From b0940003f25dd3d2c54c4879809a432a35197f54 Mon Sep 17 00:00:00 2001
From: Nick Piggin <npiggin@suse.de>
Date: Wed, 6 Feb 2008 01:37:04 -0800
Subject: [PATCH] vt: bitlock fix
vt is missing a memory barrier to close the critical section. Use a real
spinlock for this.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
drivers/char/vt.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index 7a5badfb7d846..367be91750611 100644
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -2400,13 +2400,15 @@ static void vt_console_print(struct console *co, const char *b, unsigned count)
{
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 console *co, const char *b, unsigned count)
notify_update(vc);
quit:
- clear_bit(0, &printing);
+ spin_unlock(&printing_lock);
}
static struct tty_driver *vt_console_device(struct console *c, int *index)
--
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