linux-kernel - Re: RFC on fixing mutex spinning on owner

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Message-ID: <alpine.DEB.2.11.1603171214530.3978@nanos>
Date:	Thu, 17 Mar 2016 12:16:11 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Nicholas Mc Guire <der.herr@...r.at>,
	Steven Rostedt <rostedt@...dmis.org>,
	Joel Fernandes <agnel.joel@...il.com>,
	Greg Kroah-Hartman <greg@...ah.com>,
	linux-rt-users@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	kernelnewbies <kernelnewbies@...linux.org>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: RFC on fixing mutex spinning on owner

On Thu, 17 Mar 2016, Peter Zijlstra wrote:
> Also, maybe the tracer should measure the time from need_resched()
> getting true until the next preemption point, instead of the entire time
> preemption was disabled. Which would avoid the entire issue altogether.

Well, that only gives you the information on a actual preemption, but not
information about long preempt disabled regions which can cause a problem
eventually.

Thanks,

	tglx