diff mbox series

[v1,3/3] cpufreq: Rearrange locking in cpufreq_remove_dev()

Message ID 1836239.tdWV9SEqCh@kreacher
State New
Headers show
Series cpufreq: Locking-related changes in cpufreq_offline() and cpufreq_remove_dev() | expand

Commit Message

Rafael J. Wysocki May 11, 2022, 3:51 p.m. UTC 
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Currently, cpufreq_remove_dev() invokes the ->exit() driver callback
without holding the policy rwsem which is inconsistent with what
happens if ->exit() is invoked directly from cpufreq_offline().

It also manipulates the real_cpus mask and removes the CPU device
symlink without holding the policy rwsem, but cpufreq_offline() holds
the rwsem around the modifications thereof.

For consistency, modify cpufreq_remove_dev() to hold the policy rwsem
until the ->exit() callback has been called (or it has been determined
that it is not necessary to call it).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/cpufreq/cpufreq.c |   21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

Comments

Viresh Kumar May 12, 2022, 7:42 a.m. UTC | #1 
On 11-05-22, 17:51, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> Currently, cpufreq_remove_dev() invokes the ->exit() driver callback
> without holding the policy rwsem which is inconsistent with what
> happens if ->exit() is invoked directly from cpufreq_offline().
> 
> It also manipulates the real_cpus mask and removes the CPU device
> symlink without holding the policy rwsem, but cpufreq_offline() holds
> the rwsem around the modifications thereof.
> 
> For consistency, modify cpufreq_remove_dev() to hold the policy rwsem
> until the ->exit() callback has been called (or it has been determined
> that it is not necessary to call it).
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
>  drivers/cpufreq/cpufreq.c |   21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)

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

Patch

Index: linux-pm/drivers/cpufreq/cpufreq.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq.c
+++ linux-pm/drivers/cpufreq/cpufreq.c
@@ -1659,19 +1659,26 @@  static void cpufreq_remove_dev(struct de
 	if (!policy)
 		return;
 
+	down_write(&policy->rwsem);
+
 	if (cpu_online(cpu))
-		cpufreq_offline(cpu);
+		__cpufreq_offline(cpu, policy);
 
 	cpumask_clear_cpu(cpu, policy->real_cpus);
 	remove_cpu_dev_symlink(policy, dev);
 
-	if (cpumask_empty(policy->real_cpus)) {
-		/* We did light-weight exit earlier, do full tear down now */
-		if (cpufreq_driver->offline)
-			cpufreq_driver->exit(policy);
-
-		cpufreq_policy_free(policy);
+	if (!cpumask_empty(policy->real_cpus)) {
+		up_write(&policy->rwsem);
+		return;
 	}
+
+	/* We did light-weight exit earlier, do full tear down now */
+	if (cpufreq_driver->offline)
+		cpufreq_driver->exit(policy);
+
+	up_write(&policy->rwsem);
+
+	cpufreq_policy_free(policy);
 }
 
 /**