From: Alan Stern
> On Thu, 9 Jan 2014, David Laight wrote:
>
> > > From: Sarah Sharp
> > > Currently prepare_ring() returns -ENOMEM if the urb won't fit into a
> > > single ring segment. usb_sg_wait() treats this error as a temporary
> > > condition and will keep retrying until something else goes wrong.
> >
> > Even if it were a temporary condition then an immediate retry
> > is rather pointless.
> > Retry after a slight delay might make some sense.
>
> There is a yield(). It could be changed to something longer.
Will yield allow low priority processes to run?
> > Of course, if this is the pagedaemon trying to write out
> > pages in order to generate some free kernel memory all is lost
> > as soon as the usb subsystem need to allocate memory in order
> > to perform a transfer.
>
> That never happens, because all memory allocation requests on the
> storage I/O pathway are done using GFP_NOIO.
Picking hairs - not the ones in the xhci driver if, for example,
it has to extend the rings.
David
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