Re: [Bug #14015] pty regressed again, breaking expect and gcc's testsuite

[Linus Torvalds <torvalds@linux-foundation.org>]

On Fri, 4 Sep 2009, Linus Torvalds wrote:
> 
> How about something like this? It's way too anal - it says that we can 
> only write data if there's enough space to always push it all the way to 
> the receive buffer (including all the data that was already buffered up, 
> ie the "memory_used" part). But if it finally makes the problem go away, 
> we have another clue.

I forgot to actually include the patch. Duh.

And again - UNTESTED. Maybe this makes the buffering _too_ small (the 
'memory_used' thing is not really counted in bytes buffered, it's counted 
in how much buffer space we've allocated) and things break even worse and 
pty's don't work at all. But I think it might work.

		Linus

---
 drivers/char/pty.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/char/pty.c b/drivers/char/pty.c
index d083c73..139fa5a 100644
--- a/drivers/char/pty.c
+++ b/drivers/char/pty.c
@@ -91,7 +91,7 @@ static void pty_unthrottle(struct tty_struct *tty)
 
 static int pty_space(struct tty_struct *to)
 {
-	int n = 8192 - to->buf.memory_used;
+	int n = to->receive_room - to->buf.memory_used;
 	if (n < 0)
 		return 0;
 	return n;