[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>

1 files changed, 14 insertions, 5 deletions

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 2d5d575e889d..75d293eeb3ee 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);