linux-kernel - [ 064/184] serial: 8250, increase PASS

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Message-Id: <20130604172132.959690964@1wt.eu>
Date:	Tue, 04 Jun 2013 19:22:34 +0200
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Jiri Slaby <jirislaby@...il.com>, Alan Cox <alan@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Ram Gupta <ram.gupta5@...il.com>, Willy Tarreau <w@....eu>
Subject: [ 064/184] serial: 8250, increase PASS_LIMIT

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

From: Jiri Slaby <jirislaby@...il.com>

With virtual machines like qemu, it's pretty common to see "too much
work for irq4" messages nowadays. This happens when a bunch of output
is printed on the emulated serial console. This is caused by too low
PASS_LIMIT. When ISR loops more than the limit, it spits the message.

I've been using a kernel with doubled the limit and I couldn't see no
problems. Maybe it's time to get rid of the message now?

[2.6.32: background info from Ram Gupta]

> I need a patch for serial driver that increases PASS_LIMIT merged in
> 3.1. I am using 2.6.32 kernel which experiences kernel panic
> occasionally. It will be great if you can backport to 2.6.32 and 3.0
> kernel. The commit ID is e7328ae1  serial: 8250, increase PASS_LIMIT

Signed-off-by: Jiri Slaby <jirislaby@...il.com>
Cc: Alan Cox <alan@...ux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
(cherry picked from commit e7328ae1848966181a7ac47e8ae6cddbd2cf55f3)
Cc: Ram Gupta <ram.gupta5@...il.com>
Signed-off-by: Willy Tarreau <w@....eu>
---
 drivers/serial/8250.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 6a451e8..12e1e9e 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -81,7 +81,7 @@ static unsigned int skip_txen_test; /* force skip of txen test at init time */
 #define DEBUG_INTR(fmt...)	do { } while (0)
 #endif
 
-#define PASS_LIMIT	256
+#define PASS_LIMIT	512
 
 #define BOTH_EMPTY 	(UART_LSR_TEMT | UART_LSR_THRE)
 
-- 
1.7.12.2.21.g234cd45.dirty



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