cpufreq: Avoid cpufreq_suspend() deadlock on system shutdown
diff mbox series

Message ID 10202295.pfq90QWH5T@kreacher
State Awaiting Upstream
Delegated to: Rafael Wysocki
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Series
  • cpufreq: Avoid cpufreq_suspend() deadlock on system shutdown
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Commit Message

Rafael J. Wysocki Oct. 8, 2019, 11:29 p.m. UTC
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(-)

Comments

Viresh Kumar Oct. 10, 2019, 6:53 a.m. UTC | #1
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>

Patch
diff mbox series

Index: linux-pm/drivers/cpufreq/cpufreq.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq.c
+++ linux-pm/drivers/cpufreq/cpufreq.c
@@ -2737,14 +2737,6 @@  int cpufreq_unregister_driver(struct cpu
 }
 EXPORT_SYMBOL_GPL(cpufreq_unregister_driver);
 
-/*
- * Stop cpufreq at shutdown to make sure it isn't holding any locks
- * or mutexes when secondary CPUs are halted.
- */
-static struct syscore_ops cpufreq_syscore_ops = {
-	.shutdown = cpufreq_suspend,
-};
-
 struct kobject *cpufreq_global_kobject;
 EXPORT_SYMBOL(cpufreq_global_kobject);
 
@@ -2756,8 +2748,6 @@  static int __init cpufreq_core_init(void
 	cpufreq_global_kobject = kobject_create_and_add("cpufreq", &cpu_subsys.dev_root->kobj);
 	BUG_ON(!cpufreq_global_kobject);
 
-	register_syscore_ops(&cpufreq_syscore_ops);
-
 	return 0;
 }
 module_param(off, int, 0444);
Index: linux-pm/drivers/base/core.c
===================================================================
--- linux-pm.orig/drivers/base/core.c
+++ linux-pm/drivers/base/core.c
@@ -9,6 +9,7 @@ 
  */
 
 #include <linux/acpi.h>
+#include <linux/cpufreq.h>
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/fwnode.h>
@@ -3179,6 +3180,8 @@  void device_shutdown(void)
 	wait_for_device_probe();
 	device_block_probing();
 
+	cpufreq_suspend();
+
 	spin_lock(&devices_kset->list_lock);
 	/*
 	 * Walk the devices list backward, shutting down each in turn.