linux-kernel - Re: 5.3-rc3: Frozen graphics with kcompactd migrating i915 pages

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Message-ID: <20190910142047.GB3029@papaya>
Date:   Tue, 10 Sep 2019 17:20:47 +0300
From:   Leho Kraav <leho@...av.com>
To:     Chris Wilson <chris@...is-wilson.co.uk>
Cc:     "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        Martin Wilck <Martin.Wilck@...e.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: 5.3-rc3: Frozen graphics with kcompactd migrating i915 pages

On Fri, Aug 09, 2019 at 01:53:43PM +0100, Chris Wilson wrote:
> Quoting Martin Wilck (2019-08-09 13:41:42)
> > This happened to me today, running kernel 5.3.0-rc3-1.g571863b-default
> > (5.3-rc3 with just a few patches on top), after starting a KVM virtual
> > machine. The X screen was frozen. Remote login via ssh was still
> > possible, thus I was able to retrieve basic logs.
> > 
> > sysrq-w showed two blocked processes (kcompactd0 and KVM). After a
> > minute, the same two processes were still blocked. KVM seems to try to
> > acquire a lock that kcompactd is holding. kcompactd is waiting for IO
> > to complete on pages owned by the i915 driver.
> 
> My bad, it's known. We haven't decided on whether to revert the
> unfortunate recursive locking (and so hit another warn elsewhere) or to
> ignore the dirty pages (and so risk losing data across swap).
> 
> cb6d7c7dc7ff ("drm/i915/userptr: Acquire the page lock around set_page_dirty()")
> -Chris

Hi Chris. Is this exactly what I'm hitting at
https://bugs.freedesktop.org/show_bug.cgi?id=111500 perhaps?

It reliably breaks the graphics userland, as the machine consistently
freezes at any random moment.

Any workaround options, even if with a performance penalty? Revert
cb6d7c7dc7ff but side effects?

5.3 has useful NVMe power mgmt updates for laptops, I'd like to stick
with the newest if possible.

-- 
Leho Kraav, senior technology & digital marketing architect