max/embassy
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

executor: mark task_from_waker as safe.

Browse Source
This commit is contained in:
Dario Nieuwenhuis 2022-06-26 00:13:31 +02:00
parent a51df0dec6
commit 935def4a0b
2 changed files with 11 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
embassy/src/executor/raw/waker.rs
View File

@ -33,12 +33,18 @@ pub(crate) unsafe fn from_task(p: NonNull<TaskHeader>) -> Waker {
/// # Panics /// # Panics
/// ///
/// Panics if the waker is not created by the Embassy executor. /// Panics if the waker is not created by the Embassy executor.
pub unsafe fn task_from_waker(waker: &Waker) -> NonNull<TaskHeader> { pub fn task_from_waker(waker: &Waker) -> NonNull<TaskHeader> {
let hack: &WakerHack = mem::transmute(waker); // safety: OK because WakerHack has the same layout as Waker.
// This is not really guaranteed because the structs are `repr(Rust)`, it is
// indeed the case in the current implementation.
// TODO use waker_getters when stable. https://github.com/rust-lang/rust/issues/96992
let hack: &WakerHack = unsafe { mem::transmute(waker) };
if hack.vtable != &VTABLE { if hack.vtable != &VTABLE {
panic!("Found waker not created by the embassy executor. Consider enabling the `executor-agnostic` feature on the `embassy` crate.") panic!("Found waker not created by the embassy executor. Consider enabling the `executor-agnostic` feature on the `embassy` crate.")
} }
NonNull::new_unchecked(hack.data as *mut TaskHeader)
// safety: we never create a waker with a null data pointer.
unsafe { NonNull::new_unchecked(hack.data as *mut TaskHeader) }
} }
struct WakerHack { struct WakerHack {

4
embassy/src/waitqueue/waker.rs
View File

@ -22,7 +22,7 @@ impl WakerRegistration {
/// Register a waker. Overwrites the previous waker, if any. /// Register a waker. Overwrites the previous waker, if any.
pub fn register(&mut self, w: &Waker) { pub fn register(&mut self, w: &Waker) {
let w = unsafe { task_from_waker(w) }; let w = task_from_waker(w);
match self.waker { match self.waker {
// Optimization: If both the old and new Wakers wake the same task, do nothing. // Optimization: If both the old and new Wakers wake the same task, do nothing.
Some(w2) if w == w2 => {} Some(w2) if w == w2 => {}
@ -80,7 +80,7 @@ impl AtomicWaker {
/// Register a waker. Overwrites the previous waker, if any. /// Register a waker. Overwrites the previous waker, if any.
pub fn register(&self, w: &Waker) { pub fn register(&self, w: &Waker) {
let w = unsafe { task_from_waker(w) }; let w = task_from_waker(w);
self.waker.store(w.as_ptr(), Ordering::Relaxed); self.waker.store(w.as_ptr(), Ordering::Relaxed);
compiler_fence(Ordering::SeqCst); compiler_fence(Ordering::SeqCst);
} }