[PATCH 1/3] s390/vfio_ccw: Add __must_hold() attribute to vfio_ccw_sch_quiesce()

Add __must_hold() attribute to vfio_ccw_sch_quiesce() in order to let
clang's context analysis know that sch->lock must be held on function
entry. This can also be easily verified when inspecting the function.

Without this annotation this leads to a valid warning when context
analysis is enabled:

drivers/s390/cio/vfio_ccw_drv.c:55:9: warning:
  expecting spinlock 'sch->lock' to be held at start of each loop [-Wthread-safety-analysis]
   55 |                 ret = cio_cancel_halt_clear(sch, &iretry);
      |                       ^

Signed-off-by: Heiko Carstens <[email protected]>
---
 drivers/s390/cio/vfio_ccw_drv.c     | 1 +
 drivers/s390/cio/vfio_ccw_private.h | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index 1a095085bc72..ed9ca77c5b23 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -35,6 +35,7 @@ debug_info_t *vfio_ccw_debug_trace_id;
  * Helpers
  */
 int vfio_ccw_sch_quiesce(struct subchannel *sch)
+	__must_hold(&sch->lock);
 {
 	struct vfio_ccw_parent *parent = dev_get_drvdata(&sch->dev);
 	struct vfio_ccw_private *private = dev_get_drvdata(&parent->dev);
diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index 0501d4bbcdbd..8db29519dbfd 100644
--- a/drivers/s390/cio/vfio_ccw_private.h
+++ b/drivers/s390/cio/vfio_ccw_private.h
@@ -127,7 +127,8 @@ struct vfio_ccw_private {
 	struct work_struct	crw_work;
 } __aligned(8);
 
-int vfio_ccw_sch_quiesce(struct subchannel *sch);
+int vfio_ccw_sch_quiesce(struct subchannel *sch)
+	__must_hold(&sch->lock);
 void vfio_ccw_sch_io_todo(struct work_struct *work);
 void vfio_ccw_crw_todo(struct work_struct *work);
 
-- 
2.53.0