From: Amerigo Wang <amwang@xxxxxxxxxx>
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
Signed-off-by: WANG Cong <amwang@xxxxxxxxxx>
Reported-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>
Cc: Dave Jones <davej@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/cpufreq/cpufreq.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)
diff -puN drivers/cpufreq/cpufreq.c~cpufreq-fix-a-lockdep-warning drivers/cpufreq/cpufreq.c
--- a/drivers/cpufreq/cpufreq.c~cpufreq-fix-a-lockdep-warning
+++ a/drivers/cpufreq/cpufreq.c
@@ -1109,6 +1109,8 @@ static int __cpufreq_remove_dev(struct s
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;
@@ -1137,10 +1139,11 @@ static int __cpufreq_remove_dev(struct s
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
@@ -1177,7 +1180,10 @@ static int __cpufreq_remove_dev(struct s
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);
}
}
@@ -1188,19 +1194,22 @@ static int __cpufreq_remove_dev(struct s
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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