Commit c1d2061b authored Feb 16, 2017 by Chris Wilson

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



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 e95433c7 ("drm/i915:
Rearrange i915_wait_request() accounting with callers").

Fixes: e95433c7 ("drm/i915: Rearrange i915_wait_request() accounting with callers")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: <drm-intel-fixes@lists.freedesktop.org> # v4.10-rc1+
Cc: stable@vger.kernel.org
Link: http://patchwork.freedesktop.org/patch/msgid/20170216125441.30923-1-chris@chris-wilson.co.uk


Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

parent bbdf0b2f

drivers/gpu/drm/i915/i915_gem.c

+10 −0

Original line number	Original line	Diff line number	Diff line
	@@ -3072,6 +3072,16 @@ i915_gem_wait_ioctl(struct drm_device dev, void data, struct drm_file *file)
	args->timeout_ns -= ktime_to_ns(ktime_sub(ktime_get(), start));		args->timeout_ns -= ktime_to_ns(ktime_sub(ktime_get(), start));
	if (args->timeout_ns < 0)		if (args->timeout_ns < 0)
	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);		i915_gem_object_put(obj);