Re: RFC on fixing mutex spinning on owner

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: RFC on fixing mutex spinning on owner
Date	2016-03-17 13:20 +0100
Message-ID	<rdF4e-7ki-7@gated-at.bofh.it> (permalink)
References	(4 earlier) <rdAHg-4j7-7@gated-at.bofh.it> <rdC6m-5mE-15@gated-at.bofh.it> <rdDc6-65q-11@gated-at.bofh.it> <rdE8a-6IF-21@gated-at.bofh.it> <rdEUy-7h0-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Mar 17, 2016 at 08:06:29AM -0400, Steven Rostedt wrote:
> On Thu, 17 Mar 2016 12:16:11 +0100 (CET)
> Thomas Gleixner <tglx@linutronix.de> wrote:
> 
> > 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.
> > 
> 
> Actually, I was thinking the reverse. If need_resched() is called and
> is false, then do a reset of the preemption time. But if need_resched()
> is true, then do nothing, as that would measure the total time preempt
> disable was set and a task could not schedule.
> 
> Question is, should this be a hook and each location audited, or add
> this to need_resched() itself?

Is anybody calling need_resched() and then not doing anything with the
value?

Thread

RFC on fixing mutex spinning on owner Joel Fernandes <agnel.joel@gmail.com> - 2016-03-17 00:30 +0100
  Re: RFC on fixing mutex spinning on owner Greg Kroah-Hartman <greg@kroah.com> - 2016-03-17 00:40 +0100
    Re: RFC on fixing mutex spinning on owner Joel Fernandes <agnel.joel@gmail.com> - 2016-03-17 00:40 +0100
      Re: RFC on fixing mutex spinning on owner Steven Rostedt <rostedt@goodmis.org> - 2016-03-17 03:20 +0100
        Re: RFC on fixing mutex spinning on owner Joel Fernandes <agnel.joel@gmail.com> - 2016-03-17 06:40 +0100
          Re: RFC on fixing mutex spinning on owner Steven Rostedt <rostedt@goodmis.org> - 2016-03-17 13:10 +0100
        Re: RFC on fixing mutex spinning on owner Peter Zijlstra <peterz@infradead.org> - 2016-03-17 08:40 +0100
          Re: RFC on fixing mutex spinning on owner Nicholas Mc Guire <der.herr@hofr.at> - 2016-03-17 10:10 +0100
            Re: RFC on fixing mutex spinning on owner Peter Zijlstra <peterz@infradead.org> - 2016-03-17 11:20 +0100
              Re: RFC on fixing mutex spinning on owner Thomas Gleixner <tglx@linutronix.de> - 2016-03-17 12:20 +0100
                Re: RFC on fixing mutex spinning on owner Steven Rostedt <rostedt@goodmis.org> - 2016-03-17 13:10 +0100
                Re: RFC on fixing mutex spinning on owner Peter Zijlstra <peterz@infradead.org> - 2016-03-17 13:20 +0100
                Re: RFC on fixing mutex spinning on owner Thomas Gleixner <tglx@linutronix.de> - 2016-03-17 14:40 +0100
                Re: RFC on fixing mutex spinning on owner Nicholas Mc Guire <der.herr@hofr.at> - 2016-03-17 17:50 +0100

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