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Date: Wed, 16 Mar 2016 16:38:56 -0700 From: Joel Fernandes <agnel.joel@...il.com> To: Greg Kroah-Hartman <greg@...ah.com> Cc: linux-rt-users@...r.kernel.org, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, kernelnewbies <kernelnewbies@...linux.org>, Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de> Subject: Re: RFC on fixing mutex spinning on owner Hi Greg, On Wed, Mar 16, 2016 at 4:35 PM, Greg Kroah-Hartman <greg@...ah.com> 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
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