linux-kernel - Re: [patch] x86, apic: use 0x20 for the IRQ_MOVE_CLEANUP

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Message-ID: <m1vdf57nel.fsf@fess.ebiederm.org>
Date:	Wed, 13 Jan 2010 12:36:18 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Suresh Siddha <suresh.b.siddha@...el.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Yinghai Lu <yinghai@...nel.org>,
	"Maciej W. Rozycki" <macro@...ux-mips.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [patch] x86, apic: use 0x20 for the IRQ_MOVE_CLEANUP_VECTOR instead of 0x1f

"H. Peter Anvin" <hpa@...or.com> writes:

> On 01/11/2010 05:52 PM, Eric W. Biederman wrote:
>> 
>> After having the documentation quoted at me.  I am having a distinct
>> memory of one piece of documentation saying:
>> "interrupts within a priority level can be delivered in any order"
>> 
>> So I am guessing there is not any ordering of interrupts in the same
>> priority level until they get to the local apic.
>> 
>
> There is no ordering of interrupts before they hit the local APIC, since
> the local APIC is what would serialize them...

The io apic serializes them, and sends them over either the 2-wire
bus or the front side bus.   How much serialization and prioritization
happens at that point I am not certain, but some certainly happens
before you get to the local apic.

Eric

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