linux-kernel - Re: [PATCH 3/4] gpu: nova-core: gsp: fix improper handling of empty slot in cmdq

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Message-ID: <ee459198-04f2-4bae-8e1f-4ec413d92f89@nvidia.com>
Date: Wed, 21 Jan 2026 19:26:16 -0800
From: John Hubbard <jhubbard@...dia.com>
To: Eliot Courtney <ecourtney@...dia.com>, Danilo Krummrich
 <dakr@...nel.org>, Alexandre Courbot <acourbot@...dia.com>,
 Alice Ryhl <aliceryhl@...gle.com>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Alistair Popple <apopple@...dia.com>
Cc: nouveau@...ts.freedesktop.org, rust-for-linux@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] gpu: nova-core: gsp: fix improper handling of empty
 slot in cmdq

On 1/21/26 6:59 PM, Eliot Courtney wrote:
> +            // The area is contiguous and we leave an empty slot before `rx`.
> +            // PANIC: since `rx > tx` we have `rx - tx - 1 >= 0`
> +            // PANIC: since `tx < rx < MSGQ_NUM_PAGES && after_tx.len() == MSGQ_NUM_PAGES - tx`:
> +            //   `rx - 1 <= MSGQ_NUM_PAGES` -> `rx - tx - 1 <= MSGQ_NUM_PAGES - tx`
> +            //   -> `rx - tx - 1 <= after_tx.len()`

Hi Eliot,

Documentation nit: the proofs are great, but the above just does
not go into my head easily, because it's a proof, rather than a
sentence.

Can you please reword these PANIC comments so that they are complete
sentences, along the lines of:

    // PANIC: a > b and therefore c cannot overflow, therefore this
    // cannot panic.

And please also use words "and", "therefore", "because", instead of 
symbols such as "&&".

Same for the other patch with PANIC comments.

I did a quick search in Rust for Linux, before writing this, in order to
ensure that what I'm recommending is How It Is Done. (Not to claim that
Nova in particular is fully correct, though.)

thanks,
-- 
John Hubbard