On Wed, Aug 28, 2013 at 08:27:48AM -0700, Sarah Sharp wrote: > On Tue, Aug 27, 2013 at 05:41:19PM -0700, Greg KH wrote: > > On Mon, Aug 26, 2013 at 06:59:22PM -0700, Sarah Sharp wrote: > > > I attempted to replicate this bug with Ubuntu 12.04, but could not. I > > > used Ubuntu 12.04 on the same platform, with the same BIOS that the bug > > > was triggered on ChromeOS with. I also changed the USB sysfs settings > > > as described above, but still could not reproduce the bug under Ubuntu. > > > It may be that ChromeOS userspace triggers this bug through additional > > > settings. > > > > Did you test this on ChromeOS to determine that the patch fixes the bug? > > Yes, it does fix the bug. Great, I didn't get that from the changelog entry, sorry. > > > This patch should be backported to kernels as old as 2.6.37, that > > > contain the commit 561925318725a41189a69f36ebe99199b3fb84c4 "USB: xHCI: > > > port remote wakeup implementation". It may be difficult to backport > > > this due to xhci->bus_state being unavailable in older kernels, and the > > > code to split xHCI roothubs into a USB 2.0 roothub and a USB 3.0 roothub > > > not going in until 2.6.39. > > > > If only ChromeOS is affected, why backport it for any stable tree? > > I don't understand this logic. > > The xHCI driver is violating the xHCI spec by not waiting for the port > status change to indicate the port is actually in U0 (active state) > before telling the USB core it's safe to communicate with the port. > Which OS happens to trigger this bug is not important in my mind, since > it's still a bug in the driver. > > ChromeOS can trigger this bug, whether it's running on the 3.8.11 > kernel, or the 3.10.7 kernel. Therefore I would think we would want > this fix in stable kernels, case some other distribution happened to hit > the combination of sysfs writes that causes ChromeOS to trigger this > bug. > > Or are you arguing that we shouldn't backport this because it's just > triggered on one distribution? Am I required to verify all bugs are > triggered on two distributions before they should be considered for > stable? No, my point was if no one can see the bug, then it's not a bug that needs to be fixed in a stable kernel (see Documentation/stable_kernel_rules.txt for details.) As no one else has run into this before now, and no older kernels have shown the problem to anyone, it's not all that "important" to backport this type of thing, right? I'm not saying it's not good to push it to older kernels, just the need is quite low, right? thanks, 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
