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Date: Thu, 07 Dec 2023 15:10:29 +0100
From: Dragan Simic <dsimic@manjaro.org>
To: Jensen Huang <jensenhuang@friendlyarm.com>
Cc: Heiko Stuebner <heiko@sntech.de>, Andi Shyti <andi.shyti@kernel.org>,
 linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org,
 linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, Dmitry Osipenko
 <dmitry.osipenko@collabora.com>, Chris Morgan <macroalpha82@gmail.com>,
 Benjamin Bara <bbara93@gmail.com>
Subject: Re: [PATCH v2] i2c: rk3x: fix potential spinlock recursion on poll
In-Reply-To: <CAMpZ1qHUnTDQ78gdrQF9Sx_-XfLM-B+H-0bL1-+twKsno+JOvg@mail.gmail.com>
References: <20231207082200.16388-1-jensenhuang@friendlyarm.com>
 <ebf6cf8ec3b5befd673d295061fa2738@manjaro.org>
 <CAMpZ1qHUnTDQ78gdrQF9Sx_-XfLM-B+H-0bL1-+twKsno+JOvg@mail.gmail.com>
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On 2023-12-07 10:25, Jensen Huang wrote:
> On Thu, Dec 7, 2023 at 4:37 PM Dragan Simic <dsimic@manjaro.org> 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 interrupt>
>> >         -> 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.