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

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Message-ID: <alpine.LFD.2.00.0909040753370.17375@eeepc.linux-foundation.org>
Date:	Fri, 4 Sep 2009 07:55:30 -1000 (HST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Mikael Pettersson <mikpe@...uu.se>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Alan Cox <alan@...ux.intel.com>, Greg KH <gregkh@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Subject: Re: [Bug #14015] pty regressed again, breaking expect and gcc's
 testsuite



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;
--
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