linux-kernel - RE: [RFC 0/4] ARM: dma-mapping: IOMMU atomic allocation

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Date:	Wed, 22 Aug 2012 14:04:26 +0200
From:	Marek Szyprowski <m.szyprowski@...sung.com>
To:	'Hiroshi Doyu' <hdoyu@...dia.com>
Cc:	linux-arm-kernel@...ts.infradead.org,
	linaro-mm-sig@...ts.linaro.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, kyungmin.park@...sung.com,
	arnd@...db.de, linux@....linux.org.uk, chunsang.jeong@...aro.org,
	'Krishna Reddy' <vdumpa@...dia.com>, konrad.wilk@...cle.com,
	subashrp@...il.com, minchan@...nel.org
Subject: RE: [RFC 0/4] ARM: dma-mapping: IOMMU atomic allocation

Hi Hiroshi,

On Wednesday, August 22, 2012 12:20 PM Hiroshi Doyu wrote:

> The commit e9da6e9 "ARM: dma-mapping: remove custom consistent dma
> region" breaks the compatibility with existing drivers. This causes
> the following kernel oops(*1). That driver has called dma_pool_alloc()
> to allocate memory from the interrupt context, and it hits
> BUG_ON(in_interrpt()) in "get_vm_area_caller()". This patch seris
> fixes this problem with making use of the pre-allocate atomic memory
> pool which DMA is using in the same way as DMA does now.
> 
> Any comment would be really appreciated.

I was working on the similar patches, but You were faster. ;-)

Basically the patch no 1 and 2 are fine, but I don't like the changes proposed in 
patch 3 and 4. You should not alter the attributes provided by the user nor make any
assumptions that such attributes has been provided - drivers are allowed to call 
dma_alloc_attrs() directly. Please rework your patches to avoid such approach.

Best regards
-- 
Marek Szyprowski
Samsung Poland R&D Center



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