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That only holds when the operation is issued from > outside the timer handler. > > The `start` operation returns a `HrTimerHandle`, and dropping the > handle cancels the timer with `hrtimer_cancel()`, which blocks until a > running handler has returned. When `start` is issued from within the > handler, the handle is also dropped within the handler, so the cancel > waits for the very handler that issues it, and the handler deadlocks. That's not always true, you can start timer and store its handle elsewhere. I think the proper wording is that "cancelling a timer from within the time= r handler will lead to deadlock". Best, Gary > > Note this in the state machine documentation. > > Signed-off-by: Andreas Hindborg > --- > rust/kernel/time/hrtimer.rs | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs > index bdb6aaa22839..2a9abc9f5d8c 100644 > --- a/rust/kernel/time/hrtimer.rs > +++ b/rust/kernel/time/hrtimer.rs > @@ -78,6 +78,8 @@ > //! handler returns, and a restart requested by the return value of the = handler is discarded in > //! favor of the `restart` operation. > //! > +//! =E2=9A=A0=EF=B8=8F Issuing the `start` operation from within the tim= er handler will lead to deadlock. > +//! > //! # Examples > //! > //! ## Using an intrusive timer living in a [`Box`]