linux-kernel - Re: [PATCH v2 1/3] rust_binder: freeze_notif

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Message-ID: <CAH5fLgiChj29SbwN-5vHhCNzaUa7wewOXe1D8mN3XFfyZr33gw@mail.gmail.com>
Date: Wed, 8 Oct 2025 18:34:54 +0200
From: Alice Ryhl <aliceryhl@...gle.com>
To: Carlos Llamas <cmllamas@...gle.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Arve Hjønnevåg <arve@...roid.com>, 
	Todd Kjos <tkjos@...roid.com>, Martijn Coenen <maco@...roid.com>, 
	Joel Fernandes <joelagnelf@...dia.com>, Christian Brauner <brauner@...nel.org>, 
	Suren Baghdasaryan <surenb@...gle.com>, linux-kernel@...r.kernel.org, 
	rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v2 1/3] rust_binder: freeze_notif_done should resend if
 wrong state

On Wed, Oct 8, 2025 at 6:32 PM Carlos Llamas <cmllamas@...gle.com> wrote:
>
> On Tue, Oct 07, 2025 at 09:39:51AM +0000, Alice Ryhl wrote:
> > Consider the following scenario:
> > 1. A freeze notification is delivered to thread 1.
> > 2. The process becomes frozen or unfrozen.
> > 3. The message for step 2 is delivered to thread 2 and ignored because
> >    there is already a pending notification from step 1.
> > 4. Thread 1 acknowledges the notification from step 1.
> > In this case, step 4 should ensure that the message ignored in step 3 is
> > resent as it can now be delivered.
>
> hmmm, I wonder what happens with 3 threads involved where the state goes
> back to the (unconsumed) initial freeze notification. Userspace will
> probably see two separate notifications of the same state?

The way I implemented it, the work items report the current state when
the work item is *executed*, and they do nothing if there's no change
since last notification.

Alice