[PATCH] Staging: gpib: iblib: iboffline check if board is in use

[Thomas Andreatta <thomasandreatta2000@gmail.com>]

Ensures that a board cannot be taken offline while it's still in use.

Signed-off-by: Thomas Andreatta <thomas.andreatta2000@gmail.com>
---
 drivers/staging/gpib/common/iblib.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/gpib/common/iblib.c b/drivers/staging/gpib/common/iblib.c
index 7a44517464ab..0ab5680457ac 100644
--- a/drivers/staging/gpib/common/iblib.c
+++ b/drivers/staging/gpib/common/iblib.c
@@ -240,7 +240,6 @@ int ibonline(struct gpib_board *board)
 	return 0;
 }
 
-/* XXX need to make sure board is generally not in use (grab board lock?) */
 int iboffline(struct gpib_board *board)
 {
 	int retval;
@@ -250,6 +249,15 @@ int iboffline(struct gpib_board *board)
 	if (!board->interface)
 		return -ENODEV;
 
+	/* Ensure board is not in use */
+	if (mutex_lock_interruptible(&board->user_mutex))
+		return -ERESTARTSYS;
+
+	if (board->use_count > 0) {
+		mutex_unlock(&board->user_mutex);
+		return -EBUSY;
+	}
+
 	if (board->autospoll_task && !IS_ERR(board->autospoll_task)) {
 		retval = kthread_stop(board->autospoll_task);
 		if (retval)
@@ -262,6 +270,7 @@ int iboffline(struct gpib_board *board)
 	board->online = 0;
 	dev_dbg(board->gpib_dev, "board offline\n");
 
+	mutex_unlock(&board->user_mutex);
 	return 0;
 }
 
-- 
2.34.1