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executor: fix unsoundness in InterruptExecutor::start.

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The initial closure is not actually called in the interrupt, so this is
illegally sending non-Send futures to the interrupt.

Remove the closure, and return a SendSpawner instead.
This commit is contained in:
Dario Nieuwenhuis 2022-04-25 22:09:04 +02:00
parent 52ed08cf95
commit b27feb0619
4 changed files with 22 additions and 28 deletions
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20
embassy/src/executor/arch/cortex_m.rs
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@ -1,7 +1,7 @@
use core::marker::PhantomData;
use core::ptr;
use super::{raw, Spawner};
use super::{raw, SendSpawner, Spawner};
use crate::interrupt::{Interrupt, InterruptExt};
/// Thread mode executor, using WFE/SEV.
@ -107,13 +107,13 @@ impl<I: Interrupt> InterruptExecutor<I> {
/// Start the executor.
///
/// The `init` closure is called from interrupt mode, with a [`Spawner`] that spawns tasks on
/// this executor. Use it to spawn the initial task(s). After `init` returns,
/// the interrupt is configured so that the executor starts running the tasks.
/// Once the executor is started, `start` returns.
/// This initializes the executor, configures and enables the interrupt, and returns.
/// The executor keeps running in the background through the interrupt.
///
/// To spawn more tasks later, you may keep copies of the [`Spawner`] (it is `Copy`),
/// for example by passing it as an argument to the initial tasks.
/// This returns a [`SendSpawner`] you can use to spawn tasks on it. A [`SendSpawner`]
/// is returned instead of a [`Spawner`] because the executor effectively runs in a
/// different "thread" (the interrupt), so spawning tasks on it is effectively
/// sending them.
///
/// This function requires `&'static mut self`. This means you have to store the
/// Executor instance in a place where it'll live forever and grants you mutable
@ -122,16 +122,16 @@ impl<I: Interrupt> InterruptExecutor<I> {
/// - a [Forever](crate::util::Forever) (safe)
/// - a `static mut` (unsafe)
/// - a local variable in a function you know never returns (like `fn main() -> !`), upgrading its lifetime with `transmute`. (unsafe)
pub fn start(&'static mut self, init: impl FnOnce(Spawner) + Send) {
pub fn start(&'static mut self) -> SendSpawner {
self.irq.disable();
init(self.inner.spawner());
self.irq.set_handler(|ctx| unsafe {
let executor = &*(ctx as *const raw::Executor);
executor.poll();
});
self.irq.set_handler_context(&self.inner as *const _ as _);
self.irq.enable();
self.inner.spawner().make_send()
}
}

10
examples/nrf/src/bin/multiprio.rs
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@ -124,17 +124,15 @@ fn main() -> ! {
let irq = interrupt::take!(SWI1_EGU1);
irq.set_priority(interrupt::Priority::P6);
let executor = EXECUTOR_HIGH.put(InterruptExecutor::new(irq));
executor.start(|spawner| {
unwrap!(spawner.spawn(run_high()));
});
let spawner = executor.start();
unwrap!(spawner.spawn(run_high()));
// Medium-priority executor: SWI0_EGU0, priority level 7
let irq = interrupt::take!(SWI0_EGU0);
irq.set_priority(interrupt::Priority::P7);
let executor = EXECUTOR_MED.put(InterruptExecutor::new(irq));
executor.start(|spawner| {
unwrap!(spawner.spawn(run_med()));
});
let spawner = executor.start();
unwrap!(spawner.spawn(run_med()));
// Low priority executor: runs in thread mode, using WFE/SEV
let executor = EXECUTOR_LOW.put(Executor::new());

10
examples/stm32f3/src/bin/multiprio.rs
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@ -124,17 +124,15 @@ fn main() -> ! {
let irq = interrupt::take!(UART4);
irq.set_priority(interrupt::Priority::P6);
let executor = EXECUTOR_HIGH.put(InterruptExecutor::new(irq));
executor.start(|spawner| {
unwrap!(spawner.spawn(run_high()));
});
let spawner = executor.start();
unwrap!(spawner.spawn(run_high()));
// Medium-priority executor: SWI0_EGU0, priority level 7
let irq = interrupt::take!(UART5);
irq.set_priority(interrupt::Priority::P7);
let executor = EXECUTOR_MED.put(InterruptExecutor::new(irq));
executor.start(|spawner| {
unwrap!(spawner.spawn(run_med()));
});
let spawner = executor.start();
unwrap!(spawner.spawn(run_med()));
// Low priority executor: runs in thread mode, using WFE/SEV
let executor = EXECUTOR_LOW.put(Executor::new());

10
examples/stm32f4/src/bin/multiprio.rs
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@ -124,17 +124,15 @@ fn main() -> ! {
let irq = interrupt::take!(UART4);
irq.set_priority(interrupt::Priority::P6);
let executor = EXECUTOR_HIGH.put(InterruptExecutor::new(irq));
executor.start(|spawner| {
unwrap!(spawner.spawn(run_high()));
});
let spawner = executor.start();
unwrap!(spawner.spawn(run_high()));
// Medium-priority executor: SWI0_EGU0, priority level 7
let irq = interrupt::take!(UART5);
irq.set_priority(interrupt::Priority::P7);
let executor = EXECUTOR_MED.put(InterruptExecutor::new(irq));
executor.start(|spawner| {
unwrap!(spawner.spawn(run_med()));
});
let spawner = executor.start();
unwrap!(spawner.spawn(run_med()));
// Low priority executor: runs in thread mode, using WFE/SEV
let executor = EXECUTOR_LOW.put(Executor::new());