linux-kernel - Re: [PATCH] driver core: fix async device shutdown hang

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Message-ID: <751d4ba8-1e35-47a5-9a94-9873ff2619ae@gmail.com>
Date: Tue, 17 Sep 2024 19:20:41 -0500
From: stuart hayes <stuart.w.hayes@...il.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-kernel@...r.kernel.org, "Rafael J . Wysocki" <rafael@...nel.org>,
 Martin Belanger <Martin.Belanger@...l.com>,
 Oliver O'Halloran <oohall@...il.com>, Daniel Wagner <dwagner@...e.de>,
 Keith Busch <kbusch@...nel.org>, Lukas Wunner <lukas@...ner.de>,
 David Jeffery <djeffery@...hat.com>, Jeremy Allison <jallison@....com>,
 Jens Axboe <axboe@...com>, Christoph Hellwig <hch@....de>,
 Sagi Grimberg <sagi@...mberg.me>, linux-nvme@...ts.infradead.org,
 Nathan Chancellor <nathan@...nel.org>, Jan Kiszka <jan.kiszka@...mens.com>
Subject: Re: [PATCH] driver core: fix async device shutdown hang

On 9/17/2024 3:42 PM, Greg Kroah-Hartman wrote:
> On Tue, Sep 17, 2024 at 03:15:17PM -0500, Stuart Hayes wrote:
>> Modify device_shutdown() so that supplier devices do not wait for
>> consumer devices to be shut down first when the devlink is sync state
>> only, since the consumer is not dependent on the supplier in this case.
>>
>> Without this change, a circular dependency could hang the system.
>>
>> Signed-off-by: Stuart Hayes <stuart.w.hayes@...il.com>
> 
> What commit id does this fix?  Should it go to stable?
> 
> And what driver is causing this problem, is this a regression or for
> something new that just got added to the tree?
> 
> thanks,
> 
> greg k-h

This fixes commit 8064952c65045f05ee2671fe437770e50c151776, in
driver-core-next & linux-next... it's problem with code that was just
added to the tree (in drivers/base/core.c).  It is not in stable.

Apologies, I should have mentioned that from the start.

The issue was found using qemu... a pl061 device (supplier) and
gpio-keys device (consumer), from a qemu-generated device tree with
the aarch64 architecture.  I don't know why the devlink is in the
sync_state_only state in this case.  I didn't dig into that, because
I figured the shutdown code shouldn't hang regardless.