Re: [PATCH v2] [watchdog] combine nmi_watchdog and softlockup

From: Frederic Weisbecker <fweisbec@gmail.com>
To: Don Zickus <dzickus@redhat.com>
Cc: mingo@elte.hu, peterz@infradead.org, gorcunov@gmail.com,
	aris@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] [watchdog] combine nmi_watchdog and softlockup
Date: Fri, 16 Apr 2010 18:24:19 +0200	[thread overview]
Message-ID: <20100416162417.GI5162@nowhere> (raw)
In-Reply-To: <20100416161401.GI15159@redhat.com>

On Fri, Apr 16, 2010 at 12:14:01PM -0400, Don Zickus wrote:
> 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; }

Ah right.

> 
> > 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 :-) ).

Ok :)