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

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Message-ID: <20140417100944.GG11096@twins.programming.kicks-ass.net>
Date:	Thu, 17 Apr 2014 12:09:44 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	mingo@...nel.org, hpa@...or.com, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, atodorov@...hat.com,
	tony.luck@...el.com, gong.chen@...ux.intel.com, bp@...en8.de,
	jwboyer@...oraproject.org, qmewlo@...il.com, tglx@...utronix.de
Cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/urgent] x86/mce: Fix CMCI preemption bugs

On Thu, Apr 17, 2014 at 02:57:54AM -0700, tip-bot for Ingo Molnar wrote:
> Commit-ID:  ea431643d6c38728195e2c456801c3ef66bb9991
> Gitweb:     http://git.kernel.org/tip/ea431643d6c38728195e2c456801c3ef66bb9991
> Author:     Ingo Molnar <mingo@...nel.org>
> AuthorDate: Thu, 17 Apr 2014 10:25:53 +0200
> Committer:  Ingo Molnar <mingo@...nel.org>
> CommitDate: Thu, 17 Apr 2014 10:28:42 +0200
> 
> x86/mce: Fix CMCI preemption bugs
> 
> The following commit:
> 
>   27f6c573e0f7 ("x86, CMCI: Add proper detection of end of CMCI storms")
> 
> Added two preemption bugs:
> 
>  - machine_check_poll() does a get_cpu_var() without a matching
>    put_cpu_var(), which causes preemption imbalance and crashes upon
>    bootup.
> 
>  - it does percpu ops without disabling preemption. Preemption is not
>    disabled due to the mistaken use of a raw spinlock.

it is arch_spinlock that doesn't disable preemption. raw_spinlock
disables preemption just fine.
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