linux-kernel - Re: [RFC][PATCH] irq: support IRQ_NESTED_THREAD with non-threaded interrupt handlers

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Message-ID: <AANLkTimlSBEhl58CNuScKjxbqdTwTYgqo7vrHTcd1x9G@mail.gmail.com>
Date:	Sat, 5 Jun 2010 19:01:47 +0200
From:	Esben Haabendal <esbenhaabendal@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Marc Zyngier <maz@...terjones.org>,
	Esben Haabendal <eha@...edevelopment.dk>,
	linux-kernel@...r.kernel.org, mingo@...e.hu,
	joachim.eastwood@...ron.com
Subject: Re: [RFC][PATCH] irq: support IRQ_NESTED_THREAD with non-threaded 
	interrupt handlers

On Sat, Jun 5, 2010 at 5:33 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> On Sat, 5 Jun 2010, Marc Zyngier wrote:
>> You may want to give request_any_context_irq() a try (available since the
>> latest merge window). It still requires your driver to be changed, but it
>> should then work in both threaded and non-threaded cases.
>
> And it nicely annotates that somebody looked at the driver in
> question. That's the rule of least surprise and does not impose checks
> on the fast path.

What in particular should I be looking for in a driver before changing
from request_irq() to request_any_context_irq() ?

As for not checking in the fast path, it should be noted that this is "only"
in handle_nested_irq(), which is only used in few interupt controller
drivers, all of which I assume are generally not considered very "fast".

Unless all interrupt handlers should be rewritten to be able to in both
thread and interrupt context, I fail to se the conflict between the patch
proposed and the work being done on request_any_context_irq().

/Esben
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