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Date: Mon, 26 Jan 2026 23:36:12 +0100
Message-Id: <DFYVOX2J1WKG.2GJKZ0T6O21NP@kernel.org>
Cc: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>, "Johan Hovold"
 <johan@kernel.org>, "Rafael J . Wysocki" <rafael@kernel.org>, "Tzung-Bi
 Shih" <tzungbi@kernel.org>, "Bartosz Golaszewski"
 <bartosz.golaszewski@oss.qualcomm.com>, "Linus Walleij"
 <linusw@kernel.org>, "Jonathan Corbet" <corbet@lwn.net>, "Shuah Khan"
 <shuah@kernel.org>, "Laurent Pinchart" <laurent.pinchart@ideasonboard.com>,
 "Wolfram Sang" <wsa+renesas@sang-engineering.com>, "Simona Vetter"
 <simona.vetter@ffwll.ch>, "Dan Williams" <dan.j.williams@intel.com>,
 <linux-doc@vger.kernel.org>, <linux-kselftest@vger.kernel.org>,
 <linux-kernel@vger.kernel.org>
To: "Jason Gunthorpe" <jgg@nvidia.com>
From: "Danilo Krummrich" <dakr@kernel.org>
Subject: Re: [PATCH 0/3] Revert "revocable: Revocable resource management"
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References: <20260124170535.11756-1-johan@kernel.org>
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 <2026012554-chatty-policy-42a1@gregkh>
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 <20260126170720.GN1134360@nvidia.com>
In-Reply-To: <20260126170720.GN1134360@nvidia.com>

On Mon Jan 26, 2026 at 6:07 PM CET, Jason Gunthorpe wrote:
> On Mon, Jan 26, 2026 at 05:08:20PM +0100, Danilo Krummrich wrote:
>> Yes, the majority of uses is access(), not try_access(); not sure if rws=
em is
>> the better solution though.
>
> rwsem is much faster on destroy and somewhat slower on read. Which
> sounds to match the use case here. Ie you wouldn't need to do special
> effort to bundle the synchronize_srcu()

While not that many, the try_access() cases may still be in hot paths, wher=
eas
the destroy case is always in a cold path, i.e. device driver unbind. Also =
note
that if the resource is released "manually" before driver unbind, we use
revoke_nosync() as the destructor already guarantees that there are no more
users.