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Message-ID: <cd73a99e0911301215i7a61b468w3b49325bd1fda3ac@mail.gmail.com>
Date: Mon, 30 Nov 2009 22:15:38 +0200
From: Andrew Victor <avictor.za@...il.com>
To: Russell King - ARM Linux <linux@....linux.org.uk>
Cc: Alan Cox <alan@...rguk.ukuu.org.uk>,
David Brownell <dbrownell@...rs.sourceforge.net>,
Eric Miao <eric.y.miao@...il.com>,
Peter Zijlstra <peterz@...radead.org>,
John Stultz <johnstul@...ibm.com>,
Rusty Russell <rusty@...tcorp.com.au>,
Jamie Lokier <jamie@...reable.org>,
LKML <linux-kernel@...r.kernel.org>,
Remy Bohmer <linux@...mer.net>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Hugh Dickins <hugh.dickins@...cali.co.uk>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Ingo Molnar <mingo@...e.hu>,
Andrea Gallo <andrea.gallo@...ricsson.com>,
Uwe Kleine-König
<u.kleine-koenig@...gutronix.de>,
Thomas Gleixner <tglx@...utronix.de>,
Nicolas Pitre <nico@...vell.com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-arm-kernel@...ts.infradead.org
Subject: Re: Get rid of IRQF_DISABLED - (was [PATCH] genirq: warn about
IRQF_SHARED|IRQF_DISABLED)
hi,
> There is hardware out there (AT91) where
> the timer interrupt is shared with other peripherals, and you end
> up with a mixture of irqs-disabled and irqs-enabled handlers sharing
> the same interrupt.
For the AT91 case I don't think this shouldn't matter.
The AT91's have a priority-level interrupt controller, so:
1. a lower-priority interrupt won't interrupt a higher-priority
2. shared interrupts cannot interrupt each other until irq_finish()
is called (a write to AIC_EOICR)
Since the Timer, DBGU serial port (and other system peripherals) are
on the same priority level they cannot interrupt each other.
(ie, basically as-if always irqs-disabled).
The case of irqs-enabled does means that a higher-priority interrupt
could interrupt [*], but it's not a shared-IRQ in that case.
([*] The system peripherals have the highest priority by default, so
the user would need to override the defaults for this to occur)
Regards,
Andrew Victor
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