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Softdog enhancement to optionally invoke panic instead of reboot on timer expiry

PATCH RESEND In review Anithra P Janakiraman 2 participants 2 messages Mar 28, 2011 Watchdog device drivers

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Anithra P Janakiraman

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#0 lore raw

PATCH RESEND 1/1 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 <[email protected]>

Signed-off-by Anithra P J <[email protected]>
Reviewed-by WANG Cong <[email protected]>
---
 drivers/watchdog/softdog.c |   18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)
drivers/watchdog/softdog.c +15 -3
Index: 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;
 }
Acked-by on v1 1/1
#1 lore raw
Quoted 12 lines · On Mon, 28 Mar 2011 20:35:02 +0530 Anithra P Janakiraman…

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.

Looks sensible to me.

Acked-by Alan Cox <[email protected]>

Alan