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

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Message-ID: <20140417152611.GD4321@pd.tnic>
Date:	Thu, 17 Apr 2014 17:26:11 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	"Luck, Tony" <tony.luck@...el.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...nel.org" <mingo@...nel.org>,
	"hpa@...or.com" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
	"atodorov@...hat.com" <atodorov@...hat.com>,
	"gong.chen@...ux.intel.com" <gong.chen@...ux.intel.com>,
	"jwboyer@...oraproject.org" <jwboyer@...oraproject.org>,
	"qmewlo@...il.com" <qmewlo@...il.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

On Thu, Apr 17, 2014 at 02:03:34PM +0000, Luck, Tony wrote:
> > Hohum, __raw_spin_lock_irqsave does preempt_disable(). And
> > machine_check_poll should be running in irq context so why would the
> > original issue happen?
> >
> >> kernel: [    7.341085] BUG: using __this_cpu_write() in preemptible [00000000] code: modprobe/546
> >
> > Unfortunately, I have only one line in a mail CCed to me.
> >
> > Color me confused.
> 
> Is this just the missing put_cpu() that Chen Gong already sent a patch for?

I'm not sure. There's some bug report floating around which contains the
"BUG" line above but I can't seem to find/get it.

I'll boot latest Linus tree on my SNB machine to check whether it
triggers here. Ingo says CONFIG_DEBUG_PREEMPT=y is causing it but this
is all hearsay stuff from where I'm standing...

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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