Re: New USB stack on FreeBSD w/Linux emulation layer coming
Pete Zaitcev <[email protected]>
| Newsgroups | gmane.linux.usb.devel |
|---|---|
| Organization | Red Hat, Inc. |
| Message-ID | <[email protected]> |
On Wed, 16 May 2007 11:38:47 -0400 (EDT), Alan Stern <[email protected]> wrote: > > > I have never, ever, seen USB stack deplete the atomic pool completely > > > either, if this is what you are talking about. So, you're quite right > > > about that. > > > > I was referring to the dma_pool allocations ... those don't need > > to be atomic. OHCI or EHCI tend to allocate a page or so for each > > type of descriptor seen by the hardware, and usually won't need > > more than that. UHCI uses more pages; TD-per-packet requirements > > from the hardware, ISTR (instead of multiple-pages-per-TD). > > If dma_pool allocation isn't atomic, does that mean it could block for > I/O? If yes, then it doesn't belong on the usb-storage I/O path. AFAIK, the definition is, GFP_NOIO can block, but it cannot wait for a writeout. If it cannot be satisfied without writing dirty data, it will fail. -- Pete ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel