On Mon, 4 May 2009 16:01:51 +0200 Oliver Neukum <oliver@xxxxxxxxxx> wrote: > Am Montag, 4. Mai 2009 09:02:38 schrieb David Brownell: > > On Sunday 03 May 2009, Oliver Neukum wrote: > > > No. To make it plain. To me any use of memdup_user() in USB code > > > is a bad idea. I don't want to have to think about a new primitive. > > > > Unless it's incorrect to use that, I have to say that it > > makes more sense to use that utility than recreate it by > > open-coding... > > I want people to be forced to think about memory allocations. > We had endless trouble during 2.4 with storage deadlocking. > We simply need full control of this. > thou-shalt-use-GFP_NOFS is a very common pattern in many filesystems. And thou-shalt-use-GFP_NOIO is a very common pattern in block drivers. I wonder how hard it would be to add runtime debugging checks? If there are clearly identified transition points where (say) GFP_NOIO becomes required and unrequired then we could do something along the lines of current->disallowed_gfp_flags |= __GFP_IO; .... current->disallowed_gfp_flags &= ~__GFP_IO; and check (gfp_flags & current->disallowed_gfp_flags) in the various memory-allocation functions, and perhaps in the uaccess functions. Or possibly teach lockdep about it, although that seems inappropriate. Anyway. A little project for someone, perhaps. -- 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
