Re: [2.6.33-rc5] Weird deadlock when shutting down

["Américo Wang" <xiyou.wangcong@gmail.com>]

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On Sat, Feb 20, 2010 at 9:57 PM, Johannes Berg
<johannes@sipsolutions.net> wrote:
> On Sat, 2010-02-20 at 21:44 +0800, Américo Wang wrote:
>
>> That message is displayed before shutting down the devices.
>>
>> To verify, you can add some printk() in the end of
>> __cpufreq_remove_dev(), or enable CONFIG_CPU_FREQ_DEBUG.
>
> That is already enabled.
>

Ok, I got it.

Could you test the patch below? Thanks!

----------------->

Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>

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diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 67bc2ec..e196084 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -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);