Alice Ryhl ac681835b6 rust: file: add abstraction for poll_table ... The existing `CondVar` abstraction is a wrapper around `wait_queue_head`, but it does not support all use-cases of the C `wait_queue_head` type. To be specific, a `CondVar` cannot be registered with a `struct poll_table`. This limitation has the advantage that you do not need to call `synchronize_rcu` when destroying a `CondVar`. However, we need the ability to register a `poll_table` with a `wait_queue_head` in Rust Binder. To enable this, introduce a type called `PollCondVar`, which is like `CondVar` except that you can register a `poll_table`. We also introduce `PollTable`, which is a safe wrapper around `poll_table` that is intended to be used with `PollCondVar`. The destructor of `PollCondVar` unconditionally calls `synchronize_rcu` to ensure that the removal of epoll waiters has fully completed before the `wait_queue_head` is destroyed. That said, `synchronize_rcu` is rather expensive and is not needed in all cases: If we have never registered a `poll_table` with the `wait_queue_head`, then we don't need to call `synchronize_rcu`. (And this is a common case in Binder - not all processes use Binder with epoll.) The current implementation does not account for this, but if we find that it is necessary to improve this, a future patch could store a boolean next to the `wait_queue_head` to keep track of whether a `poll_table` has ever been registered. Reviewed-by: Benno Lossin <benno.lossin@proton.me> Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com> Reviewed-by: Trevor Gross <tmgross@umich.edu> Signed-off-by: Alice Ryhl <aliceryhl@google.com> Link: https://lore.kernel.org/r/20240915-alice-file-v10-8-88484f7a3dcf@google.com Signed-off-by: Christian Brauner <brauner@kernel.org>		2024-09-30 13:02:29 +02:00
..
bindings	rust: file: add abstraction for poll_table	2024-09-30 13:02:29 +02:00
helpers	rust: file: add Kuid wrapper	2024-09-30 13:02:29 +02:00
kernel	rust: file: add abstraction for poll_table	2024-09-30 13:02:29 +02:00
macros	kbuild: rust: replace proc macros dependency on core.o with the version text	2024-09-05 22:44:51 +02:00
uapi	rust: allow dead_code for never constructed bindings	2024-07-10 10:28:51 +02:00
.gitignore	rust: support running Rust documentation tests as KUnit ones	2023-07-19 09:32:53 -06:00
bindgen_parameters	rust: Ignore preserve-most functions	2023-12-13 01:09:55 +01:00
build_error.rs	rust: add build_error crate	2022-12-04 01:59:16 +01:00
compiler_builtins.rs	rust: add intrinsics to fix -Os builds	2024-08-10 00:05:10 +02:00
exports.c	rust: kbuild: auto generate helper exports	2024-08-19 11:09:02 +02:00
Makefile	kbuild: rust: replace proc macros dependency on core.o with the version text	2024-09-05 22:44:51 +02:00