linux-kernel - Re: Another preempt folding issue?

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Date:	Tue, 25 Mar 2014 09:23:37 +0100
From:	Stefan Bader <stefan.bader@...onical.com>
To:	Paolo Bonzini <pbonzini@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
CC:	Borislav Petkov <bp@...en8.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	kvm@...r.kernel.org, Marcelo Tosatti <mtosatti@...hat.com>,
	MASAO TAKAHASHI <masao-takahashi@...no.co.jp>,
	Joerg Roedel <joro@...tes.org>
Subject: Re: Another preempt folding issue?

On 24.03.2014 18:39, Paolo Bonzini wrote:
> Il 20/02/2014 16:50, Peter Zijlstra ha scritto:
>>>>> > >> One thing I likely should do is to reinstall the exact same laptop
>>>>> with 64bit
>>>>> > >> kernel and userspace... maybe only 64bit kernel first... and make sure
>>>>> on my
>>>>> > >> side that this does not show up on 64bit, too. I took the word of
>>>>> reporters for
>>>>> > >> that (and the impression that otherwise many more people would have
>>>>> complained).
>>>> > >
>>>> > > Yeha, I'm going to try and install some 32bit userspace on a usb
>>>> > > harddisk I've got and see if I can boot my Core2 laptop from that to try
>>>> > > and reproduce.
>>>> > >
>>>> > > But all that is probably going to be Monday :/
>>>> > >
>>> > *sigh* Already Thursday...
>>> >
>>> > Peter, did you get to reproduce this locally? Unfortunately I had some
>>> > interruption and have not more Information than on last Friday (which is that
>>> > the same hw but 64bit kernel does not show it).
>> I got side-tracked as well, someone reported crashes, which come above
>> weird behaviour :/
>>
> 
> Stefan, Peter, any news here?
> 
> Paolo

No, unfortunately not. :( I thought I had some idea as i386 seems to have soft
and hard irqs using a seperate stack and thought they maybe loose the process
flag there (x86_64 seems to always do that for soft irqs and if it does for hard
irqs it was hidden well enough for me not to see). But trial and error showed
showed no improvement when I made a copy of the original TIF_NEED_RSCHED before
executing on stack. So not really any further.
And then the usual distractions hit...

-Stefan


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