[char-misc 1/2 for 4.11] mei: fix deadlock on mei reset

[Tomas Winkler]

This patch fixes 'mei: synchronize irq before initiating a reset'
The patch had introduced a deadlock between irq thread and mei_reset()
as they are both holding the same device lock.

---> device_lock:
	mei_reset()
                        <---- interrupt thread
	                        device_lock
---> synchornize_irq()
       wait on interrupt thread == (dead lock)

The fix is to call synchronize_irq
prior to call locked mei_reset function.

Cc: <stable@xxxxxxxxxxxxxxx> #4.10+
Fixes: f302bb0de6ac (mei: synchronize irq before initiating a reset)
Signed-off-by: Tomas Winkler <tomas.winkler@xxxxxxxxx>
---
 drivers/misc/mei/init.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/mei/init.c b/drivers/misc/mei/init.c
index cfb1cdf176fa..13c55b8f9261 100644
--- a/drivers/misc/mei/init.c
+++ b/drivers/misc/mei/init.c
@@ -124,8 +124,6 @@ int mei_reset(struct mei_device *dev)
 
 	mei_clear_interrupts(dev);
 
-	mei_synchronize_irq(dev);
-
 	/* we're already in reset, cancel the init timer
 	 * if the reset was called due the hbm protocol error
 	 * we need to call it before hw start
@@ -304,6 +302,9 @@ static void mei_reset_work(struct work_struct *work)
 		container_of(work, struct mei_device,  reset_work);
 	int ret;
 
+	mei_clear_interrupts(dev);
+	mei_synchronize_irq(dev);
+
 	mutex_lock(&dev->device_lock);
 
 	ret = mei_reset(dev);
@@ -328,6 +329,9 @@ void mei_stop(struct mei_device *dev)
 
 	mei_cancel_work(dev);
 
+	mei_clear_interrupts(dev);
+	mei_synchronize_irq(dev);
+
 	mutex_lock(&dev->device_lock);
 
 	dev->dev_state = MEI_DEV_POWER_DOWN;
-- 
2.7.4