rt: avoid early task shutdown #3870
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Tokio 1.7.0 introduced a change intended to eagerly shutdown newly spawned tasks if the runtime is in the process of shutting down. However, it introduced a bug where already spawned tasks could be shutdown too early, resulting in the potential introduction of deadlocks if tasks acquired mutexes in drop handlers. Fixes #3869
carllerche
changed the title
| @@ -9,6 +9,7 @@ | |||
| rust_2018_idioms, | |||
| unreachable_pub | |||
| )] | |||
| #![deny(unused_must_use)] | |||
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IMO, any unhandled Result values should result in a compilation failure.
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This is not directly related, so if needed, I can split it off to another PR.
| drop(p); | ||
| task.shutdown(); | ||
| return; | ||
| return Err(task); |
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The fix is to push the task.shutdown() call out to a point where we know if the task is newly spawned or not.
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I'll publish a release later today once CI passes. |
| fn drop(&mut self) { | ||
| println!("drop {} start", self.put_waker); | ||
| let mut lock = self.shared.lock().unwrap(); | ||
| if !self.put_waker { | ||
| lock.waker.take().unwrap().wake(); | ||
| } | ||
| drop(lock); | ||
| println!("drop {} stop", self.put_waker); | ||
| } |
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To reproduce this bug, it requires the task with put_waker==false(f2) to be dropped first to let it wakes up f1.
On my laptop it seems that the last spawned will always be dropped first. Do we have a guarantee about this behavior or some documents describing it? 🤔
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I don't think there's any way to get any guarantees about the drop order.
Darksonn
added
A-tokio
Tokio 1.7.0 introduced a change intended to eagerly shutdown newly
spawned tasks if the runtime is in the process of shutting down.
However, it introduced a bug where already spawned tasks could be
shutdown too early, resulting in the potential introduction of deadlocks
if tasks acquired mutexes in drop handlers.
Fixes #3869
The PR is based on the
tokio-1.7.xbranch and will be released as 1.7.1.