Date: Thu, 4 Mar 2010 03:23:46 -0500
From: Amerigo Wang <amwang@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: Dave Jones <davej@redhat.com>, cpufreq@vger.kernel.org,
Amerigo Wang <amwang@redhat.com>,
Johannes Berg <johannes@sipsolutions.net>, akpm@linux-foundation.org,
Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Subject: [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: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: WANG Cong <amwang@redhat.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Dave Jones <davej@redhat.com>
---
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);
--
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