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

Joshua Hoblitt
2008-08-26T08:35:45Z

On Sat, Aug 23, 2008 at 12:43:11PM +0200, Ingo Molnar wrote:
>
> * Yinghai Lu <yhlu.kernel@gmail.com> wrote:
>
> > On Fri, Aug 22, 2008 at 5:22 PM, Joshua Hoblitt <j_kernel@hoblitt.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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