linux-kernel - Re: [RFC patch 0/5] genirq: add infrastructure for threaded interrupt handlers

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Message-ID: <alpine.LFD.1.10.0810020154570.5549@apollo.tec.linutronix.de>
Date:	Thu, 2 Oct 2008 01:58:20 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	mingo@...e.hu, benh@...nel.crashing.org, rostedt@...dmis.org,
	jonathan@...masters.org, sdietrich@...e.de
Subject: Re: [RFC patch 0/5] genirq: add infrastructure for threaded interrupt
 handlers

On Wed, 1 Oct 2008, Andrew Morton wrote:

> On Wed, 1 Oct 2008 16:29:50 -0700
> Arjan van de Ven <arjan@...radead.org> wrote:
> 
> > On Wed, 1 Oct 2008 16:23:33 -0700
> > Andrew Morton <akpm@...ux-foundation.org> wrote:
> > 
> > > 
> > > I'm a bit surprised to see that there is no facility for per-cpu
> > > interrupt threads?
> > > 
> > 
> > per handler is the right approach (that way, if one dies, all other
> > interrupts will likely keep working)
> > 
> > now.. normally an interrupt only goes to one cpu, so effectively it is
> > per cpu already anyway
> 
> Yes, if a) the thread was asleep when it was woken up and b) if the
> scheduler does the right thing and wakes the thread on the CPU which
> called wake_up().
> 
> The ongoing sagas of tbench/mysql/volanomark regressions make me think
> that any behaviour which we "expect" of the scheduler should be
> triple-checked daily :(

Yup. I missed that detail when I dusted off the moldy patches. 

Of course we need to pin the thread to the affinity mask of the
hardware interrupt.

/me goes back to do home work :)

Thanks,

	tglx
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