linux-kernel - Re: [rtc-linux] Re: [PATCH] rtc: Make rtc_update

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Message-ID: <20090428151353.0c15c5fc@hcegtvedt.norway.atmel.com>
Date:	Tue, 28 Apr 2009 15:13:53 +0200
From:	Hans-Christian Egtvedt <hans-christian.egtvedt@...el.com>
To:	Atsushi Nemoto <anemo@....ocn.ne.jp>
Cc:	alessandro.zummo@...ertech.it, rtc-linux@...glegroups.com,
	david-b@...bell.net, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, hcegtvedt@...el.com,
	vapier@...too.org, rongkai.zhan@...driver.com,
	balajirrao@...nmoko.org, broonie@...nsource.wolfsonmicro.com
Subject: Re: [rtc-linux] Re: [PATCH] rtc: Make rtc_update_irq callable with
 irqs enabled

On Sat, 25 Apr 2009 02:06:12 +0900 (JST)
Atsushi Nemoto <anemo@....ocn.ne.jp> wrote:

> On Sat, 25 Apr 2009 01:48:50 +0900 (JST), Atsushi Nemoto
> <anemo@....ocn.ne.jp> wrote:
> > Here is a possible example:
> > 
> > 1. RTC alarm interrupt handler takes rtc->irq_lock by spin_lock()
> > 2. A timer interrupt handler calls rtc_uie_timer() for UIE emulation
> > 3. rtc_uie_timer() waits on rtc->irq_lock .... deadlock!
> 
> Oops, this is wrong.  This deadlock cannot happen since
> rtc_uie_timer() will be called in bh (softirq) context, not interrupt
> context.
> 
> Anyway, I just posted updated patch.  Please take a look.  Thanks.
> 

AVR32 has interrupts disabled during the interrupt handler, so AFAICT
the rtc-at32ap700x.c should be fine.

-- 
Best regards,
Hans-Christian Egtvedt
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