I think usbnet_stop() raced with the dev->bh tasklet, which by itself might not be a problem (usbnet_stop() later kills the tasklet itself, so it should expect that it can be running before that). The issue is that it calls usbnet_terminate_urbs() before that, which temporarily installs a waitqueue in dev->wait in order to be able to wait on the tasklet to run and finish up some queues. The waiting itself looks okay, but the access to 'dev->wait' is totally unprotected and can race arbitrarily. I think in this case usbnet_bh() managed to succeed it's dev->wait check just before usbnet_terminate_urbs() sets it back to NULL. The latter then finishes and the waitqueue_t structure on its stack gets overwritten by other functions halfway through the wake_up() call in usbnet_bh(). I think the best solution would be to just make dev->wait a directly embedded structure inside struct usbnet instead of a pointer to something stack-allocated. usbnet_bh() could just call wake_up() unconditionally (if empty it will be a noop), and then one other check for !dev->wait could be replaced with a call to waitqueue_active(). Then the waitqueue-internal locks should be enough to protect all accesses. -- 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
