linux-kernel - Re: [PATCH v2] [watchdog] combine nmi

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Message-ID: <20100416161401.GI15159@redhat.com>
Date:	Fri, 16 Apr 2010 12:14:01 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	mingo@...e.hu, peterz@...radead.org, gorcunov@...il.com,
	aris@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] [watchdog] combine nmi_watchdog and softlockup

On Fri, Apr 16, 2010 at 05:32:12PM +0200, Frederic Weisbecker wrote:
> > I'll try to implement this.  Any objections if I combined hardlockup and
> > softlockup with per cpu watchdog_warn and have bit masks for HARDLOCKUP
> > and SOFTLOCKUP?  I hate to just waste per cpu space for this.
> 
> 
> 
> Hmm, a hardlockup can come in after a softlockup.

Let me re-explain what I meant.  It was meant to do double duty.  The
softlockup code only checks the SOFTLOCKUP bit and the hardlockup only
ever checks the HARDLOCKUP bit.

ie if get_cpu_var(watchdog_warn) && HARDLOCKUP { return; }

> Don't worry too much about memory: usually the more you have cpu,
> the more you have memory :)
> Plus this is debugging code, not something supposed to be enabled
> in production.

Well depends on your POV.  In RHEL we enable both NMI_WATCHDOG and
SOFTLOCKUP on production systems (and we have customers that are
thankful for that :-) ).

Cheers,
Don
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