Re: [PATCH v2 4/4] rust: sync: update integer types in CondVar

Martin Rodriguez Reboredo
2023-12-16T16:42:55Z

On 12/16/23 12:31, Alice Ryhl wrote:
> Reduce the chances of compilation failures due to integer type
> mismatches in `CondVar`.
>
> When an integer is defined using a #define in C, bindgen doesn't know
> which integer type it is supposed to be, so it will just use `u32` by
> default (if it fits in an u32). Whenever the right type is something
> else, we insert a cast in Rust. However, this means that the code has a
> lot of extra casts, and sometimes the code will be missing casts if u32
> happens to be correct on the developer's machine, even though the type
> might be something else on a different platform.
>
> This patch updates all uses of such constants in
> `rust/kernel/sync/condvar.rs` to use constants defined with the right
> type. This allows us to remove various unnecessary casts, while also
> future-proofing for the case where `unsigned int != u32`.
>
> I wrote this patch at the suggestion of Benno in [1].
>
> Link: https://lore.kernel.org/all/nAEg-6vbtX72ZY3oirDhrSEf06TBWmMiTt73EklMzEAzN4FD4mF3TPEyAOxBZgZtjzoiaBYtYr3s8sa9wp1uYH9vEWRf2M-Lf4I0BY9rAgk=@proton.me/ [1]
> Suggested-by: Benno Lossin <benno.lossin@proton.me>
> Signed-off-by: Alice Ryhl <aliceryhl@google.com>
> ---
> [...]
> @@ -174,22 +178,15 @@ pub fn wait_interruptible_timeout<T: ?Sized, B: Backend>(
> }
>
> /// Calls the kernel function to notify the appropriate number of threads with the given flags.

There are no more flags, please update the comment.

> - fn notify(&self, count: i32, flags: u32) {
> + fn notify(&self, count: c_int) {
> // SAFETY: `wait_list` points to valid memory.
> - unsafe {
> - bindings::__wake_up(
> - self.wait_list.get(),
> - bindings::TASK_NORMAL,
> - count,
> - flags as _,
> - )
> - };
> + unsafe { bindings::__wake_up(self.wait_list.get(), TASK_NORMAL, count, ptr::null_mut()) };
> }
> …