linux-kernel - [RESEND] [PATCH] Softdog enhancement to optionally invoke panic instead of reboot on timer expiry

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Message-ID: <20110328203502.5d62fea4@linux.vnet.ibm.com>
Date:	Mon, 28 Mar 2011 20:35:02 +0530
From:	Anithra P Janakiraman <anithra@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	dave@...ux.vnet.ibm.com, xiyou.wangcong@...il.com,
	sugaken.r3@...il.com, alan@...rguk.ukuu.org.uk,
	akpm@...ux-foundation.org, vatsa@...ux.vnet.ibm.com,
	ananth@...ibm.com
Subject: [RESEND] [PATCH] Softdog enhancement to optionally invoke panic
 instead of reboot on timer expiry

Hi,

The patch is needed for determining the reason for failure when a
softdog timeout occurs. We use softdog to watch for critical
application failures and at the minimum a snapshot of the system would
help to determine the cause. In such a scenario the application could
fail but there isn't a softlockup as such, hence the detect softlockup
feature does not help. The patch below adds a module parameter
soft_panic which when set to 1 causes softdog to invoke panic instead
of reboot when the softdog timer expires. By invoking panic we execute
kdump if it is configured and the vmcore generated by kdump should
provide atleast a minimal idea of the reason for failure.

Thank You,
Regards,
Anithra. 

Patch:

Based on an original patch by Ken Sugawara <sugaken.r3@...il.com>
Signed-off-by: Anithra P J <anithra@...ux.vnet.ibm.com>
Reviewed-by: WANG Cong <xiyou.wangcong@...il.com>

---
 drivers/watchdog/softdog.c |   18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

Index: linux-2.6.38-rc1/drivers/watchdog/softdog.c
===================================================================
--- linux-2.6.38-rc1.orig/drivers/watchdog/softdog.c
+++ linux-2.6.38-rc1/drivers/watchdog/softdog.c
@@ -48,6 +48,7 @@
 #include <linux/init.h>
 #include <linux/jiffies.h>
 #include <linux/uaccess.h>
+#include <linux/kernel.h>
 
 #define PFX "SoftDog: "
 
@@ -75,6 +76,13 @@
 	"Softdog action, set to 1 to ignore reboots, 0 to reboot "
 					"(default depends on ONLY_TESTING)");
 
+
+static int soft_panic;
+
+module_param(soft_panic, int, 0);
+MODULE_PARM_DESC(soft_panic,
+	"Softdog action, set to 1 to panic, 0 to reboot (default 0)");
+
 /*
  *	Our timer
  */
@@ -98,7 +106,10 @@
 
 	if (soft_noboot)
 		printk(KERN_CRIT PFX "Triggered - Reboot ignored.\n");
-	else {
+	else if (soft_panic) {
+		printk(KERN_CRIT PFX "Initiating panic.\n");
+		panic("Software Watchdog Timer expired.");
+	} else {
 		printk(KERN_CRIT PFX "Initiating system reboot.\n");
 		emergency_restart();
 		printk(KERN_CRIT PFX "Reboot didn't ?????\n");
@@ -267,7 +278,8 @@
 };
 
 static char banner[] __initdata = KERN_INFO "Software Watchdog Timer: 0.07 "
-	"initialized. soft_noboot=%d soft_margin=%d sec (nowayout= %d)\n";
+	"initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d "
+	"(nowayout= %d)\n";
 
 static int __init watchdog_init(void)
 {
@@ -298,7 +310,7 @@
 		return ret;
 	}
 
-	printk(banner, soft_noboot, soft_margin, nowayout);
+	printk(banner, soft_noboot, soft_margin, soft_panic, nowayout);
 
 	return 0;
 }
--
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