On Sat, Feb 2, 2019 at 9:00 AM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > On Fri, 1 Feb 2019, John Stultz wrote: > > > Hey all, > > Since the 5.0 merge window opened, I've been tripping on frequent > > dwc3 crashes on reboot and suspend, which I've added an example to the > > bottom of this mail. > > > > I've dug in a little bit and sort of have a sense of whats going on. > > > > In ffs_epfile_io(): > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/usb/gadget/function/f_fs.c#n1065 > > > > The completion done is setup on the stack: > > DECLARE_COMPLETION_ONSTACK(done); > > > > Then later we setup a request and queue it: > > req->context = &done; > > ... > > ret = usb_ep_queue(ep->ep, req, GFP_ATOMIC); > > > > Then wait for it: > > if (unlikely(wait_for_completion_interruptible(&done))) { > > /* > > * To avoid race condition with ffs_epfile_io_complete, > > * dequeue the request first then check > > * status. usb_ep_dequeue API should guarantee no race > > * condition with req->complete callback. > > */ > > usb_ep_dequeue(ep->ep, req); > > This code contains a bug: It assumes that usb_ep_dequeue() waits until > the request has been completed. You should insert > > wait_for_completion(&done); > > right here. > > > interrupted = ep->status < 0; > > } > Thanks! This does seem to resolve the issue I'm seeing. Are you planning to send in such a patch, or would it help if I sent it out? thanks -john
