linux-kernel - Re: [regression]: soft lockup in dmesg after suspend/resume

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Date:	Thu, 21 Jan 2010 07:18:05 -0800
From:	Greg KH <greg@...ah.com>
To:	ykzhao <yakui.zhao@...el.com>
Cc:	mingo@...e.hu, linux-kernel@...r.kernel.org, nanhai.zou@...el.com,
	venkatesh.pallipadi@...el.com
Subject: Re: [regression]: soft lockup in dmesg after suspend/resume

On Mon, Jan 04, 2010 at 01:36:50PM +0800, ykzhao wrote:
> Hi,
>    My box can work well before suspend/resume. But it will complain the
> following warning message after suspend/resume. 
>    >[1266874868.022103] Enabling non-boot CPUs ...
> [1266874868.022198] BUG: soft lockup - CPU#0 stuck for 0s! [kthreadd:2]
> 
>     At the same time after I add the boot option of "printk.time=1", I
> find that the log time is changed spontaneously from 76 to 1266874868.
>     > [   76.475266] CPU3 is down
> [   76.475312] Extended CMOS year: 2000
> [1266874868.020631] x86 PAT enabled: cpu 0, old 0x7040600070406, new
> 0x7010600070106
> [1266874868.021779] Back to C!
> [1266874868.022003] CPU0: Thermal LVT vector (0xfa) already installed
> [1266874868.022060] Extended CMOS year: 2000
> 
>     More detailed info can be found in the attached file of
> dmesg_after_origin.
> 
>    After I look at the source code, I find that on this box the TSC runs
> at constant rate with P/T states and does not stop in deep C-states. And
> then the sched_clock_stable is set to 1. In such case the TSC time is
> used directly in the function of sched_clock_cpu. 
>    
>    Then I do another test on this box, in which the clock_stable flag is
> saved/restored in course of suspend/resume(I add this by using per-cpu
> structure). When entering the suspended state, the clock_stable will be
> cleared. And when the system is resumed, the clock_stable will be set
> again. But unfortunately the soft lockup still exists. The file of
> dmesg_after_test2 is the dmesg log after I save/restore the clock_stable
> flag in course of suspend/resume.
> 
>    How about clearing the sched_clock_stable flag even when TSC doesn't
> stop in deep C-state?  From my test it seems that the TSC value is
> unknown after doing suspend/resume. 

I'm seeing this as well (Ingo, sorry for not searching more in the
archives before sending my other message.)

Any ideas on what I can do here?

Yes, the clock changes a bunch on resume, that's natural, we should
be able to handle this properly, right?

thanks,

greg k-h
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