linux-kernel - Re: [PATCH v3 1/4] rust: sync: add `CondVar::notify

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ZZb_b-6f9Ib1NdOt@boqun-archlinux>
Date: Thu, 4 Jan 2024 10:56:47 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
	Wedson Almeida Filho <wedsonaf@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...sung.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
	Waiman Long <longman@...hat.com>, Tiago Lam <tiagolam@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Martin Rodriguez Reboredo <yakoyoku@...il.com>,
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/4] rust: sync: add `CondVar::notify_sync`

On Thu, Jan 04, 2024 at 02:02:41PM +0000, Alice Ryhl wrote:
> Wake up another thread synchronously.
> 
> This method behaves like `notify_one`, except that it hints to the
> scheduler that the current thread is about to go to sleep, so it should
> schedule the target thread on the same CPU.
> 
> This is used by Rust Binder as a performance optimization. When sending
> a transaction to a different process, we usually know which thread will
> handle it, so we can schedule that thread for execution next on this
> CPU for better cache locality.
> 
> Reviewed-by: Benno Lossin <benno.lossin@...ton.me>
> Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@...il.com>
> Reviewed-by: Tiago Lam <tiagolam@...il.com>
> Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
> ---
>  rust/kernel/sync/condvar.rs | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/rust/kernel/sync/condvar.rs b/rust/kernel/sync/condvar.rs
> index f65e19d5a37c..1a3f7b8e03dc 100644
> --- a/rust/kernel/sync/condvar.rs
> +++ b/rust/kernel/sync/condvar.rs
> @@ -155,6 +155,12 @@ fn notify(&self, count: i32, flags: u32) {
>          };
>      }
>  
> +    /// Calls the kernel function to notify one thread synchronously.

I feel like "synchronously" needs some explanation here (e.g. using the
same description in the commit log), but let's see if other future users
really need this ;-)

Reviewed-by: Boqun Feng <boqun.feng@...il.com>

Regards,
Boqun

> +    pub fn notify_sync(&self) {
> +        // SAFETY: `wait_list` points to valid memory.
> +        unsafe { bindings::__wake_up_sync(self.wait_list.get(), bindings::TASK_NORMAL) };
> +    }
> +
>      /// Wakes a single waiter up, if any.
>      ///
>      /// This is not 'sticky' in the sense that if no thread is waiting, the notification is lost
> 
> -- 
> 2.43.0.472.g3155946c3a-goog
>