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

On Sat, May 10, 2025 at 07:24:20PM +0200, Thomas Andreatta wrote:
> 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) {

We're not holding this mutex in ibopen() and not necessarily
in ibclose() either so this doesn't work.  It's racy.

You'd have to change the ioctl as well.

regards,
dan carpenter

On Sat, May 10, 2025 at 07:24:20PM +0200, Thomas Andreatta wrote:
> 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) {

use_count is never zero for an initialised board so this would always
return -EBUSY not allowing a board to be placed offline

> +		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
>