From: David Brownell <david-b@pacbell.net>
To: Alessandro Zummo <alessandro.zummo@towertech.it>
Cc: rtc-linux@googlegroups.com, Atsushi Nemoto <anemo@mba.ocn.ne.jp>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
hcegtvedt@atmel.com, vapier@gentoo.org,
rongkai.zhan@windriver.com, balajirrao@openmoko.org,
broonie@opensource.wolfsonmicro.com
Subject: Re: [rtc-linux] Re: [PATCH] rtc: Make rtc_update_irq callable with irqs enabled
Date: Thu, 23 Apr 2009 12:45:32 -0700 [thread overview]
Message-ID: <200904231245.33435.david-b@pacbell.net> (raw)
In-Reply-To: <20090423212639.7ba7cb0b@i1501.lan.towertech.it>
On Thursday 23 April 2009, Alessandro Zummo wrote:
>
> > If you're talking about a different patch, please forward...
>
> no patch, just theory.
>
> the question is, do we need IRQs disabled when
> calling rtc_update_irq?
If the spinlock is *ever* acquired with IRQs disabled,
it must *always* be acquired that way.
The typical use is ... from IRQ context, which will in
some cases mean IRQs disabled. QED.
> and if yes, why? to prevent what?
Consider: one context grabs spinlock with IRQs enabled.
IRQ arrives. That context tries to grab that same lock,
from the same CPU. ==> Self-deadlock.
next prev parent reply other threads:[~2009-04-23 19:45 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-06 16:50 [PATCH] rtc: Make rtc_update_irq callable with irqs enabled Atsushi Nemoto
2009-04-09 22:39 ` Andrew Morton
2009-04-09 22:58 ` Alessandro Zummo
2009-04-23 14:51 ` Atsushi Nemoto
2009-04-23 15:02 ` Alessandro Zummo
2009-04-23 15:07 ` [rtc-linux] " Mike Frysinger
[not found] ` <200904091627.15776.david-b@pacbell.net>
2009-04-23 15:29 ` Atsushi Nemoto
2009-04-23 15:46 ` Alessandro Zummo
2009-04-23 18:15 ` David Brownell
2009-04-23 18:27 ` [rtc-linux] " Alessandro Zummo
2009-04-23 19:02 ` David Brownell
2009-04-23 19:09 ` Alessandro Zummo
2009-04-23 19:25 ` David Brownell
2009-04-23 19:26 ` Alessandro Zummo
2009-04-23 19:45 ` David Brownell [this message]
2009-04-23 19:55 ` Alessandro Zummo
2009-04-24 9:31 ` David Brownell
2009-04-24 10:01 ` Alessandro Zummo
2009-04-24 11:10 ` David Brownell
2009-04-24 11:13 ` Alessandro Zummo
2009-04-24 16:48 ` Atsushi Nemoto
2009-04-24 17:06 ` Atsushi Nemoto
2009-04-24 19:41 ` Alessandro Zummo
2009-04-25 12:40 ` Atsushi Nemoto
2009-04-28 13:13 ` Hans-Christian Egtvedt
2009-04-28 15:56 ` Atsushi Nemoto
2009-04-23 15:37 ` Alessandro Zummo
2009-04-23 16:30 ` Mike Frysinger
2009-04-23 16:40 ` Alessandro Zummo
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