Commit 499bca9b authored by Amerigo Wang's avatar Amerigo Wang Committed by Dave Jones
Browse files

[CPUFREQ] fix a lockdep warning 



There is no need to do sysfs_remove_link() or kobject_put() etc.
when policy_rwsem_write is held, move them after releasing the lock.

This fixes the lockdep warning:

halt/4071 is trying to acquire lock:
 (s_active){++++.+}, at: [<c0000000001ef868>] .sysfs_addrm_finish+0x58/0xc0

but task is already holding lock:
 (&per_cpu(cpu_policy_rwsem, cpu)){+.+.+.}, at: [<c0000000004cd6ac>] .lock_policy_rwsem_write+0x84/0xf4

Reported-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: default avatarWANG Cong <amwang@redhat.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: default avatarDave Jones <davej@redhat.com>
parent 2eaa9cfd

drivers/cpufreq/cpufreq.c

+14 −5
Original line number Diff line number Diff line
@@ -1113,6 +1113,8 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev) 
	unsigned int cpu = sys_dev->id;

	unsigned long flags;

	struct cpufreq_policy *data;

	struct kobject *kobj;

	struct completion *cmp;

#ifdef CONFIG_SMP

	struct sys_device *cpu_sys_dev;

	unsigned int j;
@@ -1141,10 +1143,11 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev) 
		dprintk("removing link\n");

		cpumask_clear_cpu(cpu, data->cpus);

		spin_unlock_irqrestore(&cpufreq_driver_lock, flags);

		sysfs_remove_link(&sys_dev->kobj, "cpufreq");

		kobj = &sys_dev->kobj;

		cpufreq_cpu_put(data);

		cpufreq_debug_enable_ratelimit();

		unlock_policy_rwsem_write(cpu);

		sysfs_remove_link(kobj, "cpufreq");

		return 0;

	}

#endif
@@ -1181,7 +1184,10 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev) 
				data->governor->name, CPUFREQ_NAME_LEN);

#endif

			cpu_sys_dev = get_cpu_sysdev(j);

			sysfs_remove_link(&cpu_sys_dev->kobj, "cpufreq");

			kobj = &cpu_sys_dev->kobj;

			unlock_policy_rwsem_write(cpu);

			sysfs_remove_link(kobj, "cpufreq");

			lock_policy_rwsem_write(cpu);

			cpufreq_cpu_put(data);

		}

	}
@@ -1192,19 +1198,22 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev) 
	if (cpufreq_driver->target)

		__cpufreq_governor(data, CPUFREQ_GOV_STOP);



	kobject_put(&data->kobj);

	kobj = &data->kobj;

	cmp = &data->kobj_unregister;

	unlock_policy_rwsem_write(cpu);

	kobject_put(kobj);



	/* we need to make sure that the underlying kobj is actually

	 * not referenced anymore by anybody before we proceed with

	 * unloading.

	 */

	dprintk("waiting for dropping of refcount\n");

	wait_for_completion(&data->kobj_unregister);

	wait_for_completion(cmp);

	dprintk("wait complete\n");



	lock_policy_rwsem_write(cpu);

	if (cpufreq_driver->exit)

		cpufreq_driver->exit(data);



	unlock_policy_rwsem_write(cpu);



	free_cpumask_var(data->related_cpus);

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