Hi,

On 1/27/21 11:01 PM, Pavel Machek wrote:

Hi!

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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 ?

Is it a regression? AFAIK it is a bug that has been there
forever... My original plan was to simply wait for 5.12, so it gets
full release of testing...

It may have been a pre-existing bug which got triggered by libata changes?

I don't know. I almost always run all my locally build kernels with lockdep
enabled and as the maintainer of the vboxvideo, vboxguest and vboxsf guest
drivers in the mainline kernel I quite often boot local build kernels inside
a vm.

So I believe that lockdep tripping over this is new in 5.11, which is why
I called it a regression.

And the fix seems very safe and simple, so IMHO it would be good to get
this into 5.11

Regards,

Hans