linux-kernel - Re: Regression with suspicious RCU usage splats with cpu

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Message-Id: <20170713124318.GK2393@linux.vnet.ibm.com>
Date:   Thu, 13 Jul 2017 05:43:18 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Alex Shi <alex.shi@...aro.org>, Tony Lindgren <tony@...mide.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <Will.Deacon@....com>
Subject: Re: Regression with suspicious RCU usage splats with cpu_pm change

On Thu, Jul 13, 2017 at 01:50:26PM +0200, Rafael J. Wysocki wrote:
> On Thu, Jul 13, 2017 at 11:43 AM, Alex Shi <alex.shi@...aro.org> wrote:
> >
> > On 07/13/2017 03:07 PM, Tony Lindgren wrote:
> >> Hi,
> >>
> >> Looks like next-20170713 gives me a bunch of "suspicious RCU usage"
> >> splats with cpuidle_coupled on duovero, see below. I bisected it down
> >> to commit 2f027e003d05 ("cpu_pm: replace raw_notifier with
> >> atomic_notifier").
> 
> OK, so I'm dropping this commit.

You can surround idle-loop RCU-reading code with RCU_NONIDLE().
This will tell RCU to pay attention even though the CPU is otherwise
idle.

							Thanx, Paul