From: Peter Zijlstra <peterz@infradead.org>
To: Chen Yu <yu.c.chen@intel.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Ingo Molnar <mingo@kernel.org>, Len Brown <len.brown@intel.com>,
linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH][RFC] PM / s2idle: Clear _TIF_POLLING_NRFLAG before suspend to idle
Date: Mon, 15 Jun 2020 21:31:54 +0200 [thread overview]
Message-ID: <20200615193154.GJ2554@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200615184041.GG2531@hirez.programming.kicks-ass.net>
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().
Something like so then. Your version is racy, if someone already set
TIF_NEED_RESCHED you just clear POLLING and go to sleep.
---
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;
}
next prev parent reply other threads:[~2020-06-15 19:32 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-15 17:36 [PATCH][RFC] PM / s2idle: Clear _TIF_POLLING_NRFLAG before suspend to idle Chen Yu
2020-06-15 18:40 ` Peter Zijlstra
2020-06-15 19:31 ` Peter Zijlstra [this message]
2020-06-16 3:36 ` Chen Yu
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