Hi Thomas,
Sorry for the late answer.
On Thu, 15 Oct 2009 20:28:31 -0000, Thomas Gleixner wrote:
> The conversion of fschmd watchdog ioctl to unlocked_ioctl needs to
> protect the static watchdog_info variable for the WDIOC_GETSUPPORT
> command.
>
> All other commands are safe w/o BKL as the called watchdog functions
> are already serialized with watchdog_lock of the sensor.
>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: lm-sensors@xxxxxxxxxxxxxx
> ---
> drivers/hwmon/fschmd.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> Index: linux-2.6-tip/drivers/hwmon/fschmd.c
> ===================================================================
> --- linux-2.6-tip.orig/drivers/hwmon/fschmd.c
> +++ linux-2.6-tip/drivers/hwmon/fschmd.c
> @@ -844,8 +844,8 @@ static ssize_t watchdog_write(struct fil
> return count;
> }
>
> -static int watchdog_ioctl(struct inode *inode, struct file *filp,
> - unsigned int cmd, unsigned long arg)
> +static long watchdog_ioctl(struct file *filp, unsigned int cmd,
> + unsigned long arg)
> {
> static struct watchdog_info ident = {
> .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
> @@ -857,11 +857,13 @@ static int watchdog_ioctl(struct inode *
>
> switch (cmd) {
> case WDIOC_GETSUPPORT:
> + mutex_lock(&watchdog_data_mutex);
> ident.firmware_version = data->revision;
> if (!nowayout)
> ident.options |= WDIOF_MAGICCLOSE;
> if (copy_to_user((void __user *)arg, &ident, sizeof(ident)))
> ret = -EFAULT;
> + mutex_unlock(&watchdog_data_mutex);
> break;
I'm not sure why we need to hold the mutex here? My understanding is
that watchdog_data_mutex protects watchdog_data_list and each
watchdog's kref. And the above code doesn't touch either.
What I am more worried about is why ident is declared static. This
looks like a bug to me. Instead of abusing watchdog_data_mutex to
workaround this, I'd rather remove the "static". I guess that the
current code happens to work because neither data->revision nor
nowayout can change over time, but this looks needlessly fragile.
Hans, any comment?
>
> case WDIOC_GETSTATUS:
> @@ -921,7 +923,7 @@ static const struct file_operations watc
> .open = watchdog_open,
> .release = watchdog_release,
> .write = watchdog_write,
> - .ioctl = watchdog_ioctl,
> + .unlocked_ioctl = watchdog_ioctl,
> };
--
Jean Delvare
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