linux-kernel - Re: [BUG][v6.9-rc6] Deadlock with: Revert "drm/qxl: simplify qxl_fence

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Message-ID: <e26ba70d-340a-43bf-8e39-7214e76ab141@gmail.com>
Date: Wed, 8 May 2024 14:42:38 +0200
From: Anders Blomdell <anders.blomdell@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>, David Airlie <airlied@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
 Maxime Ripard <mripard@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
 Alex Constantino <dreaming.about.electric.sheep@...il.com>,
 Timo Lindfors <timo.lindfors@....fi>, Gerd Hoffmann <kraxel@...hat.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Thomas Zimmermann <tzimmermann@...e.de>, Daniel Vetter <daniel@...ll.ch>
Subject: Re: [BUG][v6.9-rc6] Deadlock with: Revert "drm/qxl: simplify
 qxl_fence_wait"



On 2024-05-07 11:03, Steven Rostedt wrote:
> On Tue, 7 May 2024 15:54:21 +1000
> David Airlie <airlied@...hat.com> wrote:
> 
>> I expec this will reintroduce the other problems that caused this
>> change in the first place, but I think this should at least bring us
>> back to regression equilibrium. I can't recommend anyone use qxl hw
>> over virtio-gpu hw in their VMs, since virtio-gpu is actually hw
>> designed for virt.
> 
> I agree that it will likely cause the issues that this was addressing
> to come back, but you can't have a fix that introduces a deadlock.
> 
> Perhaps the deadlock didn't exist before, and the printk updates
> changed the way it works to introduce it now?
It deadlocks on 6.8.8 under qemu/kvm,  reverting the patch fixes the problem there as well (6.8.7 hangs as well, but I have not tested reverting on that version)

/Anders