linux-kernel - Re: [PATCH][Fix] cpuidle: Run tick_broadcast

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Message-ID: <1934706.ixTLMcGVHV@vostro.rjw.lan>
Date:	Fri, 01 May 2015 00:10:35 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:	Sudeep Holla <sudeep.holla@....com>,
	Peter Zijlstra <peterz@...radead.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH][Fix] cpuidle: Run tick_broadcast_exit() with disabled interrupts

On Thursday, April 30, 2015 04:12:46 PM Nicolas Pitre wrote:
> On Wed, 29 Apr 2015, Rafael J. Wysocki wrote:
> 
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > 
> > Commit 335f49196fd6 (sched/idle: Use explicit broadcast oneshot
> > control function) replaced clockevents_notify() invocations in
> > cpuidle_idle_call() with direct calls to tick_broadcast_enter()
> > and tick_broadcast_exit(), but it overlooked the fact that
> > interrupts were already enabled before calling the latter which
> > led to functional breakage on systems using idle states with the
> > CPUIDLE_FLAG_TIMER_STOP flag set.
> > 
> > Fix that by moving the invocations of tick_broadcast_enter()
> > and tick_broadcast_exit() down into cpuidle_enter_state() where
> > interrupts are still disabled when tick_broadcast_exit() is
> > called.  Also ensure that interrupts will be disabled before
> > running tick_broadcast_exit() even if they have been enabled by
> > the idle state's ->enter callback.  Trigger a WARN_ON_ONCE() in
> > that case, as we generally don't want that to happen for states
> > with CPUIDLE_FLAG_TIMER_STOP set.
> 
> Incidentally I was debugging this issue as well when I saw this thread.
> 
> And it turns out that I did report this issue 2 months ago:
> http://article.gmane.org/gmane.linux.kernel/1892049
> What happened?

The patch series had been picked up by someone else (me), reordered and rebased
in the meantime and your report was missed.  Sorry about that.

> > Fixes: 335f49196fd6 (sched/idle: Use explicit broadcast oneshot control function)
> > Reported-and-tested-by: Linus Walleij <linus.walleij@...aro.org>
> > Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> > Reported-and-tested-by: Sudeep Holla <sudeep.holla@....com>
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Tested-by: Nicolas Pitre <nico@...aro.org>

Thanks!


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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