On Wed, 6 May 2009 15:34:52 +0200 Oliver Neukum <oliver@xxxxxxxxxx> wrote: > Am Dienstag, 5. Mai 2009 19:22:53 schrieb Andrew Morton: > > On Tue, 5 May 2009 12:44:01 +0200 Oliver Neukum <oliver@xxxxxxxxxx> wrote: > > > > USB drivers are interface level yet some functions, reset and power > > > management, are on a device level. As it is unpredictable whether > > > a driver will share a device with a storage driver, all USB drivers as > > > far as these functions are concerned must be considered block device > > > drivers. That's the reason GFP_NOIO is so prevalent in USB. > > > > There must be some particular action which flips the thread of control > > from one state to the other. eg, taking of a lock. > > Basically assigning an interface to the storage or ub driver. That's hardly enough information for anyone to understand what you mean :( Oh well, doesn't matter. > > > > I wonder how hard it would be to add runtime debugging checks? If > > > > > > I'd prefer compile time checks. Ideally we'd annotate a function with an > > > attribute making the compiler barf if copy_to/from_user or an > > > inappropriate kmalloc is used. It can't be perfect due to function > > > pointers, but it would be a good start. > > > > I don't think that would have enough coverage - bugs in this area tend > > to come from calling some function which looks innocent, but which > > calls some function which calls some function which calls some function > > which uses GFP_KERNEL. > > > > And then there's stuff like "usb takes a mutex which is also taken by > > some other thread which does a GFP_KERNEL allocation while holding that > > mutex". > > Yes, but to catch that you'd have to teach lockdep about those functions > whose locks are dangerous to share with respect to memory allocation. > Is there another way to do that besides labelling dangerous methods? Adding lockdep annotation to the locks, I guess. Probably a new kind of annotation. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
