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Date:   Wed, 17 May 2023 09:59:05 +0000
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Subject: [PATCH v1 2/2] rust: task: add `Send` marker to `Task`
From:   Alice Ryhl <aliceryhl@google.com>
To:     Miguel Ojeda <ojeda@kernel.org>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Alex Gaynor <alex.gaynor@gmail.com>
Cc:     Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        "=?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?=" <bjorn3_gh@protonmail.com>,
        Benno Lossin <benno.lossin@proton.me>,
        Alice Ryhl <aliceryhl@google.com>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
        patches@lists.linux.dev
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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>
---
 rust/kernel/task.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs
index 526d29a0ae27..4f1fe9aa9f6e 100644
--- a/rust/kernel/task.rs
+++ b/rust/kernel/task.rs
@@ -64,6 +64,11 @@ macro_rules! current {
 #[repr(transparent)]
 pub struct Task(pub(crate) Opaque<bindings::task_struct>);
 
+// SAFETY: The only situation in which this 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 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`).
-- 
2.40.1.606.ga4b1b128d6-goog