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Date: Fri, 15 May 2026 08:28:29 +0000
From: Tzung-Bi Shih <tzungbi@kernel.org>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Bartosz Golaszewski <brgl@kernel.org>,
	Linus Walleij <linusw@kernel.org>,
	Benson Leung <bleung@chromium.org>, linux-kernel@vger.kernel.org,
	chrome-platform@lists.linux.dev, driver-core@lists.linux.dev,
	linux-doc@vger.kernel.org, linux-gpio@vger.kernel.org,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Danilo Krummrich <dakr@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>,
	Johan Hovold <johan@kernel.org>,
	"Paul E . McKenney" <paulmck@kernel.org>
Subject: Re: [PATCH v10 8/9] platform/chrome: Protect cros_ec_device
 lifecycle with revocable
Message-ID: <agbZLY0wn85JqTFV@google.com>
References: <20260508105448.31799-1-tzungbi@kernel.org>
 <20260508105448.31799-9-tzungbi@kernel.org>
 <20260508115309.GA9254@nvidia.com>
 <agVCoxuTu7l60TH-@google.com>
 <20260514160214.GH787748@nvidia.com>
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In-Reply-To: <20260514160214.GH787748@nvidia.com>

On Thu, May 14, 2026 at 01:02:14PM -0300, Jason Gunthorpe wrote:
> On Thu, May 14, 2026 at 03:33:55AM +0000, Tzung-Bi Shih wrote:
> 
> > > Given you say this is such a bug I think you really should be sending
> > > a series that is patches 5 through 7 from the other series and a
> > > simple rwsem instead of misc_deregister_sync() to deal with this bug
> > > ASAP. No need to complicate a simple bug fix in a driver with all
> > > these core changes.
> > 
> > Apologies for missing this suggestion.
> > 
> > For "patches 5 through 7 from the other series" I guess you're referring:
> > - https://lore.kernel.org/all/20260427134659.95181-6-tzungbi@kernel.org
> > - https://lore.kernel.org/all/20260427134659.95181-7-tzungbi@kernel.org
> > - https://lore.kernel.org/all/20260427134659.95181-8-tzungbi@kernel.org
> 
> Yes
> 
> > Could you provide a bit more detail on the rwsem approach?  I'm not
> > entirely clear on what data or operations the rwsem would be protecting.
> 
> Just put a rwsem, or even scru, inside the driver's fops.
> 
> You can refactor that out to a misc or revocable later.

I see.  Thank you for your suggestion.  I will explore it and send out a
new version.