linux-kernel - Re: 5.11 new lockdep warning related to led-class code (also may involve ata / piix controller)

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Date:   Mon, 25 Jan 2021 14:15:34 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Jens Axboe <axboe@...nel.dk>, Dan Murphy <dmurphy@...com>,
        linux-ide@...r.kernel.org, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: 5.11 new lockdep warning related to led-class code (also may
 involve ata / piix controller)

Hi,

On 1/13/21 9:59 AM, Hans de Goede wrote:
> Hi,
> 
> On 1/12/21 11:30 PM, Pavel Machek wrote:
>> Hi!
>>
>>> Booting a 5.11-rc2 kernel with lockdep enabled inside a virtualbox vm (which still
>>> emulates good old piix ATA controllers) I get the below lockdep splat early on during boot:
>>>
>>> This seems to be led-class related but also seems to have a (P)ATA
>>> part to it. To the best of my knowledge this is a new problem in
>>> 5.11 .
>>
>> This is on my for-next branch:
>>
>> commit 9a5ad5c5b2d25508996f10ee6b428d5df91d9160 (HEAD -> for-next, origin/for-next)
>>
>>     leds: trigger: fix potential deadlock with libata
>>     
>>     We have the following potential deadlock condition:
>>     
>>      ========================================================
>>      WARNING: possible irq lock inversion dependency detected
>>      5.10.0-rc2+ #25 Not tainted
>>      --------------------------------------------------------
>>      swapper/3/0 just changed the state of lock:
>>      ffff8880063bd618 (&host->lock){-...}-{2:2}, at: ata_bmdma_interrupt+0x27/0x200
>>      but this lock took another, HARDIRQ-READ-unsafe lock in the past:
>>       (&trig->leddev_list_lock){.+.?}-{2:2}
>>
>> If I'm not mistaken, that should fix your issue.
> 
> I can confirm that this fixes things, thanks.
> 
> I assume that this will be part of some future 5.11 fixes pull-req?

This *regression* fix seems to still have not landed in 5.11-rc5, can
we please get this on its way to Linus ?

Regards,

Hans