linux-kernel - Re: TTY loosing bytes ?

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Message-ID: <20091006141115.12ad22dd@lxorguk.ukuu.org.uk>
Date:	Tue, 6 Oct 2009 14:11:15 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	felipe.balbi@...ia.com
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"dbrownell@...rs.sourceforge.net" <dbrownell@...rs.sourceforge.net>
Subject: Re: TTY loosing bytes ?

> With the patch above I still get this messages but it still goes through
> since not receive_buf is returning the amount of bytes actually
> received. Then flush_to_ldisc() will retry those bytes on the next
> iteration. Maybe this is not the desired patch though ?
> 
> Thanks a lot for the comments Alan.

First guess try the following

n_tty: For some I/O patterns n_tty will lose bytes

From: Alan Cox <alan@...ux.intel.com>

Fix the obvious disagreement between the receive path and the receive room
logic.

Signed-off-by: Alan Cox <alan@...ux.intel.com>
---

 drivers/char/n_tty.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)


diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index 2e50f4d..27b28ca 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -95,6 +95,9 @@ static void n_tty_set_room(struct tty_struct *tty)
 	/* tty->read_cnt is not read locked ? */
 	int	left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
 
+	if (tty->real_raw)
+	        left = min(left, N_TTY_BUF_SIZE - tty->read_head - 1);
+
 	/*
 	 * If we are doing input canonicalization, and there are no
 	 * pending newlines, let characters through without limit, so
--
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