linux-kernel - Re: [PATCH] 2.6.18-rt7: PowerPC: fix breakage in threaded fasteoi type IRQ handlers

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Message-ID: <20061120172642.GA8683@elte.hu>
Date:	Mon, 20 Nov 2006 18:26:42 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Sergei Shtylyov <sshtylyov@...mvista.com>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
	dwalker@...sta.com
Subject: Re: [PATCH] 2.6.18-rt7: PowerPC: fix breakage in threaded fasteoi type IRQ handlers


* Sergei Shtylyov <sshtylyov@...mvista.com> wrote:

> Hello.
> 
> Ingo Molnar wrote:
> 
> >>>on PPC64, 'get the vector' initiates an ACK as well - is that done 
> >>>before handle_irq() is done?
> 
> >>  Exactly. How else do_IRQ() would know the vector?
> 
> >the reason i'm asking is that in this case masking is a bit late at this 
> >point and there's a chance for a repeat interrupt.
> 
>    How's that? Acknowledge != EOI on OpenPIC (as well as 8259). 
> Acknoledging sets the bit in the in-service register preventing all 
> the interrupts with same or lower prioriry from being accepted.

ah, ok. The x86 APIC does that automatically, and only an EOI has to be 
passed. So i guess we are in wild agreement ;)

i'm hacking up something now to see whether it makes sense to introduce 
a central threaded flow type, or whether it's better the branch off the 
current flow types (as the code does it right now).

	Ingo
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