cpufreq: Avoid cpufreq_suspend() deadlock on system shutdown
authorRafael J. Wysocki <rafael.j.wysocki@intel.com>
Tue, 8 Oct 2019 23:29:10 +0000 (01:29 +0200)
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>
Thu, 10 Oct 2019 09:11:17 +0000 (11:11 +0200)
commit65650b35133ff20f0c9ef0abd5c3c66dbce3ae57
tree9dccd5d41ec8481c183c6838676687bb194daf9c
parentda0c9ea146cbe92b832f1b0f694840ea8eb33cce
cpufreq: Avoid cpufreq_suspend() deadlock on system shutdown

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 been there since commit 90de2a4aa9f3 ("cpufreq:
suspend cpufreq governors on shutdown") 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")
Fixes: 90de2a4aa9f3 ("cpufreq: suspend cpufreq governors on shutdown")
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>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: 4.0+ <stable@vger.kernel.org> # 4.0+
drivers/base/core.c
drivers/cpufreq/cpufreq.c