[3.13.y.z extended stable] Patch "drm/i915: Reorder the semaphore deadlock check, again" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    drm/i915: Reorder the semaphore deadlock check, again

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.6.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 4a90a767bef36d599cc1245594b64abe12713954 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris at chris-wilson.co.uk>
Date: Sat, 19 Jul 2014 12:40:42 +0100
Subject: drm/i915: Reorder the semaphore deadlock check, again

commit a0d036b074b4a5a933e37fcb9bdd6b3cc80a0387 upstream.

commit 4be173813e57c7298103a83155c2391b5b167b4c
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Fri Jun 6 10:22:29 2014 +0100

    drm/i915: Reorder semaphore deadlock check

did the majority of the work, but it missed one crucial detail:

The check for the unkickable deadlock on this ring must come after the
check whether the ring that we are waiting on has already passed its
target seqno.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=80709
Tested-by: Stefan Huber <shuber at sthu.org>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at intel.com>
Cc: Jani Nikula <jani.nikula at intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/gpu/drm/i915/i915_irq.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 2093c72..3a10da2 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -2392,7 +2392,7 @@ static int semaphore_passed(struct intel_ring_buffer *ring)
 {
 	struct drm_i915_private *dev_priv = ring->dev->dev_private;
 	struct intel_ring_buffer *signaller;
-	u32 seqno, ctl;
+	u32 seqno;

 	ring->hangcheck.deadlock++;

@@ -2404,15 +2404,12 @@ static int semaphore_passed(struct intel_ring_buffer *ring)
 	if (signaller->hangcheck.deadlock >= I915_NUM_RINGS)
 		return -1;

-	/* cursory check for an unkickable deadlock */
-	ctl = I915_READ_CTL(signaller);
-	if (ctl & RING_WAIT_SEMAPHORE && semaphore_passed(signaller) < 0)
-		return -1;
-
 	if (i915_seqno_passed(signaller->get_seqno(signaller, false), seqno))
 		return 1;

-	if (signaller->hangcheck.deadlock)
+	/* cursory check for an unkickable deadlock */
+	if (I915_READ_CTL(signaller) & RING_WAIT_SEMAPHORE &&
+	    semaphore_passed(signaller) < 0)
 		return -1;

 	return 0;
--
1.9.1