linux-kernel - RE: hangs in verify_pmtmr

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Message-ID: <3E5A0FA7E9CA944F9D5414FEC6C712205DC2A819@ORSMSX106.amr.corp.intel.com>
Date:	Wed, 3 Jun 2015 21:48:37 +0000
From:	"Yu, Fenghua" <fenghua.yu@...el.com>
To:	Dave Hansen <dave@...1.net>, LKML <linux-kernel@...r.kernel.org>,
	"John Stultz" <john.stultz@...aro.org>,
	the arch/x86 maintainers <x86@...nel.org>
Subject: RE: hangs in verify_pmtmr_rate()

> From: Dave Hansen [mailto:dave@...1.net]
> Sent: Wednesday, June 03, 2015 12:55 PM
> To: LKML; Yu, Fenghua; John Stultz; the arch/x86 maintainers
> Subject: hangs in verify_pmtmr_rate()
> 
> 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?

Latest 4.1.0-rc5 defconfig boots fine without "pmtmr=0" on my machine which is same kind as Dave's.

I always give "hpet=disable" on this machine to w/a a known hw issue.

Thanks.

-Fenghua