[S390] cmm: fix crash on module unload

There might be a scheduled cmm_timer if the cmm module gets unloaded.
That timer was not deleted during module unload and thus could lead
to system crash later on.
Besides that reorder function calls in module init and exit code to
avoid a couple of other races which could lead to accesses to
uninitialized data.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/mm/cmm.c

@@ -53,8 +53,8 @@ static struct cmm_page_array *cmm_timed_page_list;
 static DEFINE_SPINLOCK(cmm_lock);
 
 static struct task_struct *cmm_thread_ptr;
-static wait_queue_head_t cmm_thread_wait;
-static struct timer_list cmm_timer;
+static DECLARE_WAIT_QUEUE_HEAD(cmm_thread_wait);
+static DEFINE_TIMER(cmm_timer, NULL, 0, 0);
 
 static void cmm_timer_fn(unsigned long);
 static void cmm_set_timer(void);
@@ -466,8 +466,6 @@ cmm_init (void)
 	rc = register_pm_notifier(&cmm_power_notifier);
 	if (rc)
 		goto out_pm;
-	init_waitqueue_head(&cmm_thread_wait);
-	init_timer(&cmm_timer);
 	cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread");
 	rc = IS_ERR(cmm_thread_ptr) ? PTR_ERR(cmm_thread_ptr) : 0;
 	if (rc)
@@ -487,23 +485,25 @@ cmm_init (void)
 	unregister_sysctl_table(cmm_sysctl_header);
 out_sysctl:
 #endif
+	del_timer_sync(&cmm_timer);
 	return rc;
 }
 
 static void
 cmm_exit(void)
 {
-	kthread_stop(cmm_thread_ptr);
-	unregister_pm_notifier(&cmm_power_notifier);
-	unregister_oom_notifier(&cmm_oom_nb);
-	cmm_free_pages(cmm_pages, &cmm_pages, &cmm_page_list);
-	cmm_free_pages(cmm_timed_pages, &cmm_timed_pages, &cmm_timed_page_list);
 #ifdef CONFIG_CMM_PROC
 	unregister_sysctl_table(cmm_sysctl_header);
 #endif
 #ifdef CONFIG_CMM_IUCV
 	smsg_unregister_callback(SMSG_PREFIX, cmm_smsg_target);
 #endif
+	unregister_pm_notifier(&cmm_power_notifier);
+	unregister_oom_notifier(&cmm_oom_nb);
+	kthread_stop(cmm_thread_ptr);
+	del_timer_sync(&cmm_timer);
+	cmm_free_pages(cmm_pages, &cmm_pages, &cmm_page_list);
+	cmm_free_pages(cmm_timed_pages, &cmm_timed_pages, &cmm_timed_page_list);
 }
 
 module_init(cmm_init);