Messages in this thread | | | Date | Thu, 25 May 2023 13:46:40 +0000 | From | Benno Lossin <> | Subject | Re: [PATCH v2 4/4] rust: task: add `Send` marker to `Task` |
| |
On 5/23/23 16:44, Alice Ryhl wrote: > When a type also implements `Sync`, the meaning of `Send` is just "this > type may be accessed mutably from threads other than the one it is > created on". That's ok for this type. > > Signed-off-by: Alice Ryhl <aliceryhl@google.com> > Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
> --- > rust/kernel/task.rs | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs > index 526d29a0ae27..7eda15e5f1b3 100644 > --- a/rust/kernel/task.rs > +++ b/rust/kernel/task.rs > @@ -64,8 +64,14 @@ macro_rules! current { > #[repr(transparent)] > pub struct Task(pub(crate) Opaque<bindings::task_struct>); > > -// SAFETY: It's OK to access `Task` through references from other threads because we're either > -// accessing properties that don't change (e.g., `pid`, `group_leader`) or that are properly > +// SAFETY: By design, the only way to access a `Task` is via the `current` function or via an > +// `ARef<Task>` obtained through the `AlwaysRefCounted` impl. This means that the only situation in > +// which a `Task` can be accessed mutably is when the refcount drops to zero and the destructor > +// runs. It is safe for that to happen on any thread, so it is ok for this type to be `Send`. > +unsafe impl Send for Task {} > + > +// SAFETY: It's OK to access `Task` through shared references from other threads because we're > +// either accessing properties that don't change (e.g., `pid`, `group_leader`) or that are properly > // synchronised by C code (e.g., `signal_pending`). > unsafe impl Sync for Task {} > > -- > 2.40.1.698.g37aff9b760-goog >
-- Cheers, Benno
| |