linux-kernel - Re: [PATCH] cpufreq: Avoid cpufreq_suspend() deadlock on system shutdown

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Date:   Thu, 10 Oct 2019 12:23:02 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        Ville Syrjälä <ville.syrjala@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Stable <stable@...r.kernel.org>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] cpufreq: Avoid cpufreq_suspend() deadlock on system
 shutdown

On 09-10-19, 01:29, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> It is incorrect to set the cpufreq syscore shutdown callback pointer
> to cpufreq_suspend(), because that function cannot be run in the
> syscore stage of system shutdown for two reasons: (a) it may attempt
> to carry out actions depending on devices that have already been shut
> down at that point and (b) the RCU synchronization carried out by it
> may not be able to make progress then.
> 
> The latter issue has been present since commit 45975c7d21a1 ("rcu:
> Define RCU-sched API in terms of RCU for Tree RCU PREEMPT builds"),
> but the former one has always been there regardless.
> 
> Fix that by dropping cpufreq_syscore_ops altogether and making
> device_shutdown() call cpufreq_suspend() directly before shutting
> down devices, which is along the lines of what system-wide power
> management does.
> 
> Fixes: 45975c7d21a1 ("rcu: Define RCU-sched API in terms of RCU for Tree RCU PREEMPT builds")
> Reported-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
> Tested-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/base/core.c       |    3 +++
>  drivers/cpufreq/cpufreq.c |   10 ----------
>  2 files changed, 3 insertions(+), 10 deletions(-)

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh