On Sun, 15 Sep 2024 14:41:28 +0000 Alice Ryhl aliceryhl@google.com wrote:
The `LockedBy::access` method only requires a shared reference to the owner, so if we have shared access to the `LockedBy` from several threads at once, then two threads could call `access` in parallel and both obtain a shared reference to the inner value. Thus, require that `T: Sync` when calling the `access` method.
An alternative is to require `T: Sync` in the `impl Sync for LockedBy`. This patch does not choose that approach as it gives up the ability to use `LockedBy` with `!Sync` types, which is okay as long as you only use `access_mut`.
Cc: stable@vger.kernel.org Fixes: 7b1f55e3a984 ("rust: sync: introduce `LockedBy`") Signed-off-by: Alice Ryhl aliceryhl@google.com
Reviewed-by: Gary Guo gary@garyguo.net
You probably also want to have a Suggested-by to credit Boqun for suggesting the current implementation.
Best, Gary
Changes in v2:
- Use a `where T: Sync` on `access` instead of changing `impl Sync for LockedBy`.
- Link to v1: https://lore.kernel.org/r/20240912-locked-by-sync-fix-v1-1-26433cbccbd2@goog...
rust/kernel/sync/locked_by.rs | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-)