Re: DMA APIs gumble grumble

[David Miller <davem@davemloft.net>]

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Fri, 10 Nov 2006 13:55:27 +1100

> > pci_alloc_consistent() is not allowed from atomic contexts.
> 
> Yes, but some drivers did it anyway, though I can't remember under which
> circumstances (IDE probe possibly ? It's a usual culprit for that sort
> of thing). This is why most implementations use GFP_ATOMIC (including
> sparc64 :-)

Ok, I see.

> Oh well, I have no problem with leaving sparc32 do GFP_KERNEL indeed, I
> can't remember for sure the reason why we have most architectures do
> GFP_ATOMIC, but it probably never hit sparc32.

I wish sparc32 hadn't used alloc_resource() as a poor-man's bitmap
allocator to keep track of IOMMU mappings.  That's where the
GFP_KERNEL requirement comes from.

Just use GFP_KERNEL for now, and someone might find the strength
to remove this problem some day :-)