linux-kernel - Re: [PATCH 1/6] dmaengine/dw_dmac: Replace spin_lock

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Message-ID: <20110427072802.GG17290@n2100.arm.linux.org.uk>
Date:	Wed, 27 Apr 2011 08:28:02 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	viresh kumar <viresh.kumar@...com>
Cc:	"vinod.koul@...el.com" <vinod.koul@...el.com>,
	"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Armando VISCONTI <armando.visconti@...com>,
	Shiraz HASHIM <shiraz.hashim@...com>,
	amitgoel <amit.goel@...com>,
	"viresh.linux@...il.com" <viresh.linux@...il.com>,
	"jamie@...ieiles.com" <jamie@...ieiles.com>
Subject: Re: [PATCH 1/6] dmaengine/dw_dmac: Replace spin_lock_bh with
	irqsave variants

On Wed, Apr 27, 2011 at 11:29:49AM +0530, viresh kumar wrote:
> There are two kinds of locks taken in dw_dmac: spin_lock_bh and spin_lock.
> spin_lock_bh is taken from routines called from external drivers and spin_lock
> taken inside tasklet.
> For reasons mentioned earlier, spin_lock_bh has to be replaced with spin_lock_irqsave.
> 
> Now, Is simple spin_lock() sufficient inside tasklet?? As dma API's can be called
> from interrupt context (which will try to take spin_lock_irqsave).

Tasklets can be interrupted, so no.
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