On Thu, Jan 21, 2016 at 03:18:48PM +0100, Oliver Neukum wrote: > Quting the relevant thread: > > > In fact, I suspect the locking added by the kernel 3.13 commit for > > read_descriptors() is invalid because read_descriptors() performs no USB > > activity; read_descriptors() just reads information from an allocated > > memory structure. This structure is protected as the structure is > > existing before and after the sysfs vfs descriptors entry is created or > > destroyed. > > You're right. For some reason I thought that usb_deauthorize_device() > would destroy the rawdescriptor structures (as mentioned in that > commit's Changelog), but it doesn't. The locking in read_descriptors() > is unnecessary. > > > The information is only written at the time of enumeration > > and does not change. At least that is my understanding. > > > > It is noted that in our testing of kernel 3.8 on ARM, that sysfs > > read_descriptors() was non-blocking because the kernel 3.13 comment was > > not there. > > > > The pre-kernel 3.13 sysfs read_descriptors() seemed to work OK. > > > > Proposal: > > ========= > > > > Remove the usb_lock_device(udev) and usb_unlock_device(udev) from > > devices/usb/core/sysfs.c in read_descriptors() that was added by the > > kernel 3.13 commit > > "232275a USB: fix substandard locking for the sysfs files" > > > > Any comments to this proposal ? > > It seems okay to me. Please submit a patch. > > So this removes the locking making the point about -EINTR in > the first path moot. I don't understand, should I drop this patch? Should I drop the first patch? confused, greg k-h -- 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
