sync + Send, F: Send> Sync for LazyLock<T, F> {}
// auto-derived `Send` impl is OK. // auto-derived `Send` impl is OK.