rocker: fix neigh tbl index increment race
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.horman@netronome.com>
Signed-off-by: Scott Feldman <sfeldma@gmail.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
1 file changed