vt: bitlock fix

PATCH New Nick Piggin 1 participant 1 message Nov 20, 2007 Char and misc drivers

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Nick Piggin

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2007-11-20 05:14 UTC #0 lore raw

PATCH 1/1 vt: bitlock fix

Don't know who maintains vt.c, but Antonino's name comes up regularly ;)

--
vt is missing a memory barrier to close the critical section. Use a real spinlock for this.

Signed-off-by Nick Piggin <[email protected]>

---

drivers/char/vt.c +5 -3

Index: linux-2.6/drivers/char/vt.c
===================================================================
@@ -2400,13 +2400,15 @@ static void vt_console_print(struct cons
 {
 	struct vc_data *vc = vc_cons[fg_console].d;
 	unsigned char c;
-	static unsigned long printing;
+	static DEFINE_SPINLOCK(printing_lock);
 	const ushort *start;
 	ushort cnt = 0;
 	ushort myx;
 
 	/* console busy or not yet initialized */
-	if (!printable || test_and_set_bit(0, &printing))
+	if (!printable)
+		return;
+	if (!spin_trylock(&printing_lock))
 		return;
 
 	if (kmsg_redirect && vc_cons_allocated(kmsg_redirect - 1))

@@ -2481,7 +2483,7 @@ static void vt_console_print(struct cons
 	notify_update(vc);
 
 quit:
-	clear_bit(0, &printing);
+	spin_unlock(&printing_lock);
 }
 
 static struct tty_driver *vt_console_device(struct console *c, int *index)