[PATCH] s390: fix cmm kernel thread handling

Convert cmm's usage of kernel_thread to kthread_run. Also create the
cmmthread at module load time, so it is possible to check if creation of
the thread fails.

In addition the cmmthread now gets terminated when the module gets unloaded
instead of leaving a stale kernel thread. Also check the return values of
other registration functions at module load and handle their return values
appropriately.

Cc: Martin Schwidefsky <[e-mail]>
Signed-off-by: Heiko Carstens <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/s390/mm/cmm.c

···
 #include <linux/sysctl.h>
 #include <linux/ctype.h>
 #include <linux/swap.h>
+#include <linux/kthread.h>
 
 #include <asm/pgalloc.h>
 #include <asm/uaccess.h>
···
 static struct cmm_page_array *cmm_timed_page_list;
 static DEFINE_SPINLOCK(cmm_lock);
 
-static unsigned long cmm_thread_active;
-static struct work_struct cmm_thread_starter;
+static struct task_struct *cmm_thread_ptr;
 static wait_queue_head_t cmm_thread_wait;
 static struct timer_list cmm_timer;
 
···
 {
 	int rc;
 
-	daemonize("cmmthread");
 	while (1) {
 		rc = wait_event_interruptible(cmm_thread_wait,
 			(cmm_pages != cmm_pages_target ||
-			 cmm_timed_pages != cmm_timed_pages_target));
-		if (rc == -ERESTARTSYS) {
-			/* Got kill signal. End thread. */
-			clear_bit(0, &cmm_thread_active);
+			 cmm_timed_pages != cmm_timed_pages_target ||
+			 kthread_should_stop()));
+		if (kthread_should_stop() || rc == -ERESTARTSYS) {
 			cmm_pages_target = cmm_pages;
 			cmm_timed_pages_target = cmm_timed_pages;
 			break;
···
 }
 
 static void
-cmm_start_thread(void)
-{
-	kernel_thread(cmm_thread, NULL, 0);
-}
-
-static void
 cmm_kick_thread(void)
 {
-	if (!test_and_set_bit(0, &cmm_thread_active))
-		schedule_work(&cmm_thread_starter);
 	wake_up(&cmm_thread_wait);
 }
 
···
 static int
 cmm_init (void)
 {
+	int rc = -ENOMEM;
+
 #ifdef CONFIG_CMM_PROC
 	cmm_sysctl_header = register_sysctl_table(cmm_dir_table, 1);
+	if (!cmm_sysctl_header)
+		goto out;
 #endif
 #ifdef CONFIG_CMM_IUCV
-	smsg_register_callback(SMSG_PREFIX, cmm_smsg_target);
+	rc = smsg_register_callback(SMSG_PREFIX, cmm_smsg_target);
+	if (rc < 0)
+		goto out_smsg;
 #endif
-	register_oom_notifier(&cmm_oom_nb);
-	INIT_WORK(&cmm_thread_starter, (void *) cmm_start_thread, NULL);
+	rc = register_oom_notifier(&cmm_oom_nb);
+	if (rc < 0)
+		goto out_oom_notify;
 	init_waitqueue_head(&cmm_thread_wait);
 	init_timer(&cmm_timer);
-	return 0;
+	cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread");
+	rc = IS_ERR(cmm_thread_ptr) ? PTR_ERR(cmm_thread_ptr) : 0;
+	if (!rc)
+		goto out;
+	/*
+	 * kthread_create failed. undo all the stuff from above again.
+	 */
+	unregister_oom_notifier(&cmm_oom_nb);
+
+out_oom_notify:
+#ifdef CONFIG_CMM_IUCV
+	smsg_unregister_callback(SMSG_PREFIX, cmm_smsg_target);
+out_smsg:
+#endif
+#ifdef CONFIG_CMM_PROC
+	unregister_sysctl_table(cmm_sysctl_header);
+#endif
+out:
+	return rc;
 }
 
 static void
 cmm_exit(void)
 {
+	kthread_stop(cmm_thread_ptr);
 	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);