[S390] tape: fix race with stack local wait_queue_head_t.

A wait_event call with a stack local wait_queue_head_t structure that is
used to do the wake up for the wait_event is inherently racy. After the
wait_event finished the wake_up call might not have completed yet.
Replace the stack local wait_queue_head_t in tape_do_io and
tape_do_io_interruptible with a per device wait queue.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/s390/char/tape.h b/drivers/s390/char/tape.h
index dddf8d62c153..d0d565a05dfe 100644
--- a/drivers/s390/char/tape.h
+++ b/drivers/s390/char/tape.h
@@ -231,6 +231,9 @@ struct tape_device {
         /* Request queue. */
         struct list_head                req_queue;
 
+        /* Request wait queue. */
+        wait_queue_head_t               wait_queue;
+
         /* Each tape device has (currently) two minor numbers. */
         int                             first_minor;