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Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods
Date 2017-07-20 16:30 +0200
Message-ID <u5kCJ-ew-9@gated-at.bofh.it> (permalink)
References (5 earlier) <u4CBH-45e-9@gated-at.bofh.it> <u4Q1X-49w-3@gated-at.bofh.it> <u4Ysy-1t8-9@gated-at.bofh.it> <u58Lg-cj-3@gated-at.bofh.it> <u5jdE-7zI-15@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Thu, Jul 20, 2017 at 05:50:54AM -0700, Paul E. McKenney wrote:
> > 
> > static void cpuidle_idle_call()
> > {
> > 	rcu_idle_enter()
> > 	......
> > 	rcu_idle_exit()
> > }
> > 
> > I want
> > 
> > static void cpuidle_idle_call()
> > {
> > 	if (tick stopped)
> > 		rcu_idle_enter()
> > 	......
> > 	if (tick stopped)
> > 		rcu_idle_exit()
> > }
> >
> > Or checking tick stop can be put into rcu_idle_enter/exit
> 
> The answer is the traditional "it depends".
> 
> If the above change was all that you did, that would be a bug in the
> case where the predicted short idle time turned out to in reality be an
> indefinite idle time. 

Can't be, you didn't disable the tick after all, so you're guaranteed to
get interrupted by the tick and try again.

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Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-18 17:30 +0200
  Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Arjan van de Ven <arjan@linux.intel.com> - 2017-07-18 17:30 +0200
    Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Arjan van de Ven <arjan@linux.intel.com> - 2017-07-18 18:40 +0200
      Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-18 19:10 +0200
    Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-18 18:40 +0200
  Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-19 07:50 +0200
    Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-19 16:50 +0200
      Re: [RFC PATCH v1 00/11] Create fast idle path for short idle  periods Christopher Lameter <cl@linux.com> - 2017-07-19 17:10 +0200
        Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-19 19:00 +0200
      Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-20 03:50 +0200
        Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-20 15:00 +0200
          Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Arjan van de Ven <arjan@linux.intel.com> - 2017-07-20 15:50 +0200
          Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-20 16:30 +0200
            Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-20 18:10 +0200

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