linux-kernel - Re: [PATCH v8 6/7] rust: Add read_poll

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Message-Id: <20250123.162953.1064418483128096795.fujita.tomonori@gmail.com>
Date: Thu, 23 Jan 2025 16:29:53 +0900 (JST)
From: FUJITA Tomonori <fujita.tomonori@...il.com>
To: aliceryhl@...gle.com
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Subject: Re: [PATCH v8 6/7] rust: Add read_poll_timeout functions

On Wed, 22 Jan 2025 21:14:00 +0100
Alice Ryhl <aliceryhl@...gle.com> wrote:

>> > +#[track_caller]
>> > +pub fn read_poll_timeout<Op, Cond, T: Copy>(
>>
>> I wonder if we can lift the `T: Copy` restriction and have `Cond` take
>> `&T` instead. I can see this being useful in many cases.
>>
>> I know that quite often `T` is just an integer so you'd want to pass by
>> value, but I think almost always `Cond` is a very simple closure so
>> inlining would take place and they won't make a performance difference.
> 
> Yeah, I think it should be
> 
> Cond: FnMut(&T) -> bool,
> 
> with FnMut as well.

Yeah, less restriction is better. I changed the code as follows:

#[track_caller]
pub fn read_poll_timeout<Op, Cond, T>(
    mut op: Op,
    mut cond: Cond,
    sleep_delta: Delta,
    timeout_delta: Delta,
) -> Result<T>
where
    Op: FnMut() -> Result<T>,
    Cond: FnMut(&T) -> bool,
{