linux-kernel - Re: [tip:x86/apic] x86/ioapic.c: unify ioapic_retrigger

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Date:	Wed, 22 Jul 2009 14:29:33 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	"mingo\@redhat.com" <mingo@...hat.com>,
	"hpa\@zytor.com" <hpa@...or.com>,
	"tglx\@linutronix.de" <tglx@...utronix.de>,
	Jeremy Fitzhardinge <Jeremy.Fitzhardinge@...rix.com>,
	Yinghai Lu <yinghai@...nel.org>
Subject: Re: [tip:x86/apic] x86/ioapic.c: unify ioapic_retrigger_irq()

Jeremy Fitzhardinge <jeremy@...p.org> writes:

> On 07/18/09 05:05, tip-bot for Jeremy Fitzhardinge wrote:
>> Commit-ID:  e25371d60cb06a44d7a32d7966ab9bfbeacb9390
>> Gitweb:     http://git.kernel.org/tip/e25371d60cb06a44d7a32d7966ab9bfbeacb9390
>> Author:     Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
>> AuthorDate: Mon, 8 Jun 2009 03:49:01 -0700
>> Committer:  Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
>> CommitDate: Tue, 14 Jul 2009 13:32:51 -0700
>>
>> x86/ioapic.c: unify ioapic_retrigger_irq()
>>
>> The 32 and 64-bit versions of ioapic_retrigger_irq() are identical
>> except the 64-bit one takes vector_lock.  vector_lock is defined and
>> used on 32-bit too, so just use a common ioapic_retrigger_irq().
>>   
>
> Having another look at this patch, the other difference is that the
> 32-bit version just does:
>
>     apic->send_IPI_self(irq_cfg(irq)->vector);
>
> whereas the 64-bit does:
>
>     apic->send_IPI_mask(cpumask_of(cpumask_first(cfg->domain)),
>     cfg->vector);
>
>
> Does 32-bit do the whole vector domain thing now?  Are these actually
> equivalent?  Sending to self seems like it should be more efficient.

It should.  I believe YH did that work when he merged the x86_64 and
i386 versions io_apic.c.  Sending to self is a problem if we retrigger
this from the wrong irq.

Eric
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