[linuxppc-release] [PATCH v3 4/4] fsl-dma: use spin_lock_bh to instead of spin_lock_irqsave

[Liu Qiang-B32616]

> -----Original Message-----
> From: Tabi Timur-B04825
> Sent: Monday, July 16, 2012 10:25 PM
> To: Liu Qiang-B32616
> Cc: linux-crypto at vger.kernel.org; linuxppc-dev at lists.ozlabs.org; Vinod
> Koul; herbert at gondor.hengli.com.au; Dan Williams; Li Yang-R58472;
> davem at davemloft.net
> Subject: Re: [linuxppc-release] [PATCH v3 4/4] fsl-dma: use spin_lock_bh
> to instead of spin_lock_irqsave
> 
> Qiang Liu wrote:
> > Use spin_lock_bh to instead of spin_lock_irqsave for improving
> performance.
> 
> You forgot to include the evidence that performance has improved, as well
> as an explanation why it's okay to use spin_lock_bh, and why it's faster.
>   I told you to respin the patch with that information in the patch
> description.
I attached the test result in v3 0/4, performance is improved by 2%.
For my understanding, there is not any place to access descriptor lists
in fsl-dma interrupt service handler except its tasklet, spin_lock_bh()
is born for this. Interrupts will be turned off and context will be save in
irqsave, there is needless to use irqsave in our case. You can refer to the
implement of mv_xor.c or ioap-adma.c.
If you think my explanation is ok, I can add it in the patch.
Thanks.

> 
> --
> Timur Tabi
> Linux kernel developer at Freescale