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Date: Fri, 06 Feb 2026 11:23:09 +0100
Message-Id: <DG7SZND1GWR4.3C5NLKY4SYC0M@kernel.org>
From: "Danilo Krummrich" <dakr@kernel.org>
Subject: Re: [RFC PATCH 2/4] rust: sync: Add dma_fence abstractions
Cc: "Philipp Stanner" <phasta@kernel.org>, "David Airlie"
 <airlied@gmail.com>, "Simona Vetter" <simona@ffwll.ch>, "Alice Ryhl"
 <aliceryhl@google.com>, "Gary Guo" <gary@garyguo.net>, "Benno Lossin"
 <lossin@kernel.org>, =?utf-8?q?Christian_K=C3=B6nig?=
 <christian.koenig@amd.com>, "Daniel Almeida"
 <daniel.almeida@collabora.com>, "Joel Fernandes" <joelagnelf@nvidia.com>,
 <linux-kernel@vger.kernel.org>, <dri-devel@lists.freedesktop.org>,
 <rust-for-linux@vger.kernel.org>
To: "Boris Brezillon" <boris.brezillon@collabora.com>
References: <20260203081403.68733-2-phasta@kernel.org>
 <20260203081403.68733-4-phasta@kernel.org> <20260205095727.4c3e2941@fedora>
In-Reply-To: <20260205095727.4c3e2941@fedora>

On Thu Feb 5, 2026 at 9:57 AM CET, Boris Brezillon wrote:
> On Tue,  3 Feb 2026 09:14:01 +0100
> Philipp Stanner <phasta@kernel.org> wrote:
> Unfortunately, I don't know how to translate that in rust, but we
> need a way to check if any path code path does a DmaFence.signal(),
> go back to the entry point (for a WorkItem, that would be
> WorkItem::run() for instance), and make it a DmaFenceSignallingPath.
> Not only that, but we need to know all the deps that make it so
> this path can be called (if I take the WorkItem example, that would
> be the path that leads to the WorkItem being scheduled).

I think we need a guard object for this that is not Send, just like for any
other lock.

Internally, those markers rely on lockdep, i.e. they just acquire and relea=
se a
"fake" lock.