linux-kernel - Re: [RFC,PATCH 1/2] Add a common struct clk

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Date:	Mon, 14 Jun 2010 19:22:58 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Lothar Waßmann <LW@...O-electronics.de>
Cc:	Jeremy Kerr <jeremy.kerr@...onical.com>,
	Ben Dooks <ben-linux@...ff.org>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Subject: Re: [RFC,PATCH 1/2] Add a common struct clk

On Mon, 2010-06-14 at 08:39 +0200, Lothar Waßmann wrote:
> All implementations so far use spin_lock_irq_save()!

Nothing prevents your implementation to be a tad smarter.

> How would you be able to sleep with a mutex held?
> If you hold a lock you must not sleep, no matter what sort of lock it
> is. 

You can perfectly sleep with a mutex held. You -do- have to be careful
of course to ensure you aren't going to do silly thing like re-enter and
try to take it twice, or A->B B->A deadlocks, but in the typical case of
wanting to use a msleep rather than udelay, it works very well :-)

Cheers,
Ben.


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