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< / pre > < / div > < pre class = "rust" > < code > < span class = "attr" > #![cfg_attr(not(feature = < span class = "string" > " std" < / span > ), no_std)]
#![doc = < span class = "macro" > include_str!< / span > (< span class = "string" > " ../README.md" < / span > )]
< / span > < span class = "kw" > mod < / span > mutex;
< span class = "attr" > #[cfg(feature = < span class = "string" > " std" < / span > )]
< / span > < span class = "kw" > mod < / span > std;
< span class = "kw" > use < / span > core::marker::PhantomData;
< span class = "kw" > pub use < / span > < span class = "self" > self< / span > ::mutex::Mutex;
< span class = "doccomment" > /// Critical section token.
///
/// An instance of this type indicates that the current thread is executing code within a critical
/// section.
< / span > < span class = "attr" > #[derive(Clone, Copy, Debug)]
< / span > < span class = "kw" > pub struct < / span > CriticalSection< < span class = "lifetime" > ' cs< / span > > {
_private: PhantomData< < span class = "kw-2" > & < / span > < span class = "lifetime" > ' cs < / span > ()> ,
}
< span class = "kw" > impl< / span > < < span class = "lifetime" > ' cs< / span > > CriticalSection< < span class = "lifetime" > ' cs< / span > > {
< span class = "doccomment" > /// Creates a critical section token.
///
/// This method is meant to be used to create safe abstractions rather than being directly used
/// in applications.
///
/// # Safety
///
/// This must only be called when the current thread is in a critical section. The caller must
/// ensure that the returned instance will not live beyond the end of the critical section.
///
/// The caller must use adequate fences to prevent the compiler from moving the
/// instructions inside the critical section to the outside of it. Sequentially consistent fences are
/// suggested immediately after entry and immediately before exit from the critical section.
///
/// Note that the lifetime `' cs` of the returned instance is unconstrained. User code must not
/// be able to influence the lifetime picked for this type, since that might cause it to be
/// inferred to `' static`.
< / span > < span class = "attr" > #[inline(always)]
< / span > < span class = "kw" > pub unsafe fn < / span > new() -> < span class = "self" > Self < / span > {
CriticalSection {
_private: PhantomData,
}
}
}
< span class = "attr" > #[cfg(any(
all(feature = < span class = "string" > " restore-state-none" < / span > , feature = < span class = "string" > " restore-state-bool" < / span > ),
all(feature = < span class = "string" > " restore-state-none" < / span > , feature = < span class = "string" > " restore-state-u8" < / span > ),
all(feature = < span class = "string" > " restore-state-none" < / span > , feature = < span class = "string" > " restore-state-u16" < / span > ),
all(feature = < span class = "string" > " restore-state-none" < / span > , feature = < span class = "string" > " restore-state-u32" < / span > ),
all(feature = < span class = "string" > " restore-state-none" < / span > , feature = < span class = "string" > " restore-state-u64" < / span > ),
all(feature = < span class = "string" > " restore-state-bool" < / span > , feature = < span class = "string" > " restore-state-u8" < / span > ),
all(feature = < span class = "string" > " restore-state-bool" < / span > , feature = < span class = "string" > " restore-state-u16" < / span > ),
all(feature = < span class = "string" > " restore-state-bool" < / span > , feature = < span class = "string" > " restore-state-u32" < / span > ),
all(feature = < span class = "string" > " restore-state-bool" < / span > , feature = < span class = "string" > " restore-state-u64" < / span > ),
all(feature = < span class = "string" > " restore-state-u8" < / span > , feature = < span class = "string" > " restore-state-u16" < / span > ),
all(feature = < span class = "string" > " restore-state-u8" < / span > , feature = < span class = "string" > " restore-state-u32" < / span > ),
all(feature = < span class = "string" > " restore-state-u8" < / span > , feature = < span class = "string" > " restore-state-u64" < / span > ),
all(feature = < span class = "string" > " restore-state-u16" < / span > , feature = < span class = "string" > " restore-state-u32" < / span > ),
all(feature = < span class = "string" > " restore-state-u16" < / span > , feature = < span class = "string" > " restore-state-u64" < / span > ),
all(feature = < span class = "string" > " restore-state-u32" < / span > , feature = < span class = "string" > " restore-state-u64" < / span > ),
))]
< / span > < span class = "macro" > compile_error!< / span > (< span class = "string" > " You must set at most one of these Cargo features: restore-state-none, restore-state-bool, restore-state-u8, restore-state-u16, restore-state-u32, restore-state-u64" < / span > );
< span class = "attr" > #[cfg(not(any(
feature = < span class = "string" > " restore-state-bool" < / span > ,
feature = < span class = "string" > " restore-state-u8" < / span > ,
feature = < span class = "string" > " restore-state-u16" < / span > ,
feature = < span class = "string" > " restore-state-u32" < / span > ,
feature = < span class = "string" > " restore-state-u64"
< / span > )))]
< / span > < span class = "kw" > type < / span > RawRestoreStateInner = ();
< span class = "attr" > #[cfg(feature = < span class = "string" > " restore-state-bool" < / span > )]
< / span > < span class = "kw" > type < / span > RawRestoreStateInner = bool;
< span class = "attr" > #[cfg(feature = < span class = "string" > " restore-state-u8" < / span > )]
< / span > < span class = "kw" > type < / span > RawRestoreStateInner = u8;
< span class = "attr" > #[cfg(feature = < span class = "string" > " restore-state-u16" < / span > )]
< / span > < span class = "kw" > type < / span > RawRestoreStateInner = u16;
< span class = "attr" > #[cfg(feature = < span class = "string" > " restore-state-u32" < / span > )]
< / span > < span class = "kw" > type < / span > RawRestoreStateInner = u32;
< span class = "attr" > #[cfg(feature = < span class = "string" > " restore-state-u64" < / span > )]
< / span > < span class = "kw" > type < / span > RawRestoreStateInner = u64;
< span class = "comment" > // We have RawRestoreStateInner and RawRestoreState so that we don' t have to copypaste the docs 5 times.
// In the docs this shows as `pub type RawRestoreState = u8` or whatever the selected type is, because
// the " inner" type alias is private.
< / span > < span class = "doccomment" > /// Raw, transparent " restore state" .
///
/// This type changes based on which Cargo feature is selected, out of
/// - `restore-state-none` (default, makes the type be `()`)
/// - `restore-state-bool`
/// - `restore-state-u8`
/// - `restore-state-u16`
/// - `restore-state-u32`
/// - `restore-state-u64`
///
/// See [`RestoreState`].
///
/// User code uses [`RestoreState`] opaquely, critical section implementations
/// use [`RawRestoreState`] so that they can use the inner value.
< / span > < span class = "kw" > pub type < / span > RawRestoreState = RawRestoreStateInner;
< span class = "doccomment" > /// Opaque " restore state" .
///
/// Implementations use this to " carry over" information between acquiring and releasing
/// a critical section. For example, when nesting two critical sections of an
/// implementation that disables interrupts globally, acquiring the inner one won' t disable
/// the interrupts since they' re already disabled. The impl would use the restore state to " tell"
/// the corresponding release that it does *not* have to reenable interrupts yet, only the
/// outer release should do so.
///
/// User code uses [`RestoreState`] opaquely, critical section implementations
/// use [`RawRestoreState`] so that they can use the inner value.
< / span > < span class = "attr" > #[derive(Clone, Copy, Debug)]
< / span > < span class = "kw" > pub struct < / span > RestoreState(RawRestoreState);
< span class = "kw" > impl < / span > RestoreState {
< span class = "doccomment" > /// Create an invalid, dummy `RestoreState`.
///
/// This can be useful to avoid `Option` when storing a `RestoreState` in a
/// struct field, or a `static`.
///
/// Note that due to the safety contract of [`acquire`]/[`release`], you must not pass
/// a `RestoreState` obtained from this method to [`release`].
< / span > < span class = "kw" > pub const fn < / span > invalid() -> < span class = "self" > Self < / span > {
< span class = "attr" > #[cfg(not(any(
feature = < span class = "string" > " restore-state-bool" < / span > ,
feature = < span class = "string" > " restore-state-u8" < / span > ,
feature = < span class = "string" > " restore-state-u16" < / span > ,
feature = < span class = "string" > " restore-state-u32" < / span > ,
feature = < span class = "string" > " restore-state-u64"
< / span > )))]
< / span > < span class = "kw" > return < / span > < span class = "self" > Self< / span > (());
< span class = "attr" > #[cfg(feature = < span class = "string" > " restore-state-bool" < / span > )]
< / span > < span class = "kw" > return < / span > < span class = "self" > Self< / span > (< span class = "bool-val" > false< / span > );
< span class = "attr" > #[cfg(feature = < span class = "string" > " restore-state-u8" < / span > )]
< / span > < span class = "kw" > return < / span > < span class = "self" > Self< / span > (< span class = "number" > 0< / span > );
< span class = "attr" > #[cfg(feature = < span class = "string" > " restore-state-u16" < / span > )]
< / span > < span class = "kw" > return < / span > < span class = "self" > Self< / span > (< span class = "number" > 0< / span > );
< span class = "attr" > #[cfg(feature = < span class = "string" > " restore-state-u32" < / span > )]
< / span > < span class = "kw" > return < / span > < span class = "self" > Self< / span > (< span class = "number" > 0< / span > );
< span class = "attr" > #[cfg(feature = < span class = "string" > " restore-state-u64" < / span > )]
< / span > < span class = "kw" > return < / span > < span class = "self" > Self< / span > (< span class = "number" > 0< / span > );
}
}
< span class = "doccomment" > /// Acquire a critical section in the current thread.
///
/// This function is extremely low level. Strongly prefer using [`with`] instead.
///
/// Nesting critical sections is allowed. The inner critical sections
/// are mostly no-ops since they' re already protected by the outer one.
///
/// # Safety
///
/// - Each `acquire` call must be paired with exactly one `release` call in the same thread.
/// - `acquire` returns a " restore state" that you must pass to the corresponding `release` call.
/// - `acquire`/`release` pairs must be " properly nested" , ie it' s not OK to do `a=acquire(); b=acquire(); release(a); release(b);`.
/// - It is UB to call `release` if the critical section is not acquired in the current thread.
/// - It is UB to call `release` with a " restore state" that does not come from the corresponding `acquire` call.
/// - It must provide ordering guarantees at least equivalent to a [`core::sync::atomic::Ordering::Acquire`]
/// on a memory location shared by all critical sections, on which the `release` call will do a
/// [`core::sync::atomic::Ordering::Release`] operation.
< / span > < span class = "attr" > #[inline(always)]
< / span > < span class = "kw" > pub unsafe fn < / span > acquire() -> RestoreState {
< span class = "kw" > extern < / span > < span class = "string" > " Rust" < / span > {
< span class = "kw" > fn < / span > _critical_section_1_0_acquire() -> RawRestoreState;
}
< span class = "attr" > #[allow(clippy::unit_arg)]
< / span > RestoreState(_critical_section_1_0_acquire())
}
< span class = "doccomment" > /// Release the critical section.
///
/// This function is extremely low level. Strongly prefer using [`with`] instead.
///
/// # Safety
///
/// See [`acquire`] for the safety contract description.
< / span > < span class = "attr" > #[inline(always)]
< / span > < span class = "kw" > pub unsafe fn < / span > release(restore_state: RestoreState) {
< span class = "kw" > extern < / span > < span class = "string" > " Rust" < / span > {
< span class = "kw" > fn < / span > _critical_section_1_0_release(restore_state: RawRestoreState);
}
< span class = "attr" > #[allow(clippy::unit_arg)]
< / span > _critical_section_1_0_release(restore_state.< span class = "number" > 0< / span > )
}
< span class = "doccomment" > /// Execute closure `f` in a critical section.
///
/// Nesting critical sections is allowed. The inner critical sections
/// are mostly no-ops since they' re already protected by the outer one.
///
/// # Panics
///
/// This function panics if the given closure `f` panics. In this case
/// the critical section is released before unwinding.
< / span > < span class = "attr" > #[inline]
< / span > < span class = "kw" > pub fn < / span > with< R> (f: < span class = "kw" > impl < / span > FnOnce(CriticalSection) -> R) -> R {
< span class = "comment" > // Helper for making sure `release` is called even if `f` panics.
< / span > < span class = "kw" > struct < / span > Guard {
state: RestoreState,
}
< span class = "kw" > impl < / span > Drop < span class = "kw" > for < / span > Guard {
< span class = "attr" > #[inline(always)]
< / span > < span class = "kw" > fn < / span > drop(< span class = "kw-2" > & mut < / span > < span class = "self" > self< / span > ) {
< span class = "kw" > unsafe < / span > { release(< span class = "self" > self< / span > .state) }
}
}
< span class = "kw" > let < / span > state = < span class = "kw" > unsafe < / span > { acquire() };
< span class = "kw" > let < / span > _guard = Guard { state };
< span class = "kw" > unsafe < / span > { f(CriticalSection::new()) }
}
< span class = "doccomment" > /// Methods required for a critical section implementation.
///
/// This trait is not intended to be used except when implementing a critical section.
///
/// # Safety
///
/// Implementations must uphold the contract specified in [`crate::acquire`] and [`crate::release`].
< / span > < span class = "kw" > pub unsafe trait < / span > Impl {
< span class = "doccomment" > /// Acquire the critical section.
///
/// # Safety
///
/// Callers must uphold the contract specified in [`crate::acquire`] and [`crate::release`].
< / span > < span class = "kw" > unsafe fn < / span > acquire() -> RawRestoreState;
< span class = "doccomment" > /// Release the critical section.
///
/// # Safety
///
/// Callers must uphold the contract specified in [`crate::acquire`] and [`crate::release`].
< / span > < span class = "kw" > unsafe fn < / span > release(restore_state: RawRestoreState);
}
< span class = "doccomment" > /// Set the critical section implementation.
///
/// # Example
///
/// ```
/// # #[cfg(not(feature = " std" ))] // needed for `cargo test --features std`
/// # mod no_std {
/// use critical_section::RawRestoreState;
///
/// struct MyCriticalSection;
/// critical_section::set_impl!(MyCriticalSection);
///
/// unsafe impl critical_section::Impl for MyCriticalSection {
/// unsafe fn acquire() -> RawRestoreState {
/// // ...
/// }
///
/// unsafe fn release(restore_state: RawRestoreState) {
/// // ...
/// }
/// }
/// # }
< / span > < span class = "attr" > #[macro_export]
< / span > < span class = "macro" > macro_rules! < / span > set_impl {
(< span class = "macro-nonterminal" > $t< / span > : ty) => {
< span class = "attr" > #[no_mangle]
< / span > < span class = "kw" > unsafe fn < / span > _critical_section_1_0_acquire() -> < span class = "macro-nonterminal" > $crate::RawRestoreState < / span > {
< < span class = "macro-nonterminal" > $t < / span > < span class = "kw" > as < / span > < span class = "macro-nonterminal" > $crate::Impl< / span > > ::acquire()
}
< span class = "attr" > #[no_mangle]
< / span > < span class = "kw" > unsafe fn < / span > _critical_section_1_0_release(restore_state: < span class = "macro-nonterminal" > $crate::RawRestoreState< / span > ) {
< < span class = "macro-nonterminal" > $t < / span > < span class = "kw" > as < / span > < span class = "macro-nonterminal" > $crate::Impl< / span > > ::release(restore_state)
}
};
}
< / code > < / pre > < / div > < / section > < / main > < / body > < / html >
