From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Mon, 10 Jun 2013 10:20:21 +0000 (+0100)
Subject: drm/i915: Don't count semaphore waits towards a stuck ring
X-Git-Tag: v3.11-rc1~65^2~61^2~25
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6274f2126a0454d3c3df1bc9cc6f5e18302696f7;p=pandora-kernel.git

drm/i915: Don't count semaphore waits towards a stuck ring

If we detect a ring is in a valid wait for another, just let it be.
Eventually it will either begin to progress again, or the entire system
will come grinding to a halt and then hangcheck will fire as soon as the
deadlock is detected.

This error was foretold by Ben in
commit 05407ff889ceebe383aa5907219f86582ef96b72
Author: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Date:   Thu May 30 09:04:29 2013 +0300

    drm/i915: detect hang using per ring hangcheck_score

"If ring B is waiting on ring A via semaphore, and ring A is making
progress, albeit slowly - the hangcheck will fire. The check will
determine that A is moving, however ring B will appear hung because
the ACTHD doesn't move. I honestly can't say if that's actually a
realistic problem to hit it probably implies the timeout value is too
low."

v2: Make sure we don't even incur the KICK cost whilst waiting.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=65394
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---

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