From: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
To: Minchan Kim <minchan@kernel.org>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Rik van Riel <riel@redhat.com>, Hugh Dickins <hughd@google.com>,
Mel Gorman <mgorman@suse.de>,
Johannes Weiner <hannes@cmpxchg.org>,
Marek Szyprowski <m.szyprowski@samsung.com>,
linux-arm-kernel@lists.infradead.org,
linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
Kyungmin Park <kyungmin.park@samsung.com>,
Arnd Bergmann <arnd@arndb.de>,
Chunsang Jeong <chunsang.jeong@linaro.org>,
Krishna Reddy <vdumpa@nvidia.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Hiroshi Doyu <hdoyu@nvidia.com>,
Subash Patel <subashrp@gmail.com>,
kosaki.motohiro@gmail.com
Subject: Re: [PATCH 4/4] ARM: remove consistent dma region and use common vmalloc range for dma allocations
Date: Tue, 17 Apr 2012 14:18:04 -0400 [thread overview]
Message-ID: <4F8DB3DC.7000602@gmail.com> (raw)
In-Reply-To: <4F8B76B9.1060505@kernel.org>
(4/15/12 9:32 PM), Minchan Kim wrote:
> On 04/14/2012 03:38 AM, Russell King - ARM Linux wrote:
>> On Fri, Apr 13, 2012 at 04:05:50PM +0200, Marek Szyprowski wrote:
>>> This patch changes dma-mapping subsystem to use generic vmalloc areas
>>> for all consistent dma allocations. This increases the total size limit
>>> of the consistent allocations and removes platform hacks and a lot of
>>> duplicated code.
>>
>> NAK. I don't think you appreciate the contexts from which the dma coherent
>> code can be called from, and the reason why we pre-allocate the page
>> tables (so that IRQ-based allocations work.)
>>
>> The vmalloc region doesn't allow that because page tables are allocated
>> using GFP_KERNEL not GFP_ATOMIC.
>>
>> Sorry.
>>
>
> Off-topic.
>
> I don't know why vmalloc functions have gfp_t argument.
> As Russel pointed out, we allocates page tables with GFP_KERNEL regardless of gfp_t passed.
> It means gfp_t passed is useless.
> I see there are many cases calling __vmalloc with GFP_NOFS, even GFP_ATOMIC. Then, it could end up deadlocking in reclaim context or schedule bug.
> I'm not sure why we can't see such bugs until now.
> If I didn't miss something, Shouldn't we fix it?
I believe it should be fixed. of course. :)
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next prev parent reply other threads:[~2012-04-17 18:18 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-13 14:05 [PATCH 0/4] ARM: replace custom consistent dma region with vmalloc Marek Szyprowski
2012-04-13 14:05 ` [PATCH 1/4] mm: vmalloc: use const void * for caller argument Marek Szyprowski
2012-04-13 14:05 ` [PATCH 2/4] mm: vmalloc: export find_vm_area() function Marek Szyprowski
2012-04-13 14:05 ` [PATCH 3/4] mm: vmalloc: add VM_DMA flag to indicate areas used by dma-mapping framework Marek Szyprowski
2012-04-13 14:05 ` [PATCH 4/4] ARM: remove consistent dma region and use common vmalloc range for dma allocations Marek Szyprowski
2012-04-13 18:38 ` Russell King - ARM Linux
2012-04-16 1:32 ` Minchan Kim
2012-04-17 18:18 ` KOSAKI Motohiro [this message]
2012-04-23 12:02 ` [Linaro-mm-sig] [PATCH 0/4] ARM: replace custom consistent dma region with vmalloc Abhinav Kochhar
2012-04-23 20:58 ` Daniel Vetter
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