[ 064/184] serial: 8250, increase PASS_LIMIT

From: Willy Tarreau
Date: Tue Jun 04 2013 - 19:19:32 EST

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


From: Jiri Slaby <jirislaby@xxxxxxxxx>

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@xxxxxxxxx>
Cc: Alan Cox <alan@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
(cherry picked from commit e7328ae1848966181a7ac47e8ae6cddbd2cf55f3)
Cc: Ram Gupta <ram.gupta5@xxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
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)

-#define PASS_LIMIT 256
+#define PASS_LIMIT 512



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