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hal-common: remove Pin in PeripheralMutex

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This commit is contained in:
Dario Nieuwenhuis
2021-07-29 14:08:32 +02:00
parent de207764ae
commit af87031d62
7 changed files with 171 additions and 197 deletions
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130
embassy-hal-common/src/peripheral.rs
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@@ -1,6 +1,5 @@
use core::cell::UnsafeCell;
use core::marker::{PhantomData, PhantomPinned};
use core::pin::Pin;
use core::marker::PhantomData;
use core::mem::MaybeUninit;
use cortex_m::peripheral::scb::VectActive;
use cortex_m::peripheral::{NVIC, SCB};
@@ -10,23 +9,23 @@ use embassy::interrupt::{Interrupt, InterruptExt};
///
/// It needs to be `Send` because `&mut` references are sent back and forth between the 'thread' which owns the `PeripheralMutex` and the interrupt,
/// and `&mut T` is only `Send` where `T: Send`.
///
/// It also requires `'static` to be used safely with `PeripheralMutex::register_interrupt`,
/// because although `Pin` guarantees that the memory of the state won't be invalidated,
/// it doesn't guarantee that the lifetime will last.
pub trait PeripheralState: Send {
type Interrupt: Interrupt;
fn on_interrupt(&mut self);
}
pub struct PeripheralMutex<S: PeripheralState> {
state: UnsafeCell<S>,
pub struct StateStorage<S>(MaybeUninit<S>);
irq_setup_done: bool,
impl<S> StateStorage<S> {
pub fn new() -> Self {
Self(MaybeUninit::uninit())
}
}
pub struct PeripheralMutex<'a, S: PeripheralState> {
state: *mut S,
_phantom: PhantomData<&'a mut S>,
irq: S::Interrupt,
_not_send: PhantomData<*mut ()>,
_pinned: PhantomPinned,
}
/// Whether `irq` can be preempted by the current interrupt.
@@ -50,58 +49,45 @@ pub(crate) fn can_be_preempted(irq: &impl Interrupt) -> bool {
}
}
impl<S: PeripheralState + 'static> PeripheralMutex<S> {
/// Registers `on_interrupt` as the wrapped interrupt's interrupt handler and enables it.
///
/// This requires this `PeripheralMutex`'s `PeripheralState` to live for `'static`,
/// because `Pin` only guarantees that it's memory won't be repurposed,
/// not that it's lifetime will last.
///
/// To use non-`'static` `PeripheralState`, use the unsafe `register_interrupt_unchecked`.
///
/// Note: `'static` doesn't mean it _has_ to live for the entire program, like an `&'static T`;
/// it just means it _can_ live for the entire program - for example, `u8` lives for `'static`.
pub fn register_interrupt(self: Pin<&mut Self>) {
// SAFETY: `S: 'static`, so there's no way it's lifetime can expire.
unsafe { self.register_interrupt_unchecked() }
}
}
impl<S: PeripheralState> PeripheralMutex<S> {
impl<'a, S: PeripheralState> PeripheralMutex<'a, S> {
/// Create a new `PeripheralMutex` wrapping `irq`, with the initial state `state`.
pub fn new(state: S, irq: S::Interrupt) -> Self {
///
/// self requires `state` to live for `'static`, because if the `PeripheralMutex` is leaked, the
/// interrupt won't be disabled, which may try accessing the state at any time. To use non-`'static`
/// state, see [`Self::new_unchecked`].
///
/// Registers `on_interrupt` as the `irq`'s handler, and enables it.
pub fn new(storage: &'a mut StateStorage<S>, state: S, irq: S::Interrupt) -> Self
where
'a: 'static,
{
// safety: safe because state is `'static`.
unsafe { Self::new_unchecked(storage, state, irq) }
}
/// Create a `PeripheralMutex` without requiring the state is `'static`.
///
/// See also [`Self::new`].
///
/// # Safety
/// The created instance must not be leaked (its `drop` must run).
pub unsafe fn new_unchecked(
storage: &'a mut StateStorage<S>,
state: S,
irq: S::Interrupt,
) -> Self {
if can_be_preempted(&irq) {
panic!("`PeripheralMutex` cannot be created in an interrupt with higher priority than the interrupt it wraps");
}
Self {
irq,
irq_setup_done: false,
let state_ptr = storage.0.as_mut_ptr();
state: UnsafeCell::new(state),
_not_send: PhantomData,
_pinned: PhantomPinned,
}
}
// Safety: The pointer is valid and not used by anyone else
// because we have the `&mut StateStorage`.
state_ptr.write(state);
/// Registers `on_interrupt` as the wrapped interrupt's interrupt handler and enables it.
///
/// # Safety
/// The lifetime of any data in `PeripheralState` that is accessed by the interrupt handler
/// must not end without `Drop` being called on this `PeripheralMutex`.
///
/// This can be accomplished by either not accessing any data with a lifetime in `on_interrupt`,
/// or making sure that nothing like `mem::forget` is used on the `PeripheralMutex`.
// TODO: this name isn't the best.
pub unsafe fn register_interrupt_unchecked(self: Pin<&mut Self>) {
let this = self.get_unchecked_mut();
if this.irq_setup_done {
return;
}
this.irq.disable();
this.irq.set_handler(|p| {
irq.disable();
irq.set_handler(|p| {
// Safety: it's OK to get a &mut to the state, since
// - We checked that the thread owning the `PeripheralMutex` can't preempt us in `new`.
// Interrupts' priorities can only be changed with raw embassy `Interrupts`,
@@ -110,23 +96,24 @@ impl<S: PeripheralState> PeripheralMutex<S> {
let state = unsafe { &mut *(p as *mut S) };
state.on_interrupt();
});
this.irq
.set_handler_context((&mut this.state) as *mut _ as *mut ());
this.irq.enable();
irq.set_handler_context(state_ptr as *mut ());
irq.enable();
this.irq_setup_done = true;
Self {
irq,
state: state_ptr,
_phantom: PhantomData,
}
}
pub fn with<R>(self: Pin<&mut Self>, f: impl FnOnce(&mut S) -> R) -> R {
let this = unsafe { self.get_unchecked_mut() };
this.irq.disable();
pub fn with<R>(&mut self, f: impl FnOnce(&mut S) -> R) -> R {
self.irq.disable();
// Safety: it's OK to get a &mut to the state, since the irq is disabled.
let state = unsafe { &mut *this.state.get() };
let state = unsafe { &mut *self.state };
let r = f(state);
this.irq.enable();
self.irq.enable();
r
}
@@ -152,9 +139,14 @@ impl<S: PeripheralState> PeripheralMutex<S> {
}
}
impl<S: PeripheralState> Drop for PeripheralMutex<S> {
impl<'a, S: PeripheralState> Drop for PeripheralMutex<'a, S> {
fn drop(&mut self) {
self.irq.disable();
self.irq.remove_handler();
// safety:
// - we initialized the state in `new`, so we know it's initialized.
// - the irq is disabled, so it won't preempt us while dropping.
unsafe { self.state.drop_in_place() }
}
}