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

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Message-Id: <20250510172419.274616-1-thomas.andreatta2000@gmail.com>
Date: Sat, 10 May 2025 19:24:20 +0200
From: Thomas Andreatta <thomasandreatta2000@...il.com>
To: dpenkler@...il.com
Cc: gregkh@...uxfoundation.org,
	linux-kernel@...r.kernel.org,
	linux-staging@...ts.linux.dev,
	Thomas Andreatta <thomas.andreatta2000@...il.com>
Subject: [PATCH] Staging: gpib: iblib: iboffline check if board is in use

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

Signed-off-by: Thomas Andreatta <thomas.andreatta2000@...il.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