On Wed, Sep 24, 2014 at 04:36:22PM +0300, Octavian Purdila wrote: > On Wed, Sep 24, 2014 at 1:48 PM, Johan Hovold <johan@xxxxxxxxxx> wrote: > > On Fri, Sep 19, 2014 at 11:22:42PM +0300, Octavian Purdila wrote: > > <snip> > > >> + * dln2_dev.mod_rx_slots and then the echo header field to index the > >> + * slots field and find the receive context for a particular > >> + * request. > >> + */ > >> +struct dln2_mod_rx_slots { > >> + /* RX slots bitmap */ > >> + unsigned long bmap; > >> + > >> + /* used to wait for a free RX slot */ > >> + wait_queue_head_t wq; > >> + > >> + /* used to wait for an RX operation to complete */ > >> + struct dln2_rx_context slots[DLN2_MAX_RX_SLOTS]; > >> + > >> + /* device has been disconnected */ > >> + bool disconnected; > > > > This belongs in the dln2_dev struct. > > > > I think you're overcomplicating the disconnect handling by intertwining > > it with your slots. > > > > Add a lock, an active-transfer counter, a disconnected flag, and a wait > > queue to struct dln2_dev. > > > > I agree that disconnected is better suited in dln2_dev. > > However, I don't think that we need the active-transfer counter and a > new wait queue. We can simply use the existing waiting queues and the > implicit alloc_rx_slot()/free_rx_slot() calls to see if we are still > waiting for I/O. Just because you can reuse them doesn't mean it's a good idea. By separating a generic disconnect solution from your custom slot implementation we get something that is way easier to verify for correctness and that could also be reused in other drivers. > <snip> > > >> + > >> +static int _dln2_transfer(struct dln2_dev *dln2, u16 handle, u16 cmd, > >> + const void *obuf, unsigned obuf_len, > >> + void *ibuf, unsigned *ibuf_len) > >> +{ > >> + int ret = 0; > >> + u16 result; > >> + int rx_slot; > >> + unsigned long flags; > >> + struct dln2_response *rsp; > >> + struct dln2_rx_context *rxc; > >> + struct device *dev; > >> + const int timeout = DLN2_USB_TIMEOUT * HZ / 1000; > >> + struct dln2_mod_rx_slots *rxs = &dln2->mod_rx_slots[handle]; > >> + > > > > Check the disconnected flag before incrementing the transfer count > > (while holding the device lock) here. Then decrement counter before > > returning and wake up an waiters if disconnected below. > > > > That is sufficient to implement wait-until-io-has-completed. Anything > > else you do below and in the helper functions is only to speed things > > up at disconnect (and can be done without locking the device). > > > >> + rx_slot = alloc_rx_slot(rxs); > >> + if (rx_slot < 0) > >> + return rx_slot; > >> + > >> + dev = &dln2->interface->dev; > >> + > >> + ret = dln2_send_wait(dln2, handle, cmd, rx_slot, obuf, obuf_len); > >> + if (ret < 0) { > >> + free_rx_slot(dln2, rxs, rx_slot); > > > > goto out_free_rx_slot > > > >> + dev_err(dev, "USB write failed: %d", ret); > >> + return ret; > >> + } > >> + > >> + rxc = &rxs->slots[rx_slot]; > >> + > >> + ret = wait_for_completion_interruptible_timeout(&rxc->done, timeout); > >> + if (ret <= 0) { > >> + if (!ret) > >> + ret = -ETIMEDOUT; > >> + goto out_free_rx_slot; > >> + } > >> + > >> + spin_lock_irqsave(&rxs->lock, flags); > >> + > >> + if (!rxc->urb) { > > > > Just check the disconnected flag directly here. Locking not needed (see > > below). > > > > I think we need the check here for the case when we cancel the > completion and no response has been received yet. In that case rx->urb > will be NULL (even if we remove the rx->urb = NULL statement in > dln2_stop). But the disconnect flag will also be set and makes it more obvious what is going on. [...] > >> +static void dln2_disconnect(struct usb_interface *interface) > >> +{ > >> + struct dln2_dev *dln2 = usb_get_intfdata(interface); > >> + > > > > First set the disconnected flag directly here to prevent any new > > transfers from starting. > > > >> + dln2_stop(dln2); > > > > Then do all the completions (to speed things up somewhat). > > > > Then wait for the transfer counter to reach 0. > > > >> + mfd_remove_devices(&interface->dev); > >> + dln2_free(dln2); > >> +} > >> + > > As I mentioned above, I don't think we need the transfer counter, we > can rely on the slots bitmap. Yes, a counter is simpler but it also > requires adding a new waiting queue and a new lock. That's really not a big deal. See above. Johan -- 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