This introduces a module for dealing with interrupt-disabled contexts,
including the ability to enable and disable interrupts
(with_irqs_disabled()) - along with the ability to annotate functions as
expecting that IRQs are already disabled on the local CPU.
Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>
---
V2:
* Actually make it so that we check whether or not we have interrupts
disabled with debug assertions
* Fix issues in the documentation (added suggestions, missing periods, made
sure that all rustdoc examples compile properly)
* Pass IrqDisabled by value, not reference
* Ensure that IrqDisabled is !Send and !Sync using
PhantomData<(&'a (), *mut ())>
* Add all of the suggested derives from Benno Lossin
V3:
* Use `impl` for FnOnce bounds in with_irqs_disabled()
* Use higher-ranked trait bounds for the lifetime of with_irqs_disabled()
* Wording changes in the documentation for the module itself
V4:
* Use the actual unsafe constructor for IrqDisabled in
with_irqs_disabled()
* Fix comment style in with_irqs_disabled example
* Check before calling local_irq_restore() in with_irqs_disabled that
interrupts are still disabled.
It would have been nice to do this from a....
Drop implementation like I hoped, but I realized rust doesn't allow that
for types that implement Copy.
* Document that interrupts can't be re-enabled within the `cb` provided to
`with_irqs_disabled`, and link to the github issue I just filed about
this that describes the solution for this.
Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>
+/// Run the closure `cb` with interrupts disabled on the local CPU.
+///
+/// This creates an [`IrqDisabled`] token, which can be passed to functions that must be run
+/// without interrupts. Note that interrupts must be disabled for the entire duration of `cb`, they
+/// cannot be re-enabled. In the future, this may be expanded on
+/// [as documented here](https://github.com/Rust-for-Linux/linux/issues/1115).
+///
+/// # Examples
+///
+/// Using [`with_irqs_disabled`] to call a function that can only be called with interrupts
+/// disabled:
+///
+/// ```
+/// use kernel::irq::{IrqDisabled, with_irqs_disabled};
+///
+/// // Requiring interrupts be disabled to call a function
+/// fn dont_interrupt_me(_irq: IrqDisabled<'_>) {
+/// // When this token is available, IRQs are known to be disabled. Actions that rely on this
+/// // can be safely performed
+/// }
+///
+/// // Disabling interrupts. They'll be re-enabled once this closure completes.
+/// with_irqs_disabled(|irq| dont_interrupt_me(irq));
+/// ```
+#[inline]
+pub fn with_irqs_disabled<T>(cb: impl for<'a> FnOnce(IrqDisabled<'a>) -> T) -> T {
+ // SAFETY: FFI call with no special requirements
+ let flags = unsafe { bindings::local_irq_save() };
+
+ // SAFETY: We just disabled IRQs using `local_irq_save()`
+ let ret = cb(unsafe { IrqDisabled::new() });
+
+ // Confirm that IRQs are still enabled now that the callback has finished