Hi, On 12/12/2013 01:07 AM, Sarah Sharp wrote:
Hi Hans, I've been testing the UAS code you sent a pull request for against 3.13-rc1, and I've run into a rather nasty issue with USB disconnect. I ran some tests with a USB 3.0 storage device under xHCI. The disk has three 10GB partitions: ext3 (sdb1), ext4 (sdb2), and fat32 (sdb4). There was a btrfs partition on sdb3, but I deleted it. If I start to play a movie on the ext4 partition, and then yank the USB cable, the uas driver is unbound from the device. It looks like something goes wrong in the SCSI layer shortly after that, causing an oops in sysfs_remove_group(). If I plug in the device again, the uas driver loads and sdb is recognized, but the partitions aren't mounted. If I disconnect the device, the USB core hub thread (khubd) tries to unbind the interface, and the uas driver's disconnect function hangs. At that point, USB device hotplug on any ports (including EHCI ports) are not recognized, because khub is hung. Submitting and completing URBs still work, since that doesn't involve khubd. The end result is that disconnecting the UAS device causes USB hotplug to be lost on unrelated ports, while other USB devices that were attached at the time of the disconnect still work. I can reproduce this behavior when the UAS device is attached to the EHCI port only, so it's not an xHCI specific bug. If I use the "no UAS" quirk to make the usb-storage driver bind to the device, I can trigger the oops from the SCSI layer, but the partitions are always mounted and khubd doesn't hang.
Hmm, interesting I myself have experienced a similar bug during testing, see: http://www.spinics.net/lists/linux-scsi/msg70002.html On which I've not received any useful reply myself yet. It seems that the scsi subsys and/or sd driver has some issues with not tearing things down in the proper order when a disk is in use while the scsi-host it is attached to gets removed. As you can see in the reproduction instructions in my mail, the BUG does not happen until I cd out of the mountpoint, at which point the kernel tries to clean things up, and the clean up at that point happens in a different order then it happens when unplugging the disk while the mountpoint is not busy. Regards, Hans -- 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
