Re: [BK-2.5] Update the generic DMA API to take GFP_ flags on

[James Bottomley]

[e-mail] said:
> Now what about the corollary, a platform that needs to sleep to setup
> the cpu mapings in a race-free manner? 

This one is the big bug bear.  The DMA-mapping.txt doc says 
pci_alloc_consistent "may be called in interrupt context".  Thus if the 
dma_alloc with GFP_ATOMIC uses the same code path, it should be safe.  
However, there are indications that pci_alloc_consistent wasn't interrupt safe 
on certain platforms (see other email re PA-RISC).

In any event, we're no worse off than we were with the pci_ API.  Passing in 
the flags will hopefully allow us to create GFP_ATOMIC safe paths in the arch 
implementations which look iffy.

James