[PATCH v2 06/10] vfio: ccw: Make FSM functions atomic

[Pierre Morel]

We use mutex around the FSM function call to make the FSM
event handling and state change atomic.

Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxxxxxxx>
---
 drivers/s390/cio/vfio_ccw_drv.c     | 3 +--
 drivers/s390/cio/vfio_ccw_private.h | 3 +++
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index 6b7112e..98951d5 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -73,8 +73,6 @@ static void vfio_ccw_sch_io_todo(struct work_struct *work)
 
 	private = container_of(work, struct vfio_ccw_private, io_work);
 	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_INTERRUPT);
-	if (private->mdev)
-		private->state = VFIO_CCW_STATE_IDLE;
 }
 
 static void vfio_ccw_sch_event_todo(struct work_struct *work)
@@ -118,6 +116,7 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
 		return -ENOMEM;
 	private->sch = sch;
 	dev_set_drvdata(&sch->dev, private);
+	mutex_init(&private->state_mutex);
 
 	spin_lock_irq(sch->lock);
 	private->state = VFIO_CCW_STATE_NOT_OPER;
diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index 6c74f73..241176c 100644
--- a/drivers/s390/cio/vfio_ccw_private.h
+++ b/drivers/s390/cio/vfio_ccw_private.h
@@ -51,6 +51,7 @@ struct vfio_ccw_private {
 	struct eventfd_ctx	*io_trigger;
 	struct work_struct	io_work;
 	struct work_struct	event_work;
+	struct mutex		state_mutex;
 } __aligned(8);
 
 extern int vfio_ccw_mdev_reg(struct subchannel *sch);
@@ -92,7 +93,9 @@ extern fsm_func_t *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS];
 static inline void vfio_ccw_fsm_event(struct vfio_ccw_private *private,
 				     int event)
 {
+	mutex_lock(&private->state_mutex);
 	private->state = vfio_ccw_jumptable[private->state][event](private);
+	mutex_unlock(&private->state_mutex);
 }
 
 extern struct workqueue_struct *vfio_ccw_work_q;
-- 
2.7.4