linux-kernel - Re: hangs in verify_pmtmr

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Date:	Wed, 3 Jun 2015 13:46:26 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Dave Hansen <dave@...1.net>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"Yu, Fenghua" <fenghua.yu@...el.com>,
	"the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: hangs in verify_pmtmr_rate()

On Wed, Jun 3, 2015 at 12:55 PM, Dave Hansen <dave@...1.net> wrote:
> I'm seeing boot hangs when trying to boot a 32-bit 4.1.0-rc5 kernel on
> some 64-bit CPUs (I'm not sure if it is a regression).  The NMI watchdog
> shows init_acpi_pm_clocksource() as the last thing in the backtrace,
> specifically verify_pmtmr_rate()'s I/O instructions.  It appears to be
> mach_countup()'s while loop that gets stuck.
>
> Booting with "pmtmr=0" works around this for me, as would unsetting
> CONFIG_X86_PM_TIMER I'd imagine.
>
> The hardware I'm doing this on is a bit wonky and I think the hpet is
> broken on it.
>
> Does this look like *really* broken hardware, or something that we
> should be detecting and able to recover from?

Hrm. Does this machine have a working PIT?

Does pit_calibrate_tsc() end up being used on this box to calibrate
the TSC (its similar logic, so it should get stuck in the same way),
or does it use a different method for tsc calibration?

thanks
-john
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