Experimental PR for introducing klint #958
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| @@ -185,6 +185,7 @@ impl<'a, Out, F: FnMut() -> Result<Out> + Send + 'a> SocketFuture<'a, Out, F> { | |||
| /// | |||
| /// If the state matches the one we're waiting on, we wake up the task so that the future can be | |||
| /// polled again. | |||
| #[klint::preempt_count(expect = 0..)] // This function can be called from `wake_up` which must noy sleep. | |||
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nit:
| #[klint::preempt_count(expect = 0..)] // This function can be called from `wake_up` which must noy sleep. | |
| #[klint::preempt_count(expect = 0..)] // This function can be called from `wake_up` which must not sleep. |
| @@ -83,18 +85,21 @@ pub fn ref_waker<T: 'static + ArcWake>(w: Arc<T>) -> Waker { | |||
| ) | |||
| } | |||
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| #[klint::preempt_count(expect = 0..)] // Required as `Waker::clone` must not sleep. | |||
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Why Waker::clone must not sleep, could you elaborate?
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It is called by the callback passed to init_waitqueue_func_entry, which isn't allowed to sleep.
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Make senses, however, why do we need clone in wake_callback?
/me goes to search PR history
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Of course @wedsonaf may know the answer ;-)
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Looks like this is done to invoke the waker after unlocking the mutex protecting the waker is released. I would expect this is to prevent a deadlock or something like that.
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Looks to me that we can just do the following
if let Some(mut guard) = s.waker.try_lock() {
if let Some(w) = guard.take() {
drop(guard);
w.wake();
return 1;
}
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Yeah, that's what I suggested in the meeting. But I didn't make the change because I think the whole NoWaitLock<Option<Waker>> thing should be replaced with AtomicWaker instead.
This is purely experimental and for demonstration purpose!
How to test it out:
cargo build --release)export LD_LIBRARY_PATH=$(rustup run 1.66.0 bash -c "echo \$LD_LIBRARY_PATH")make RUSTC=<path to klint binary>on kernel tree