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 If the blocked task could be woken up, it would see that the command is no longer active and return.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 <abbotti@mev.co.uk> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -1705,6 +1705,7 @@ static int do_cancel_ioctl(struct comedi_device *dev, unsigned int arg,
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void *file)
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{
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struct comedi_subdevice *s;
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int ret;
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if (arg >= dev->n_subdevices)
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return -EINVAL;
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@ -1721,7 +1722,11 @@ static int do_cancel_ioctl(struct comedi_device *dev, unsigned int arg,
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if (s->busy != file)
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return -EBUSY;
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return do_cancel(dev, s);
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ret = do_cancel(dev, s);
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if (comedi_get_subdevice_runflags(s) & SRF_USER)
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wake_up_interruptible(&s->async->wait_head);
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return ret;
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}
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/*
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