Re: [PATCH v7 6/8] fsl-dma: use spin_lock_bh to instead of spin_lock_irqsave

[Dan Williams]

On Thu, Aug 9, 2012 at 1:23 AM,  <qiang.liu@xxxxxxxxxxxxx> wrote:
> From: Qiang Liu <qiang.liu@xxxxxxxxxxxxx>
>
> 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.

It seems you are coordinating fsl-dma copy and talitos xor operations.
 It looks like fsl-dma will be called through
talitos_process_pending()->dma_run_dependencies(), which is
potentially called in hard irq context.

This all comes back to the need to fix raid offload to manage the
channels explicitly rather than the current dependency chains.

--
Dan
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