On Wed, Apr 25, 2018 at 01:45:06AM +0200, Niklas Söderlund wrote:
> Store the group pointer before disassociating the VIN from the group.
>
> Fixes: 3bb4c3bc85bf77a7 ("media: rcar-vin: add group allocator functions")
> Reported-by: Colin Ian King <colin.k...@canonical.com>
> Signed-off-by: Niklas Söderlund <niklas.soderlund+rene...@ragnatech.se>
> ---
> drivers/media/platform/rcar-vin/rcar-core.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/media/platform/rcar-vin/rcar-core.c
> b/drivers/media/platform/rcar-vin/rcar-core.c
> index 7bc2774a11232362..d3072e166a1ca24f 100644
> --- a/drivers/media/platform/rcar-vin/rcar-core.c
> +++ b/drivers/media/platform/rcar-vin/rcar-core.c
> @@ -338,19 +338,21 @@ static int rvin_group_get(struct rvin_dev *vin)
>
> static void rvin_group_put(struct rvin_dev *vin)
> {
> - mutex_lock(&vin->group->lock);
> + struct rvin_group *group = vin->group;
> +
> + mutex_lock(&group->lock);
Hi Niklas, its not clear to me why moving the lock is safe.
Could you explain the locking scheme a little?
>
> vin->group = NULL;
> vin->v4l2_dev.mdev = NULL;
>
> - if (WARN_ON(vin->group->vin[vin->id] != vin))
> + if (WARN_ON(group->vin[vin->id] != vin))
> goto out;
>
> - vin->group->vin[vin->id] = NULL;
> + group->vin[vin->id] = NULL;
> out:
> - mutex_unlock(&vin->group->lock);
> + mutex_unlock(&group->lock);
>
> - kref_put(&vin->group->refcount, rvin_group_release);
> + kref_put(&group->refcount, rvin_group_release);
> }
>
> /*
> -----------------------------------------------------------------------------
> --
> 2.17.0
>
