linux-kernel - Re: [BUG?] false positive in soft lockup detector while unlzma initramfs on slow cpu

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Date:	Wed, 30 Jan 2013 10:51:21 -0500
From:	Don Zickus <dzickus@...hat.com>
To:	anish kumar <anish198519851985@...il.com>
Cc:	Mike Lykov <combr@...dex.ru>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, linux-watchdog@...r.kernel.org,
	kirill@...temov.name
Subject: Re: [BUG?] false positive in soft lockup detector while unlzma
 initramfs on slow cpu

On Tue, Jan 29, 2013 at 10:48:27PM +0530, anish kumar wrote:
> Sorry for digressing from the topic but I think there is something wrong
> with my understanding or something wrong with the code.So I guess Don
> can clarify this.
> If I pass this below parameter during boot i.e. setting watchdog_enabled
> to zero.
> __setup("nowatchdog", nowatchdog_setup);
> 
> Now I use sysctl to enable the watchdog then wouldn't the below code
> will hinder enabling the watchdog?
> 
> static void watchdog_enable_all_cpus(void)
> {//snip
>         if (watchdog_disabled) {  /* this is zero ?? */
>                 watchdog_disabled = 0;
> //snip
> }
> 
> Should watchdog_disabled be set to 1?Or is it that we always disable the
> watchdog and then enable it?

It seems like a bug, so does something like this fix it?  There is
probably a better way to handle the internal representation of the
watchdog state (watchdog_disable) and the procfs version
(watchdog_enable), but I just can't think of something right now. :-(

Cheers,
Don


diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 75a2ab3..d287726 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -82,6 +82,7 @@ __setup("softlockup_panic=", softlockup_panic_setup);
 static int __init nowatchdog_setup(char *str)
 {
 	watchdog_enabled = 0;
+	watchdog_disabled =1;
 	return 1;
 }
 __setup("nowatchdog", nowatchdog_setup);
--
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