linux-kernel - Re: [Bug 11388] New: 2.6.27-rc3 warns about MTRR range; only 3 of 16gb of memory is usable

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Message-ID: <20080826083534.GH10646@hoblitt.com>
Date:	Mon, 25 Aug 2008 22:35:34 -1000
From:	Joshua Hoblitt <j_kernel@...litt.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Yinghai Lu <yhlu.kernel@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	bugme-daemon@...zilla.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Bug 11388] New: 2.6.27-rc3 warns about MTRR range; only 3 of
	16gb of memory is usable

On Sat, Aug 23, 2008 at 12:43:11PM +0200, Ingo Molnar wrote:
> 
> * Yinghai Lu <yhlu.kernel@...il.com> wrote:
> 
> > On Fri, Aug 22, 2008 at 5:22 PM, Joshua Hoblitt <j_kernel@...litt.com> wrote:
> > > I've confirmed that the boards in these systems are Tyan Tempest 
> > > i5400PW (S5397)s.  We've discovered a workload that will deadlock 
> > > the system under both 2.6.24.2 and -tip kernel with the mtrr masking 
> > > patch.  The only thing unusual about this workload is that one of 
> > > the binaries in it constantly segvs...  Is it possible that these 
> > > deadlocks (no kernel oops on console) are caused by MSR setup 
> > > wierdness or is it likely unrelated?
> > 
> > could be other problem.
> > 
> > cpu should be smarter enough to understand the missing bits in mask. 
> > at least amd cpu. remember that we didn't set mask bits to 40bits with 
> > opteron with LinuxBIOS, and everything still works well.
> 
> yeah. Is the deadlock debuggable? (does nmi_watchdog=1 produce anything 
> useful, or does the enabling of CONFIG_PROVE_LOCKING=y show anything 
> weird in the syslog during light, non-deadlocking use of this workload?)

Enabling the nmi_watchdog doesn't produce anything at all (I double
checked the .config... it should be working).  Rebuilding with
PROVE_LOCKING seems to have prevented the deadlock.  It used to take
30-45 mins to lock the system up under heavy load and we're going on 6
hours here with no issues.  Absolutely nothing in the dmesg.  Ugh.  Any
other suggestions?  How bad is it to leave PROVE_LOCKING enabled?

-J

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