Re: 5.3-rc3: Frozen graphics with kcompactd migrating i915 pages
From: Leho Kraav
Date: Tue Sep 10 2019 - 10:20:56 EST
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()")
Hi Chris. Is this exactly what I'm hitting at
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