From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b="J+HzaMOm" Received: from madras.collabora.co.uk (madras.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e5ab]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 98F53121; Thu, 7 Dec 2023 08:00:50 -0800 (PST) Received: from [10.3.2.161] (zone.collabora.co.uk [167.235.23.81]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: dmitry.osipenko) by madras.collabora.co.uk (Postfix) with ESMTPSA id BE36A660739F; Thu, 7 Dec 2023 16:00:47 +0000 (GMT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1701964848; bh=o60ZivJAjuNVk9lMONJuI83P129Uc3ICsB0e+skvORE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=J+HzaMOmkobFxYMAtj8seSUoTES01PM+gUy6AJ1Rby/oRd0J7+PDOezsV5mD/tn6K EkSmnkdqoJuT8pb2R0q7hAurSYtX9c9b2lEnTDBPrmyJ/TIrJppmb14MZFbw8y86I3 FqvfijCWVaKSW5bq6BY73mzVmS6dSpfajFksSpBuz1tD8SlmOMXZ7zYvChz2eZ+FD/ NKR9hvbaqcvGJHK2sB9UhMf5OUH9dBlNMribUGYAOrOZ3fqexBu7YRmg4XGYHuJH1h 71YB2AJZxJOwZKdvEGbB7jC0hPO+HAoOew1HOrDkHkjJlB9iER4S6RVUXfxJ/7FuB9 3wlZgxaWA9ALg== Message-ID: <95cc7716-ba01-e239-e7c0-eba0b7da7955@collabora.com> Date: Thu, 7 Dec 2023 19:00:42 +0300 Precedence: bulk X-Mailing-List: linux-i2c@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH v2] i2c: rk3x: fix potential spinlock recursion on poll Content-Language: en-US To: Dragan Simic , Jensen Huang Cc: Heiko Stuebner , Andi Shyti , linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Morgan , Benjamin Bara References: <20231207082200.16388-1-jensenhuang@friendlyarm.com> <5e11553952c02ad20591992be4284bbd@manjaro.org> From: Dmitry Osipenko In-Reply-To: <5e11553952c02ad20591992be4284bbd@manjaro.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 12/7/23 17:10, Dragan Simic wrote: > On 2023-12-07 10:25, Jensen Huang wrote: >> On Thu, Dec 7, 2023 at 4:37 PM Dragan Simic wrote: >>> >>> On 2023-12-07 09:21, Jensen Huang wrote: >>> > Possible deadlock scenario (on reboot): >>> > rk3x_i2c_xfer_common(polling) >>> >     -> rk3x_i2c_wait_xfer_poll() >>> >         -> rk3x_i2c_irq(0, i2c); >>> >             --> spin_lock(&i2c->lock); >>> >             ... >>> >         >>> >         -> rk3x_i2c_irq(0, i2c); >>> >             --> spin_lock(&i2c->lock); (deadlock here) >>> > >>> > Store the IRQ number and disable/enable it around the polling >>> transfer. >>> > This patch has been tested on NanoPC-T4. >>> >>> In case you haven't already seen the related discussion linked below, >>> please have a look.  I also added more people to the list of recipients, >>> in an attempt to make everyone aware of the different approaches to >>> solving this issue. >>> >>> https://lore.kernel.org/all/655177f4.050a0220.d85c9.3ba0@mx.google.com/T/#m6fc9c214452fec6681843e7f455978c35c6f6c8b >> >> Thank you for providing the information. I hadn't seen this link before. >> After carefully looking into the related discussion, it appears that >> Dmitry Osipenko is already working on a suitable patch. To avoid >> duplication >> or conflicts, my patch can be discarded. > > Thank you for responding so quickly.  Perhaps it would be best to hear > from Dmitry as well, before discarding anything.  It's been a while > since Dmitry wrote about working on the patch, so he might have > abandoned it. This patch is okay. In general, will be better to have IRQ disabled by default like I did in my variant, it should allow to remove the spinlock entirely. Of course this also can be done later on in a follow up patches. Jensen, feel free to use my variant of the patch, add my s-o-b+co-developed tags to the commit msg if you'll do. Otherwise I'll be able to send my patch next week. -- Best regards, Dmitry