uio: use threaded interrupts

Split the existing uio_interrupt into a hardirq handler and a thread
function. The hardirq handler deals with the interrupt source in
hardware, the thread function notifies userspace that there is an event
to be handled.
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Link: https://lore.kernel.org/r/20240408234050.2056374-3-chris.packham@alliedtelesis.co.nzSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/uio/uio.c

@@ -442,18 +442,27 @@ EXPORT_SYMBOL_GPL(uio_event_notify);
  * @irq: IRQ number, can be UIO_IRQ_CYCLIC for cyclic timer
  * @dev_id: Pointer to the devices uio_device structure
  */
-static irqreturn_t uio_interrupt(int irq, void *dev_id)
+static irqreturn_t uio_interrupt_handler(int irq, void *dev_id)
 {
 	struct uio_device *idev = (struct uio_device *)dev_id;
 	irqreturn_t ret;
 
 	ret = idev->info->handler(irq, idev->info);
 	if (ret == IRQ_HANDLED)
-		uio_event_notify(idev->info);
+		ret = IRQ_WAKE_THREAD;
 
 	return ret;
 }
 
+static irqreturn_t uio_interrupt_thread(int irq, void *dev_id)
+{
+	struct uio_device *idev = (struct uio_device *)dev_id;
+
+	uio_event_notify(idev->info);
+
+	return IRQ_HANDLED;
+}
+
 struct uio_listener {
 	struct uio_device *dev;
 	s32 event_count;
@@ -1024,8 +1033,8 @@ int __uio_register_device(struct module *owner,
 		 * FDs at the time of unregister and therefore may not be
 		 * freed until they are released.
 		 */
-		ret = request_irq(info->irq, uio_interrupt,
-				  info->irq_flags, info->name, idev);
+		ret = request_threaded_irq(info->irq, uio_interrupt_handler, uio_interrupt_thread,
+					   info->irq_flags, info->name, idev);
 		if (ret) {
 			info->uio_dev = NULL;
 			goto err_request_irq;