linux-kernel - Re: x86: Inconsistent xAPIC synchronization in arch_irq_work

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Message-ID: <20140123191140.GV11314@laptop.programming.kicks-ass.net>
Date:	Thu, 23 Jan 2014 20:11:40 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Jan Kiszka <jan.kiszka@...mens.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Huang Ying <ying.huang@...el.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: x86: Inconsistent xAPIC synchronization in arch_irq_work_raise?

On Thu, Jan 23, 2014 at 07:51:40PM +0100, Jan Kiszka wrote:
> Next we have x86's arch_irq_work_raise which does wait-write-wait,
> either by chance or in order to work around a missing atomicity of
> wait+write somewhere else. Preemption is off, interrupts remain on.

Note that arch_irq_work_raise() is 'special' in that its used from NMI
context, so no amount of interrupts disabling will serialize things.
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