[S390] vmur: Use wait queue instead of mutex to serialize open

If user space opens a unit record device node then vmur is leaving the kernel
with lock open_mutex still held to prevent other processes from opening the
device simultaneously. This causes lockdep to complain about a lock held when
returning to user space.
Now the mutex is replaced by a wait queue to serialize device open.

Signed-off-by: Frank Munzert <munzert@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/s390/char/vmur.h b/drivers/s390/char/vmur.h
index fa959644735a..fa320ad4593d 100644
--- a/drivers/s390/char/vmur.h
+++ b/drivers/s390/char/vmur.h
@@ -62,7 +62,6 @@ struct file_control_block {
 struct urdev {
         struct ccw_device *cdev;        /* Backpointer to ccw device */
         struct mutex io_mutex;          /* Serialises device IO */
-        struct mutex open_mutex;        /* Serialises access to device */
         struct completion *io_done;     /* do_ur_io waits; irq completes */
         struct device *device;
         struct cdev *char_device;
@@ -71,6 +70,9 @@ struct urdev {
         int class;                      /* VM device class */
         int io_request_rc;              /* return code from I/O request */
         atomic_t ref_count;             /* reference counter */
+        wait_queue_head_t wait;         /* wait queue to serialize open */
+        int open_flag;                  /* "urdev is open" flag */
+        spinlock_t open_lock;           /* serialize critical sections */
 };
 
 /*