Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote @ Tue, 21 Aug 2012 14:34:51 +0200:
> On Tue, Aug 21, 2012 at 02:22:35PM +0300, Hiroshi Doyu wrote:
> > The following "__get_vm_area_node()" can take gfp_mask, it means that
> > this function is expected to be called from atomic context, but why
> > it's _NOT_ allowed _ONLY_ from interrupt context?
>
> One reason is it takes read/write locks without using the IRQ safe
> versions for starters (vmap_area_lock and vmlist_lock). I don't see
> any other reasons in that bit of code though.
IIRC, if *_{irqsave,irqrestore} versions were introduced to protect
from IRQ context, could we remove this BUG_ON(in_interrupt()) in
__get_vm_area_node() at least? Or is it not encouraged from
performance POV?
It seems that the solution to allow IOMMU'able device driver to
allocate from ISR are:
(1) To provide the pre-allocate area like arm_dma_alloc() does,
or
(2) __get_vm_area_node() can be called from ISR.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href