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

[Viresh Kumar <viresh.kumar@linaro.org>]

On 09-10-19, 01:29, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.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@linux.intel.com>
> Tested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
>  drivers/base/core.c       |    3 +++
>  drivers/cpufreq/cpufreq.c |   10 ----------
>  2 files changed, 3 insertions(+), 10 deletions(-)

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

-- 
viresh