<div class="gmail_quote">On Wed, Dec 14, 2011 at 10:57, Daniel Vetter <<a href="mailto:daniel.vetter@ffwll.ch">daniel.vetter@ffwll.ch</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> gpu reset is a very important piece of our infrastructure. Unfortunately we only really it test by actually hanging the gpu, which often has bad side-effects for the entire system. And the gpu hang handling code is one of the rather complicated pieces of code we have, consisting of - hang detection - error capture - actual gpu reset - reset of all the gem bookkeeping - reinitialition of the entire gpu This patch adds a debugfs to selectively stopping rings by ceasing to update the hw tail pointer, which will result in the gpu no longer updating it's head pointer and eventually to the hangcheck firing. This way we can exercise the gpu hang code under controlled conditions without a dying gpu taking down the entire systems. Patch motivated by me forgetting to properly reinitialize ppgtt after a gpu reset. Usage: echo $((1 << $ringnum)) > i915_ring_stop # stops one ring echo 0xffffffff > i915_ring_stop # stops all, future-proof version then run whatever testload is desired. i915_ring_stop automatically resets after a gpu hang is detected to avoid hanging the gpu to fast and declaring it wedged. v2: Incorporate feedback from Chris Wilson. v3: Add the missing cleanup. Signed-Off-by: Daniel Vetter <<a href="mailto:daniel.vetter@ffwll.ch">daniel.vetter@ffwll.ch</a>> Reviewed-by: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>> </blockquote><div> Reviewed-by: Eugeni Dodonov <<a href="mailto:eugeni.dodonov@intel.com">eugeni.dodonov@intel.com</a>> </div></div> -- Eugeni Dodonov<a href="http://eugeni.dodonov.net/" target="_blank"> </a>