On Fri, Jun 12, 2015 at 09:24:40PM -0700, sfel...@gmail.com wrote:
> From: Scott Feldman <sfel...@gmail.com>
>
> rocker->neigh_tbl_next_index is used to generate unique indices for neigh
> entries programmed into the device. The way new indices were generated was
> racy with the new prepare-commit transaction model. A simple fix here
> removes the race. The race was with two processes getting the same index,
> one process using prepare-commit, the other not:
>
> Proc A Proc B
>
> PREPARE phase
> get neigh_tbl_next_index
>
> NONE phase
> get neigh_tbl_next_index
> neigh_tbl_next_index++
>
> COMMIT phase
> neigh_tbl_next_index++
>
> Both A and B got the same index. The fix is to store and increment
> neigh_tbl_next_index in the PREPARE (or NONE) phase and use value in COMMIT
> phase:
>
> Proc A Proc B
>
> PREPARE phase
> get neigh_tbl_next_index
> neigh_tbl_next_index++
>
> NONE phase
> get neigh_tbl_next_index
> neigh_tbl_next_index++
>
> COMMIT phase
> // use value stashed in PREPARE phase
>
> Reported-by: Simon Horman <simon.hor...@netronome.com>
> Signed-off-by: Scott Feldman <sfel...@gmail.com>
Reviewed-by: Simon Horman <simon.hor...@netronome.com>
> ---
> drivers/net/ethernet/rocker/rocker.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/rocker/rocker.c
> b/drivers/net/ethernet/rocker/rocker.c
> index c6a6e3c..a9d1559 100644
> --- a/drivers/net/ethernet/rocker/rocker.c
> +++ b/drivers/net/ethernet/rocker/rocker.c
> @@ -2901,10 +2901,10 @@ static void _rocker_neigh_add(struct rocker *rocker,
> enum switchdev_trans trans,
> struct rocker_neigh_tbl_entry *entry)
> {
> - entry->index = rocker->neigh_tbl_next_index;
> + if (trans != SWITCHDEV_TRANS_COMMIT)
> + entry->index = rocker->neigh_tbl_next_index++;
> if (trans == SWITCHDEV_TRANS_PREPARE)
> return;
> - rocker->neigh_tbl_next_index++;
> entry->ref_count++;
> hash_add(rocker->neigh_tbl, &entry->entry,
> be32_to_cpu(entry->ip_addr));
> --
> 1.7.10.4
>
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