linux-kernel - [PATCH 49/49] serial8250: ratelimit "too much work" error

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Date:	Fri, 22 Oct 2010 11:21:28 -0700
From:	Greg Kroah-Hartman <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org
Cc:	Daniel Drake <dsd@...top.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: [PATCH 49/49] serial8250: ratelimit "too much work" error

From: Daniel Drake <dsd@...top.org>

Running a serial console, if too many kernel messages are generated within
a short time causing a lot of serial I/O, the 8250 driver will generate
another kernel message reporting this, which just adds to the I/O. It has
a cascading effect and quickly results the system being brought to its knees
by a flood of "too much work" messages.

Ratelimit the error message to avoid this.

[akpm@...ux-foundation.org: use the superior printk_ratelimited()]
[akpm@...ux-foundation.org: printk_ratelimited() needs ratelimit.h]
Signed-off-by: Daniel Drake <dsd@...top.org>
Acked-by: Alan Cox <alan@...ux.intel.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 drivers/serial/8250.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 37f19a6..167c4a6 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -31,6 +31,7 @@
 #include <linux/delay.h>
 #include <linux/platform_device.h>
 #include <linux/tty.h>
+#include <linux/ratelimit.h>
 #include <linux/tty_flip.h>
 #include <linux/serial_reg.h>
 #include <linux/serial_core.h>
@@ -1600,8 +1601,8 @@ static irqreturn_t serial8250_interrupt(int irq, void *dev_id)
 
 		if (l == i->head && pass_counter++ > PASS_LIMIT) {
 			/* If we hit this, we're dead. */
-			printk(KERN_ERR "serial8250: too much work for "
-				"irq%d\n", irq);
+			printk_ratelimited(KERN_ERR
+				"serial8250: too much work for irq%d\n", irq);
 			break;
 		}
 	} while (l != end);
-- 
1.7.2

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