linux-kernel - Re: rcu self-detected stall messages on OMAP3, 4 boards

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Message-ID: <alpine.DEB.2.00.1209211803290.8839@utopia.booyaka.com>
Date:	Fri, 21 Sep 2012 18:08:59 +0000 (UTC)
From:	Paul Walmsley <paul@...an.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
cc:	"Bruce, Becky" <bbruce@...com>,
	"Paul E. McKenney" <paul.mckenney@...aro.org>,
	"<linux-kernel@...r.kernel.org>" <linux-kernel@...r.kernel.org>,
	"<linux-omap@...r.kernel.org>" <linux-omap@...r.kernel.org>,
	"<linux-arm-kernel@...ts.infradead.org>" 
	<linux-arm-kernel@...ts.infradead.org>,
	"Hilman, Kevin" <khilman@...com>,
	"Shilimkar, Santosh" <santosh.shilimkar@...com>,
	"Hunter, Jon" <jon-hunter@...com>,
	"<snijsure@...d-net.com>" <snijsure@...d-net.com>,
	fweisbec@...il.com
Subject: Re: rcu self-detected stall messages on OMAP3, 4 boards

cc Frederic Weisbecker - context is here: 

   http://marc.info/?l=linux-kernel&m=134749030206016&w=2

On Thu, 20 Sep 2012, Paul E. McKenney wrote:

> Fair point.  I am wondering whether there is some path into the idle
> loop that somehow avoids telling RCU that the CPU has in face entered
> idle.  There needs to be an rcu_idle_enter() call on the way to idle,
> otherwise RCU CPU stall warnings are expected behavior.

As far as I know, our only idle entry point is in 
arch/arm/common/process.c:cpu_idle().

Looking at the x86 idle entry, they call rcu_idle_{enter,exit}() inside 
{stop,start}_critical_timings().  Making that change here didn't help.

Also tried commenting out the code from the stop_critical_timings() call 
to the WARN_ON(irqs_disabled()), and adding a local_irq_enable().  That 
also didn't help, which suggests that the problem is not caused by the 
OMAP-specific PM idle code.


- Paul
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