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

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Message-ID: <20190912115851.GD6147@papaya>
Date:   Thu, 12 Sep 2019 14:58:51 +0300
From:   "leho@...av.com" <leho@...av.com>
To:     Martin Wilck <Martin.Wilck@...e.com>
Cc:     "chris@...is-wilson.co.uk" <chris@...is-wilson.co.uk>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        Michal Koutny <MKoutny@...e.com>,
        "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        "tiwai@...e.de" <tiwai@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: 5.3-rc3: Frozen graphics with kcompactd migrating i915 pages

On Thu, Sep 12, 2019 at 11:23:09AM +0000, Martin Wilck wrote:
> 
> There's a considerable risk that many users will start seeing this
> regression when 5.3 is released. I am not aware of a workaround.
> 
> Is there an alternative to reverting aa56a292ce62 ("drm/i915/userptr:
> Acquire the page lock around set_page_dirty()")? And if we do, what
> would be the consequences? Would other patches need to be reverted,
> too?

I've been running with revert patch for a couple of days and have not
encountered any kernel warnings thus far, nor any other ill effects that
could be attributed to this locking mechanism.

But I'm far from familiar with these subsystems.

Graphics does not hang anymore.

I've also received developer feedback in private that this really should
be fixed before 5.3 release.

-- 
Leho Kraav, senior technology & digital marketing architect