linux-kernel - Re: [PATCH v6 6/8] fsl-dma: use spin_lock_bh to instead of spin_lock

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Message-Id: <201208061157.17667.arnd@arndb.de>
Date:	Mon, 6 Aug 2012 11:57:17 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	qiang.liu@...escale.com
Cc:	linux-crypto@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	dan.j.williams@...el.com, linux-kernel@...r.kernel.org,
	dan.j.williams@...il.com, vinod.koul@...el.com,
	kim.phillips@...escale.com, herbert@...dor.hengli.com.au,
	davem@...emloft.net, gregkh@...uxfoundation.org,
	Li Yang <leoli@...escale.com>, Timur Tabi <timur@...escale.com>
Subject: Re: [PATCH v6 6/8] fsl-dma: use spin_lock_bh to instead of spin_lock_irqsave

On Monday 06 August 2012, qiang.liu@...escale.com wrote:
> 
> From: Qiang Liu <qiang.liu@...escale.com>
> 
> The use of spin_lock_irqsave() is a stronger locking mechanism than is
> required throughout the driver. The minimum locking required should be
> used instead. Interrupts will be turned off and context will be saved,
> there is needless to use irqsave.
> 
> Change all instances of spin_lock_irqsave() to spin_lock_bh().
> All manipulation of protected fields is done using tasklet context or
> weaker, which makes spin_lock_bh() the correct choice.
> 
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Dan Williams <dan.j.williams@...il.com>
> Cc: Vinod Koul <vinod.koul@...el.com>
> Cc: Li Yang <leoli@...escale.com>
> Cc: Timur Tabi <timur@...escale.com>
> Signed-off-by: Qiang Liu <qiang.liu@...escale.com>
> Acked-by: Ira W. Snyder <iws@...o.caltech.edu>

Acked-by: Arnd Bergmann <arnd@...db.de>

You could actually change the use of spin_lock_bh inside of the tasklet
function (dma_do_tasklet) do just spin_lock(), because softirqs are
already disabled there, but your version is also ok.
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