[PATCH] Fix SAK_work workqueue initialization.

Somewhere in the rewrite of the work queues my cleanup of SAK handling
got broken.  Maybe I didn't retest it properly or possibly the API
was changing so fast I missed something.  Regardless currently
triggering a SAK now generates an ugly BUG_ON and kills the kernel.

Thanks to Alexey Dobriyan <adobriyan@openvz.org> for spotting this.

This modifies the use of SAK_work to initialize it when the data
structure it resides in is initialized, and to simply call
schedule_work when we need to generate a SAK.  I update both
data structures that have a SAK_work member for consistency.

All of the old PREPARE_WORK calls that are now gone.

If we call schedule_work again before it has processed it
has generated the first SAK it will simply ignore the duplicate
schedule_work request.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/keyboard.c

@@ -596,7 +596,6 @@ static void fn_spawn_con(struct vc_data *vc)
 static void fn_SAK(struct vc_data *vc)
 {
 	struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
-	PREPARE_WORK(SAK_work, vc_SAK);
 	schedule_work(SAK_work);
 }
 

drivers/char/sysrq.c

@@ -89,7 +89,6 @@ static struct sysrq_key_op sysrq_loglevel_op = {
 static void sysrq_handle_SAK(int key, struct tty_struct *tty)
 {
 	struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
-	PREPARE_WORK(SAK_work, vc_SAK);
 	schedule_work(SAK_work);
 }
 static struct sysrq_key_op sysrq_SAK_op = {

drivers/char/tty_io.c

@@ -3442,7 +3442,6 @@ void do_SAK(struct tty_struct *tty)
 {
 	if (!tty)
 		return;
-	PREPARE_WORK(&tty->SAK_work, do_SAK_work);
 	schedule_work(&tty->SAK_work);
 }
 
@@ -3568,7 +3567,7 @@ static void initialize_tty_struct(struct tty_struct *tty)
 	mutex_init(&tty->atomic_write_lock);
 	spin_lock_init(&tty->read_lock);
 	INIT_LIST_HEAD(&tty->tty_files);
-	INIT_WORK(&tty->SAK_work, NULL);
+	INIT_WORK(&tty->SAK_work, do_SAK_work);
 }
 
 /*

drivers/char/vt.c

@@ -2635,6 +2635,7 @@ static int __init con_init(void)
 	 */
 	for (currcons = 0; currcons < MIN_NR_CONSOLES; currcons++) {
 		vc_cons[currcons].d = vc = alloc_bootmem(sizeof(struct vc_data));
+		INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK);
 		visual_init(vc, currcons, 1);
 		vc->vc_screenbuf = (unsigned short *)alloc_bootmem(vc->vc_screenbuf_size);
 		vc->vc_kmalloced = 0;