linux-kernel - Re: [tip:x86/urgent] x86/mce: Fix CMCI preemption bugs

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Date:	Fri, 18 Apr 2014 10:07:16 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Owen Kibel <qmewlo@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Josh Boyer <jwboyer@...oraproject.org>,
	"Luck, Tony" <tony.luck@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"hpa@...or.com" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"atodorov@...hat.com" <atodorov@...hat.com>,
	"gong.chen@...ux.intel.com" <gong.chen@...ux.intel.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>
Subject: Re: [tip:x86/urgent] x86/mce: Fix CMCI preemption bugs


* Borislav Petkov <bp@...en8.de> wrote:

> On Thu, Apr 17, 2014 at 11:30:12PM +0200, Borislav Petkov wrote:
> > This is most likely unrelated and is caused by the preemption checks
> > added to __this_cpu_* in 188a81409ff7. If you'd like to debug this
> > further, please send a full dmesg:
> > 
> > dmesg > dmesg.log
> > 
> > Privately is fine too.
> 
> Ok, thanks for the dmesg. Replying to the thread with everybody:
> 
> The splat Owen is seeing is the same as this one at the beginning of
> this thread here:
> 
> http://lkml.kernel.org/r/8761m7lm3j.fsf@canonical.com
> 
> which has a viable fix. Btw, those two splats happen on HP notebooks.
> 
> Ok, good, I think we're all solved. Phew :-)
> 
> Thanks to all for their help.

Okay, so AFAICS the fix in x86/urgent isn't wrong functionally, it's 
just that the changelog incorrectly claims the raw-spinlock use is a 
bug causing a problem here.

Still that raw spinlock is bogus and might be hiding other problems, 
so we can keep the x86/urgent change (ea431643d6c3) as-is and I'll get 
it to Linus later today ...

Thanks,

	Ingo
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