On Fri, May 29, 2020 at 05:48:26PM -0700, Guenter Roeck wrote: > On Fri, May 29, 2020 at 4:50 PM Nicolas Boichat <drinkcat@xxxxxxxxxxxx> wrote: > > > > On Sat, May 30, 2020 at 3:59 AM Dmitry Torokhov > > <dmitry.torokhov@xxxxxxxxx> wrote: > > > > > > usbhid tries to give the device 50 milliseconds to drain its queues > > > when opening the device, but does it naively by simply sleeping in open > > > handler, which slows down device probing (and thus may affect overall > > > boot time). > > > > > > However we do not need to sleep as we can instead mark a point of time > > > in the future when we should start processing the events. > > > > > > Reported-by: Nicolas Boichat <drinkcat@xxxxxxxxxxxx> > > > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx> > > > --- > > > drivers/hid/usbhid/hid-core.c | 27 +++++++++++++++------------ > > > drivers/hid/usbhid/usbhid.h | 1 + > > > 2 files changed, 16 insertions(+), 12 deletions(-) > > > > > > diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c > > > index c7bc9db5b192..e69992e945b2 100644 > > > --- a/drivers/hid/usbhid/hid-core.c > > > +++ b/drivers/hid/usbhid/hid-core.c > > > @@ -95,6 +95,19 @@ static int hid_start_in(struct hid_device *hid) > > > set_bit(HID_NO_BANDWIDTH, &usbhid->iofl); > > > } else { > > > clear_bit(HID_NO_BANDWIDTH, &usbhid->iofl); > > > + > > > + if (test_and_clear_bit(HID_RESUME_RUNNING, > > > + &usbhid->iofl)) { > > > + /* > > > + * In case events are generated while nobody was > > > + * listening, some are released when the device > > > + * is re-opened. Wait 50 msec for the queue to > > > + * empty before allowing events to go through > > > + * hid. > > > + */ > > > + usbhid->input_start_time = jiffies + > > > + msecs_to_jiffies(50); > > > + } > > > } > > > } > > > spin_unlock_irqrestore(&usbhid->lock, flags); > > > @@ -280,7 +293,8 @@ static void hid_irq_in(struct urb *urb) > > > if (!test_bit(HID_OPENED, &usbhid->iofl)) > > > break; > > > usbhid_mark_busy(usbhid); > > > - if (!test_bit(HID_RESUME_RUNNING, &usbhid->iofl)) { > > > + if (!test_bit(HID_RESUME_RUNNING, &usbhid->iofl) && > > > + time_after(jiffies, usbhid->input_start_time)) { > > > > Are we worried about jiffies overflowing (32-bit@1000Hz is "only" 49.7 days...) > > > > time_after() is overflow-safe. That is why it is used and jiffies is > not compared directly. Well, it is overflow safe, but still can not measure more than 50 days, so if you have a device open for 50+ days there will be a 50msec gap where it may lose events. I guess we can switch to ktime(). A bit more expensive on 32 bits, but in reality I do not think anyone would care. Thanks. -- Dmitry