Patch "drm/i915: Squelch any ktime/jiffie rounding errors for wait-ioctl" has been added to the 4.10-stable tree

This is a note to let you know that I've just added the patch titled

drm/i915: Squelch any ktime/jiffie rounding errors for wait-ioctl

to the 4.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-i915-squelch-any-ktime-jiffie-rounding-errors-for-wait-ioctl.patch
and it can be found in the queue-4.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Chris Wilson <[email protected]>
Date: Thu, 16 Feb 2017 12:54:41 +0000
Subject: drm/i915: Squelch any ktime/jiffie rounding errors for wait-ioctl

From: Chris Wilson <[email protected]>

commit 89cf83d4e065ff9fbd2ddc674489c8058eeca758 upstream.

We wait upon jiffies, but report the time elapsed using a high-resolution timer. This discrepancy can lead to us timing out the wait prior to us reporting the elapsed time as complete.

This restores the squelching lost in commit e95433c73a11 ("drm/i915:
Rearrange i915_wait_request() accounting with callers").

---
 drivers/gpu/drm/i915/i915_gem.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

@@ -3003,6 +3003,16 @@ i915_gem_wait_ioctl(struct drm_device *d
 		args->timeout_ns -= ktime_to_ns(ktime_sub(ktime_get(), start));
 		if (args->timeout_ns < 0)
 			args->timeout_ns = 0;
+
+		/*
+		 * Apparently ktime isn't accurate enough and occasionally has a
+		 * bit of mismatch in the jiffies<->nsecs<->ktime loop. So patch
+		 * things up to make the test happy. We allow up to 1 jiffy.
+		 *
+		 * This is a regression from the timespec->ktime conversion.
+		 */
+		if (ret == -ETIME && !nsecs_to_jiffies(args->timeout_ns))
+			args->timeout_ns = 0;
 	}
 
 	i915_gem_object_put(obj);

Patches currently in stable-queue which might be from [email protected] are

queue-4.10/drm-i915-squelch-any-ktime-jiffie-rounding-errors-for-wait-ioctl.patch queue-4.10/drm-i915-fbdev-stop-repeating-tile-configuration-on-stagnation.patch queue-4.10/drm-i915-store-a-permanent-error-in-obj-mm.pages.patch queue-4.10/drm-i915-gen9-increase-pcode-request-timeout-to-50ms.patch queue-4.10/drm-i915-avoid-tweaking-evaluation-thresholds-on-baytrail-v3.patch queue-4.10/drm-i915-fix-forcewake-active-domain-tracking.patch