Hans de Goede has reported a difficulty in the Linux port of libusb. When a device is removed, the poll() system call in usbfs starts returning POLLERR as soon as udev->state is set to USB_STATE_NOTATTACHED, but the outstanding URBs are not available for reaping until some time later (after usbdev_remove() has been called). This is awkward for libusb or other usbfs clients, although not an insuperable problem. At any rate, it's easy to change usbfs so that it returns POLLHUP as soon as the state becomes USB_STATE_NOTATTACHED but it doesn't return POLLERR until after the outstanding URBs have completed. That's what this patch does; it uses the fact that ps->list is always on the dev->filelist list until usbdev_remove() takes it off, which happens after all the outstanding URBs have been cancelled. Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> Reported-by: Hans de Goede <hdegoede@xxxxxxxxxx> --- [as1802] drivers/usb/core/devio.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) Index: usb-4.x/drivers/usb/core/devio.c =================================================================== --- usb-4.x.orig/drivers/usb/core/devio.c +++ usb-4.x/drivers/usb/core/devio.c @@ -2581,7 +2581,9 @@ static unsigned int usbdev_poll(struct f if (file->f_mode & FMODE_WRITE && !list_empty(&ps->async_completed)) mask |= POLLOUT | POLLWRNORM; if (!connected(ps)) - mask |= POLLERR | POLLHUP; + mask |= POLLHUP; + if (list_empty(&ps->list)) + mask |= POLLERR; return mask; } -- 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
