From: Linus Torvalds <torvalds@osdl.org>
For testing, a patch like this might get rid of the problem by hiding the
race (but for all I know, gcc ends up re-loading it anyway) - you might
want to check the disassembly.
However, this patch is just for testing, to verify that your problem
really is that particular race. It's not a proper fix.
I suspect that pty's should always lock each others line disciplines too,
not just their "own" side.
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/drivers/char/pty.c | 6 ++++--
1 files changed, 4 insertions(+), 2 deletions(-)
diff -puN drivers/char/pty.c~pty-oops-fix drivers/char/pty.c
--- 25/drivers/char/pty.c~pty-oops-fix Thu Jan 27 16:36:38 2005
+++ 25-akpm/drivers/char/pty.c Thu Jan 27 16:36:38 2005
@@ -149,13 +149,15 @@ static int pty_write_room(struct tty_str
static int pty_chars_in_buffer(struct tty_struct *tty)
{
struct tty_struct *to = tty->link;
+ ssize_t (*chars_in_buffer)(struct tty_struct *);
int count;
- if (!to || !to->ldisc.chars_in_buffer)
+ /* We should get the line discipline lock for "tty->link" */
+ if (!to || !(chars_in_buffer = to->ldisc.chars_in_buffer))
return 0;
/* The ldisc must report 0 if no characters available to be read */
- count = to->ldisc.chars_in_buffer(to);
+ count = chars_in_buffer(to);
if (tty->driver->subtype == PTY_TYPE_SLAVE) return count;
_