Messages in this thread | | | Date | Tue, 17 Apr 2012 14:18:04 -0400 | From | KOSAKI Motohiro <> | Subject | Re: [PATCH 4/4] ARM: remove consistent dma region and use common vmalloc range for dma allocations |
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(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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