From: Andreas Hindborg <nmi@metaspace.dk>
To: Alice Ryhl <aliceryhl@google.com>
Cc: tj@kernel.org, alex.gaynor@gmail.com, benno.lossin@proton.me,
bjorn3_gh@protonmail.com, boqun.feng@gmail.com, gary@garyguo.net,
jiangshanlai@gmail.com, linux-kernel@vger.kernel.org,
ojeda@kernel.org, patches@lists.linux.dev,
rust-for-linux@vger.kernel.org, wedsonaf@gmail.com
Subject: Re: [PATCH v1 0/7] Bindings for the workqueue
Date: Tue, 23 May 2023 16:08:20 +0200 [thread overview]
Message-ID: <87mt1vdtq1.fsf@metaspace.dk> (raw)
In-Reply-To: <20230517222219.3191560-1-aliceryhl@google.com>
Alice Ryhl <aliceryhl@google.com> writes:
> On Wed, 17 May 2023 11:48:19 -1000, Tejun Heo wrote:
>> I tried to read the patches but am too dumb to understand much.
>
> The patch is more complicated than I would have liked, unfortunately.
> However, as I mentioned in the cover letter, simplifications should be
> on their way.
>
> Luckily, using the workqueue bindings is simpler than the bindings
> themselves.
>
>> Any chance you can provide some examples so that I can at least
>> imagine how workqueue would be used from rust side?
>
> Yes, of course!
If you have bandwidth for it, it would be awesome to see some examples
in the series as well (for /samples/rust).
BR Andreas
>
> The simplest way to use the workqueue is to use the `try_spawn` method
> introduced by the last patch in the series. With this function, you just
> pass a function pointer to the `try_spawn` method, and it schedules the
> function for execution. Unfortunately this allocates memory, making it
> a fallible operation.
>
> To avoid allocation memory, we do something else. As an example, we can
> look at the Rust binder driver that I am currently working on. Here is
> how it will be used in the binder driver: First, the `Process` struct
> will be given a `work_struct` field:
>
> #[pin_data]
> pub(crate) struct Process {
> // Work node for deferred work item.
> #[pin]
> defer_work: Work<Arc<Process>>,
>
> // Other fields follow...
> }
>
> Here, we use the type `Work<Arc<Process>>` for our field. This type is
> the Rust wrapper for `work_struct`. The generic parameter to `Work`
> should be the pointer type used to access `Process`, and in this case it
> is `Arc<Process>`. The pointer type `Arc` is used for reference
> counting, and its a pointer type that owns a ref-count to the inner
> value. (So e.g., it decrements the ref-cout when the arc goes out of
> scope.) Arc is an abbreviation of "atomic reference count". This means
> that while it is enqueued in the workqueue, the workqueue owns a
> ref-count to the process.
>
> Next, binder will use the `impl_has_work!` macro to declare that it
> wants to use `defer_work` as its `work_struct` field. That looks like
> this:
>
> kernel::impl_has_work! {
> impl HasWork<Arc<Process>> for Process { self.defer_work }
> }
>
> To define the code that should run when the work item is executed on the
> workqueue, binder does the following:
>
> impl workqueue::ArcWorkItem for Process {
> fn run(self: Arc<Process>) {
> // this runs when the work item is executed
> }
> }
>
> Finally to schedule it to the system workqueue, it does the following:
>
> let _ = workqueue::system().enqueue(process);
>
> Here, the `enqueue` call is fallible, since it might fail if the process
> has already been enqueued to a work queue. However, binder just uses
> `let _ =` to ignore the failure, since it doesn't need to do anything
> special in that case.
>
> I hope that helps, and let me know if you have any further questions.
>
> Alice
next prev parent reply other threads:[~2023-05-23 14:11 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-17 20:31 [PATCH v1 0/7] Bindings for the workqueue Alice Ryhl
2023-05-17 20:31 ` [PATCH v1 1/7] rust: workqueue: add low-level workqueue bindings Alice Ryhl
2023-05-18 14:51 ` Martin Rodriguez Reboredo
2023-05-19 9:40 ` Alice Ryhl
2023-05-19 12:04 ` Martin Rodriguez Reboredo
2023-05-23 10:03 ` Alice Ryhl
2023-05-30 8:26 ` Andreas Hindborg
2023-05-17 20:31 ` [PATCH v1 2/7] rust: add offset_of! macro Alice Ryhl
2023-05-18 14:51 ` Martin Rodriguez Reboredo
2023-05-23 15:48 ` Gary Guo
2023-05-24 12:26 ` Alice Ryhl
2023-05-30 8:40 ` Andreas Hindborg
2023-05-17 20:31 ` [PATCH v1 3/7] rust: sync: add `Arc::{from_raw, into_raw}` Alice Ryhl
2023-05-18 14:51 ` Martin Rodriguez Reboredo
2023-05-23 15:43 ` Gary Guo
2023-05-24 11:19 ` Alice Ryhl
2023-05-24 10:20 ` Andreas Hindborg
2023-05-24 11:11 ` Alice Ryhl
2023-05-25 7:45 ` Andreas Hindborg
2023-05-25 16:32 ` Gary Guo
2023-05-30 7:23 ` Andreas Hindborg
2023-05-17 20:31 ` [PATCH v1 4/7] rust: workqueue: define built-in queues Alice Ryhl
2023-05-18 14:52 ` Martin Rodriguez Reboredo
2023-05-25 11:40 ` Andreas Hindborg
2023-05-31 14:02 ` Alice Ryhl
2023-06-02 10:23 ` Andreas Hindborg (Samsung)
2023-05-17 20:31 ` [PATCH v1 5/7] rust: workqueue: add helper for defining work_struct fields Alice Ryhl
2023-05-18 23:18 ` Martin Rodriguez Reboredo
2023-05-24 14:50 ` Benno Lossin
2023-05-30 8:44 ` Andreas Hindborg
2023-05-31 9:00 ` Alice Ryhl
2023-05-31 10:18 ` Andreas Hindborg
2023-05-17 20:31 ` [PATCH v1 6/7] rust: workqueue: add safe API to workqueue Alice Ryhl
2023-05-19 0:17 ` Martin Rodriguez Reboredo
2023-05-23 11:07 ` Alice Ryhl
2023-05-30 7:19 ` Andreas Hindborg
2023-05-30 13:23 ` Martin Rodriguez Reboredo
2023-05-30 14:13 ` Miguel Ojeda
2023-05-24 14:51 ` Benno Lossin
2023-05-31 9:07 ` Alice Ryhl
2023-05-30 8:51 ` Andreas Hindborg
2023-05-31 14:07 ` Alice Ryhl
2023-05-17 20:31 ` [PATCH v1 7/7] rust: workqueue: add `try_spawn` helper method Alice Ryhl
2023-05-19 0:22 ` Martin Rodriguez Reboredo
2023-05-24 14:52 ` Benno Lossin
2023-05-31 14:03 ` Alice Ryhl
2023-05-17 21:48 ` [PATCH v1 0/7] Bindings for the workqueue Tejun Heo
2023-05-17 22:22 ` Alice Ryhl
2023-05-23 14:08 ` Andreas Hindborg [this message]
2023-05-23 14:14 ` Andreas Hindborg
2023-05-24 12:33 ` Alice Ryhl
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