Messages in this thread Patch in this message | | | Date | Thu, 1 Jun 2023 13:49:44 +0000 | Subject | [PATCH v2 6/8] rust: workqueue: implement `WorkItemPointer` for pointer types | From | Alice Ryhl <> |
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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: Gary Guo <gary@garyguo.net> Signed-off-by: Gary Guo <gary@garyguo.net> Signed-off-by: Alice Ryhl <aliceryhl@google.com> --- rust/kernel/workqueue.rs | 97 +++++++++++++++++++++++++++++++++++++++- 1 file changed, 96 insertions(+), 1 deletion(-)
diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs index dbf0aab29a85..f06a2f036d8b 100644 --- a/rust/kernel/workqueue.rs +++ b/rust/kernel/workqueue.rs @@ -28,8 +28,10 @@ //! //! C header: [`include/linux/workqueue.h`](../../../../include/linux/workqueue.h) -use crate::{bindings, prelude::*, types::Opaque}; +use crate::{bindings, prelude::*, sync::Arc, types::Opaque}; +use alloc::boxed::Box; use core::marker::{PhantomData, PhantomPinned}; +use core::pin::Pin; /// A kernel work queue. /// @@ -323,6 +325,99 @@ 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) as *mut T; + + // 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 -- 2.41.0.rc0.172.g3f132b7071-goog
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