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

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Message-Id: <20090425.020612.92585418.anemo@mba.ocn.ne.jp>
Date:	Sat, 25 Apr 2009 02:06:12 +0900 (JST)
From:	Atsushi Nemoto <anemo@....ocn.ne.jp>
To:	alessandro.zummo@...ertech.it
Cc:	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 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.

---
Atsushi Nemoto
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