Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966981AbcCPXjA (ORCPT ); Wed, 16 Mar 2016 19:39:00 -0400 Received: from mail-lf0-f54.google.com ([209.85.215.54]:36382 "EHLO mail-lf0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752107AbcCPXi6 (ORCPT ); Wed, 16 Mar 2016 19:38:58 -0400 MIME-Version: 1.0 In-Reply-To: <20160316233530.GA8731@kroah.com> References: <20160316233530.GA8731@kroah.com> Date: Wed, 16 Mar 2016 16:38:56 -0700 Message-ID: Subject: Re: RFC on fixing mutex spinning on owner From: Joel Fernandes To: Greg Kroah-Hartman Cc: linux-rt-users@vger.kernel.org, Linux Kernel Mailing List , kernelnewbies , Steven Rostedt , Ingo Molnar , Peter Zijlstra , Thomas Gleixner Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 999 Lines: 26 Hi Greg, On Wed, Mar 16, 2016 at 4:35 PM, Greg Kroah-Hartman wrote: > On Wed, Mar 16, 2016 at 04:22:17PM -0700, Joel Fernandes wrote: >> Hi, >> >> On a fairly recent kernel and android userspace, I am seeing that with >> i915 driver is in a spin loop waiting for mutex owner to release it >> (mutex_spin_on_owner). > > Why not provide a backtrace to the drm and i915 developers so that they > can work on this? The mailing lists you sent this to can't do much > about this, sorry... I am not sure if the problem is with the i915 driver, because the mutex spin on owner stuff is mutex related so the mutex design may potentially need a tweak (I mentioned a proposal of adding mutex spinning time outs). Also since this is latency issue related (I mentioned preemptoff tracer and preempt disabled), I sent it to linux-rt-users. Thanks for the tip about sending it to i915 developers, incase no one here has a say in the matter, I can drop them a note later as well. Thanks, Joel