linux-kernel - Re: [PATCH] fsi: sbefifo: Use interruptible mutex locking

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Message-ID: <CACPK8XcVDAKxiPGmcrjsyHJ5LUt4xkCm3sJzb5d6xCXr_+dzrg@mail.gmail.com>
Date:   Fri, 15 Oct 2021 05:31:08 +0000
From:   Joel Stanley <joel@....id.au>
To:     Eddie James <eajames@...ux.ibm.com>
Cc:     Jeremy Kerr <jk@...abs.org>,
        Alistair Popple <alistair@...ple.id.au>,
        linux-fsi@...ts.ozlabs.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fsi: sbefifo: Use interruptible mutex locking

On Tue, 3 Aug 2021 at 21:30, Eddie James <eajames@...ux.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@...ux.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@....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
>