[PATCH] fsi: sbefifo: Use interruptible mutex locking

[PATCH] fsi: sbefifo: Use interruptible mutex locking

[Eddie James]

Some SBE operations have extremely large responses and can require
several minutes to process the response. During this time, the device
lock must be held. If another process attempts an operation, it will
wait for the mutex for longer than the kernel hung task watchdog
allows. Therefore, use the interruptible function to lock the mutex.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
---
 drivers/fsi/fsi-sbefifo.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/fsi/fsi-sbefifo.c b/drivers/fsi/fsi-sbefifo.c
index 84cb965bfed5..a8d8e47e6fb2 100644
--- a/drivers/fsi/fsi-sbefifo.c
+++ b/drivers/fsi/fsi-sbefifo.c
@@ -740,7 +740,9 @@ int sbefifo_submit(struct device *dev, const __be32 *command, size_t cmd_len,
         iov_iter_kvec(&resp_iter, WRITE, &resp_iov, 1, rbytes);
 
 	/* Perform the command */
-	mutex_lock(&sbefifo->lock);
+	rc = mutex_lock_interruptible(&sbefifo->lock);
+	if (rc)
+		return rc;
 	rc = __sbefifo_submit(sbefifo, command, cmd_len, &resp_iter);
 	mutex_unlock(&sbefifo->lock);
 
@@ -820,7 +822,9 @@ static ssize_t sbefifo_user_read(struct file *file, char __user *buf,
 	iov_iter_init(&resp_iter, WRITE, &resp_iov, 1, len);
 
 	/* Perform the command */
-	mutex_lock(&sbefifo->lock);
+	rc = mutex_lock_interruptible(&sbefifo->lock);
+	if (rc)
+		goto bail;
 	rc = __sbefifo_submit(sbefifo, user->pending_cmd, cmd_len, &resp_iter);
 	mutex_unlock(&sbefifo->lock);
 	if (rc < 0)
@@ -875,7 +879,9 @@ static ssize_t sbefifo_user_write(struct file *file, const char __user *buf,
 		user->pending_len = 0;
 
 		/* Trigger reset request */
-		mutex_lock(&sbefifo->lock);
+		rc = mutex_lock_interruptible(&sbefifo->lock);
+		if (rc)
+			goto bail;
 		rc = sbefifo_request_reset(user->sbefifo);
 		mutex_unlock(&sbefifo->lock);
 		if (rc == 0)
-- 
2.27.0

Re: [PATCH] fsi: sbefifo: Use interruptible mutex locking

[Joel Stanley]

On Tue, 3 Aug 2021 at 21:30, Eddie James <eajames@linux.ibm.com> wrote:
>
> Some SBE operations have extremely large responses and can require
> several minutes to process the response. During this time, the device
> lock must be held. If another process attempts an operation, it will
> wait for the mutex for longer than the kernel hung task watchdog
> allows. Therefore, use the interruptible function to lock the mutex.
>
> Signed-off-by: Eddie James <eajames@linux.ibm.com>

I think this is okay. I'm not familiar with the use of
mutex_lock_interruptible, so if anyone else wants to ask questions
please do.

Reviewed-by: Joel Stanley <joel@jms.id.au>

> ---
>  drivers/fsi/fsi-sbefifo.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/fsi/fsi-sbefifo.c b/drivers/fsi/fsi-sbefifo.c
> index 84cb965bfed5..a8d8e47e6fb2 100644
> --- a/drivers/fsi/fsi-sbefifo.c
> +++ b/drivers/fsi/fsi-sbefifo.c
> @@ -740,7 +740,9 @@ int sbefifo_submit(struct device *dev, const __be32 *command, size_t cmd_len,
>          iov_iter_kvec(&resp_iter, WRITE, &resp_iov, 1, rbytes);
>
>         /* Perform the command */
> -       mutex_lock(&sbefifo->lock);
> +       rc = mutex_lock_interruptible(&sbefifo->lock);
> +       if (rc)
> +               return rc;
>         rc = __sbefifo_submit(sbefifo, command, cmd_len, &resp_iter);
>         mutex_unlock(&sbefifo->lock);
>
> @@ -820,7 +822,9 @@ static ssize_t sbefifo_user_read(struct file *file, char __user *buf,
>         iov_iter_init(&resp_iter, WRITE, &resp_iov, 1, len);
>
>         /* Perform the command */
> -       mutex_lock(&sbefifo->lock);
> +       rc = mutex_lock_interruptible(&sbefifo->lock);
> +       if (rc)
> +               goto bail;
>         rc = __sbefifo_submit(sbefifo, user->pending_cmd, cmd_len, &resp_iter);
>         mutex_unlock(&sbefifo->lock);
>         if (rc < 0)
> @@ -875,7 +879,9 @@ static ssize_t sbefifo_user_write(struct file *file, const char __user *buf,
>                 user->pending_len = 0;
>
>                 /* Trigger reset request */
> -               mutex_lock(&sbefifo->lock);
> +               rc = mutex_lock_interruptible(&sbefifo->lock);
> +               if (rc)
> +                       goto bail;
>                 rc = sbefifo_request_reset(user->sbefifo);
>                 mutex_unlock(&sbefifo->lock);
>                 if (rc == 0)
> --
> 2.27.0
>