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Date: Tue, 16 Jun 2020 11:36:18 +0800 From: Chen Yu <yu.c.chen@...el.com> To: Peter Zijlstra <peterz@...radead.org> Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Daniel Lezcano <daniel.lezcano@...aro.org>, Ingo Molnar <mingo@...nel.org>, Len Brown <len.brown@...el.com>, linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH][RFC] PM / s2idle: Clear _TIF_POLLING_NRFLAG before suspend to idle On Mon, Jun 15, 2020 at 09:31:54PM +0200, Peter Zijlstra wrote: > On Mon, Jun 15, 2020 at 08:40:41PM +0200, Peter Zijlstra wrote: > > > > @@ -186,8 +187,10 @@ int cpuidle_enter_s2idle(struct cpuidle_driver *drv, struct cpuidle_device *dev) > > > * be frozen safely. > > > */ > > > index = find_deepest_state(drv, dev, U64_MAX, 0, true); > > > - if (index > 0) > > > + if (index > 0) { > > > + __current_clr_polling(); > > > enter_s2idle_proper(drv, dev, index); > > > + } > > > > > > return index; > > > } > > > > So how is that commit 08e237fa56a1 not suffient? That makes > > mwait_idle_with_hints() DTRT for this 'functionally challenged' piece of > > hardware. > > > > AFAICT intel_enter_s2idle() uses mwait_idle_with_hints(). > > > > What am I missing? > > What's missing is that cpuidle_enter_s2idle() doesn't properly match > call_cpuidle(). > Right. > Something like so then. Your version is racy, if someone already set > TIF_NEED_RESCHED you just clear POLLING and go to sleep. > Got it, I'll test the patch below. Thanks, Chenyu > --- > > diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c > index c149d9e20dfd..81bee8d03c6d 100644 > --- a/drivers/cpuidle/cpuidle.c > +++ b/drivers/cpuidle/cpuidle.c > @@ -133,8 +133,8 @@ int cpuidle_find_deepest_state(struct cpuidle_driver *drv, > } > > #ifdef CONFIG_SUSPEND > -static void enter_s2idle_proper(struct cpuidle_driver *drv, > - struct cpuidle_device *dev, int index) > +static void s2idle_enter(struct cpuidle_driver *drv, > + struct cpuidle_device *dev, int index) > { > ktime_t time_start, time_end; > > @@ -168,6 +168,15 @@ static void enter_s2idle_proper(struct cpuidle_driver *drv, > dev->states_usage[index].s2idle_usage++; > } > > +static int call_s2idle(struct cpuidle_driver *drv, struct cpuidle_device *dev, > + int index) > +{ > + if (!current_clr_polling_and_test()) > + s2idle_enter(drv, dev, index); > + > + return index; > +} > + > /** > * cpuidle_enter_s2idle - Enter an idle state suitable for suspend-to-idle. > * @drv: cpuidle driver for the given CPU. > @@ -187,7 +196,7 @@ int cpuidle_enter_s2idle(struct cpuidle_driver *drv, struct cpuidle_device *dev) > */ > index = find_deepest_state(drv, dev, U64_MAX, 0, true); > if (index > 0) > - enter_s2idle_proper(drv, dev, index); > + call_s2idle(drv, dev, index); > > return index; > }
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