From 69acbaac303e8cb948801a9ddd0ac24e86cc4a1b Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Mon, 8 Jul 2013 13:36:19 +0100 Subject: staging: comedi: COMEDI_CANCEL ioctl should wake up read/write Comedi devices can do blocking read() or write() (or poll()) if an asynchronous command has been set up, blocking for data (for read()) or buffer space (for write()). Various events associated with the asynchronous command will wake up the blocked reader or writer (or poller). It is also possible to force the asynchronous command to terminate by issuing a `COMEDI_CANCEL` ioctl. That shuts down the asynchronous command, but does not currently wake up the blocked reader or writer (or poller). If the blocked task could be woken up, it would see that the command is no longer active and return. The caller of the `COMEDI_CANCEL` ioctl could attempt to wake up the blocked task by sending a signal, but that's a nasty workaround. Change `do_cancel_ioctl()` to wake up the wait queue after it returns from `do_cancel()`. `do_cancel()` can propagate an error return value from the low-level comedi driver's cancel routine, but it always shuts the command down regardless, so `do_cancel_ioctl()` can wake up he wait queue regardless of the return value from `do_cancel()`. Signed-off-by: Ian Abbott Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/comedi_fops.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'drivers/staging') diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c index 8647518259f6..6cdef9d5f8d0 100644 --- a/drivers/staging/comedi/comedi_fops.c +++ b/drivers/staging/comedi/comedi_fops.c @@ -1705,6 +1705,7 @@ static int do_cancel_ioctl(struct comedi_device *dev, unsigned int arg, void *file) { struct comedi_subdevice *s; + int ret; if (arg >= dev->n_subdevices) return -EINVAL; @@ -1721,7 +1722,11 @@ static int do_cancel_ioctl(struct comedi_device *dev, unsigned int arg, if (s->busy != file) return -EBUSY; - return do_cancel(dev, s); + ret = do_cancel(dev, s); + if (comedi_get_subdevice_runflags(s) & SRF_USER) + wake_up_interruptible(&s->async->wait_head); + + return ret; } /* -- cgit v1.2.3-59-g8ed1b