Commit 47f0dbe8 authored by Alice Ryhl's avatar Alice Ryhl Committed by Tejun Heo
Browse files

rust: workqueue: implement `WorkItemPointer` for pointer types 



This implements the `WorkItemPointer` trait for the pointer types that
you are likely to use the workqueue with. The `Arc` type is for
reference counted objects, and the `Pin<Box<T>>` type is for objects
where the caller has exclusive ownership of the object.

Co-developed-by: default avatarGary Guo <gary@garyguo.net>
Signed-off-by: default avatarGary Guo <gary@garyguo.net>
Signed-off-by: default avatarAlice Ryhl <aliceryhl@google.com>
Reviewed-by: default avatarMartin Rodriguez Reboredo <yakoyoku@gmail.com>
Reviewed-by: default avatar"Andreas Hindborg (Samsung)" <nmi@metaspace.dk>
Reviewed-by: default avatarBenno Lossin <benno.lossin@proton.me>
Reviewed-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 7324b889

rust/kernel/workqueue.rs

+96 −1
Original line number Diff line number Diff line
@@ -28,8 +28,10 @@ 
//!

//! C header: [`include/linux/workqueue.h`](../../../../include/linux/workqueue.h)



use crate::{bindings, prelude::*, sync::LockClassKey, types::Opaque};

use crate::{bindings, prelude::*, sync::Arc, sync::LockClassKey, types::Opaque};

use alloc::boxed::Box;

use core::marker::PhantomData;

use core::pin::Pin;



/// Creates a [`Work`] initialiser with the given name and a newly-created lock class.

#[macro_export]
@@ -363,6 +365,99 @@ unsafe fn raw_get_work(ptr: *mut Self) -> *mut $crate::workqueue::Work<$work_typ 
    )*};

}



unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Arc<T>

where

    T: WorkItem<ID, Pointer = Self>,

    T: HasWork<T, ID>,

{

    unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {

        // SAFETY: The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.

        let ptr = ptr as *mut Work<T, ID>;

        // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.

        let ptr = unsafe { T::work_container_of(ptr) };

        // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.

        let arc = unsafe { Arc::from_raw(ptr) };



        T::run(arc)

    }

}



unsafe impl<T, const ID: u64> RawWorkItem<ID> for Arc<T>

where

    T: WorkItem<ID, Pointer = Self>,

    T: HasWork<T, ID>,

{

    type EnqueueOutput = Result<(), Self>;



    unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput

    where

        F: FnOnce(*mut bindings::work_struct) -> bool,

    {

        // Casting between const and mut is not a problem as long as the pointer is a raw pointer.

        let ptr = Arc::into_raw(self).cast_mut();



        // SAFETY: Pointers into an `Arc` point at a valid value.

        let work_ptr = unsafe { T::raw_get_work(ptr) };

        // SAFETY: `raw_get_work` returns a pointer to a valid value.

        let work_ptr = unsafe { Work::raw_get(work_ptr) };



        if queue_work_on(work_ptr) {

            Ok(())

        } else {

            // SAFETY: The work queue has not taken ownership of the pointer.

            Err(unsafe { Arc::from_raw(ptr) })

        }

    }

}



unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Pin<Box<T>>

where

    T: WorkItem<ID, Pointer = Self>,

    T: HasWork<T, ID>,

{

    unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {

        // SAFETY: The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.

        let ptr = ptr as *mut Work<T, ID>;

        // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.

        let ptr = unsafe { T::work_container_of(ptr) };

        // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.

        let boxed = unsafe { Box::from_raw(ptr) };

        // SAFETY: The box was already pinned when it was enqueued.

        let pinned = unsafe { Pin::new_unchecked(boxed) };



        T::run(pinned)

    }

}



unsafe impl<T, const ID: u64> RawWorkItem<ID> for Pin<Box<T>>

where

    T: WorkItem<ID, Pointer = Self>,

    T: HasWork<T, ID>,

{

    type EnqueueOutput = ();



    unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput

    where

        F: FnOnce(*mut bindings::work_struct) -> bool,

    {

        // SAFETY: We're not going to move `self` or any of its fields, so its okay to temporarily

        // remove the `Pin` wrapper.

        let boxed = unsafe { Pin::into_inner_unchecked(self) };

        let ptr = Box::into_raw(boxed);



        // SAFETY: Pointers into a `Box` point at a valid value.

        let work_ptr = unsafe { T::raw_get_work(ptr) };

        // SAFETY: `raw_get_work` returns a pointer to a valid value.

        let work_ptr = unsafe { Work::raw_get(work_ptr) };



        if !queue_work_on(work_ptr) {

            // SAFETY: This method requires exclusive ownership of the box, so it cannot be in a

            // workqueue.

            unsafe { ::core::hint::unreachable_unchecked() }

        }

    }

}



/// Returns the system work queue (`system_wq`).

///

/// It is the one used by `schedule[_delayed]_work[_on]()`. Multi-CPU multi-threaded. There are