>As far as I can tell there's no problem with get_free_pages() (or >rather, alloc_pages()), except that we need to add GFP_ATOMIC to the >flags if we're in interrupt context. > >The problems are in get_vm_area() which does a kmalloc() without >GFP_ATOMIC and in map_page() which can sleep.
(Note do DaveM: this thread from linuxppc-embedded talks about out consistent_alloc() functions used to get non-cacheable DMA consistent memory for peripherials on the various non-PCI type busses you can find on such embedded CPUs) We can't rely on in_interrupt(). We can be called with a spinlock held or on the VM path. In those cases, we need GFP_ATOMIC but in_interrupt() won't be set. I would rather pass a gfp_mask argument to consistent_alloc. I know the pci_xxx version lacks that argument, I yet have to talk to DaveM about it, in the meantime, it should be implemented as calling consistent_alloc(..., GFP_ATOMIC). I want the gfp argument to be passed since some drivers will want a quite large pool to be allocated at insmod/kernel init time, and I want to let those drivers to be able to sleep while VM gets the pages back in this case instead of failing as they would probably do with a GFP_ATOMIC on a machine that have been running for some time. Ben. ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
