linux-kernel - Re: [PATCH v5 05/14] rust: hrtimer: allow timer restart from timer handler

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Message-ID: <87bjwg9la4.fsf@kernel.org>
Date: Thu, 09 Jan 2025 14:20:03 +0100
From: Andreas Hindborg <a.hindborg@...nel.org>
To: "Guangbo Cui" <2407018371@...com>
Cc: "Miguel Ojeda" <ojeda@...nel.org>,  "Anna-Maria Behnsen"
 <anna-maria@...utronix.de>,  "Frederic Weisbecker" <frederic@...nel.org>,
  "Thomas Gleixner" <tglx@...utronix.de>,  "Danilo Krummrich"
 <dakr@...nel.org>,  "Alex Gaynor" <alex.gaynor@...il.com>,  "Boqun Feng"
 <boqun.feng@...il.com>,  "Gary Guo" <gary@...yguo.net>,  Björn Roy Baron
 <bjorn3_gh@...tonmail.com>,  "Benno Lossin" <benno.lossin@...ton.me>,
  "Alice Ryhl" <aliceryhl@...gle.com>,  "Trevor Gross" <tmgross@...ch.edu>,
  "Lyude Paul" <lyude@...hat.com>,  "Dirk Behme" <dirk.behme@...il.com>,
  "Daniel Almeida" <daniel.almeida@...labora.com>,
  <rust-for-linux@...r.kernel.org>,  <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 05/14] rust: hrtimer: allow timer restart from timer
 handler

"Guangbo Cui" <2407018371@...com> writes:

> On Tue, Dec 17, 2024 at 04:17:36PM +0100, Andreas Hindborg wrote:
>> This patch allows timer handlers to report that they want a timer to be
>> restarted after the timer handler has finished executing.
>>
>> Also update the `hrtimer` documentation to showcase the new feature.
>>
>> Signed-off-by: Andreas Hindborg <a.hindborg@...nel.org>
>> ---
>>  rust/kernel/time/hrtimer.rs     | 37 ++++++++++++++++++++++++++++++++++++-
>>  rust/kernel/time/hrtimer/arc.rs |  4 +---
>>  2 files changed, 37 insertions(+), 4 deletions(-)
>>
>> diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
>> index 178e33c1f656d2f834e45b004486f6e5fe1813dd..38a8251ea6ba4d84dadad009ed540c150bea4775 100644
>> --- a/rust/kernel/time/hrtimer.rs
>> +++ b/rust/kernel/time/hrtimer.rs
>> @@ -167,7 +167,7 @@ pub trait TimerCallback {
>>      type CallbackTargetParameter<'a>;
>>
>>      /// Called by the timer logic when the timer fires.
>> -    fn run(this: Self::CallbackTargetParameter<'_>)
>> +    fn run(this: Self::CallbackTargetParameter<'_>) -> TimerRestart
>>      where
>>          Self: Sized;
>>  }
>> @@ -262,6 +262,41 @@ unsafe fn start(self_ptr: *const Self, expires: Ktime) {
>>      }
>>  }
>>
>> +/// Restart policy for timers.
>> +pub enum TimerRestart {
>> +    /// Timer should not be restarted.
>> +    NoRestart,
>> +    /// Timer should be restarted.
>> +    Restart,
>> +}
>
> If we restart the timer, we may also want to `forward` the timer. I tried
> this series, and wrote some samples, found that it's inconvenient to write
> a loop timer.
>
> This is not a problem, just my feedback on the user experience.

Thanks! Lyude Paul has some patches that adds methods that operate
within timer context, including forwarding. I think they will send them
after this lands.


Best regards,
Andreas Hindborg