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io: fix possible I/O resource hang (#6134)

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Use a per-resource tick instead of a single global tick counter. This
prevents the hang issue described by #6133.

Fixes: #6133
This commit is contained in:
Carl Lerche 2023-11-08 14:05:06 -08:00 committed by GitHub
parent 8ec3e0d94d
commit 30b2eb17c8
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 9 additions and 12 deletions
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11
tokio/src/runtime/io/driver.rs
View File

@ -18,10 +18,6 @@ use std::time::Duration;
/// I/O driver, backed by Mio.
pub(crate) struct Driver {
/// Tracks the number of times `turn` is called. It is safe for this to wrap
/// as it is mostly used to determine when to call `compact()`.
tick: u8,
/// True when an event with the signal token is received
signal_ready: bool,
@ -77,7 +73,7 @@ pub(super) enum Direction {
}
pub(super) enum Tick {
Set(u8),
Set,
Clear(u8),
}
@ -102,7 +98,6 @@ impl Driver {
let registry = poll.registry().try_clone()?;
let driver = Driver {
tick: 0,
signal_ready: false,
events: mio::Events::with_capacity(nevents),
poll,
@ -145,8 +140,6 @@ impl Driver {
fn turn(&mut self, handle: &Handle, max_wait: Option<Duration>) {
debug_assert!(!handle.registrations.is_shutdown(&handle.synced.lock()));
self.tick = self.tick.wrapping_add(1);
handle.release_pending_registrations();
let events = &mut self.events;
@ -184,7 +177,7 @@ impl Driver {
// an `Arc<ScheduledIo>` so we can safely cast this to a ref.
let io: &ScheduledIo = unsafe { &*ptr };
io.set_readiness(Tick::Set(self.tick), |curr| curr | ready);
io.set_readiness(Tick::Set, |curr| curr | ready);
io.wake(ready);
ready_count += 1;

10
tokio/src/runtime/io/scheduled_io.rs
View File

@ -219,17 +219,21 @@ impl ScheduledIo {
let current_readiness = Ready::from_usize(current);
let new = f(current_readiness);
let next = match tick {
Tick::Set(t) => TICK.pack(t as usize, new.as_usize()),
let new_tick = match tick {
Tick::Set => {
let current = TICK.unpack(current);
current.wrapping_add(1) % (TICK.max_value() + 1)
}
Tick::Clear(t) => {
if TICK.unpack(current) as u8 != t {
// Trying to clear readiness with an old event!
return;
}
TICK.pack(t as usize, new.as_usize())
t as usize
}
};
let next = TICK.pack(new_tick, new.as_usize());
match self
.readiness