diff options
| -rw-r--r-- | net/sched/cls_api.c | 24 |
1 files changed, 18 insertions, 6 deletions
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c index d29e79d98a69..0b2219adf520 100644 --- a/net/sched/cls_api.c +++ b/net/sched/cls_api.c @@ -275,15 +275,27 @@ void tcf_block_put(struct tcf_block *block) /* XXX: Standalone actions are not allowed to jump to any chain, and * bound actions should be all removed after flushing. However, - * filters are destroyed in RCU callbacks, we have to flush and wait - * for them inside the loop, otherwise we race with RCU callbacks on - * this list. + * filters are destroyed in RCU callbacks, we have to hold the chains + * first, otherwise we would always race with RCU callbacks on this list + * without proper locking. */ - list_for_each_entry_safe(chain, tmp, &block->chain_list, list) { + + /* Wait for existing RCU callbacks to cool down. */ + rcu_barrier(); + + /* Hold a refcnt for all chains, except 0, in case they are gone. */ + list_for_each_entry(chain, &block->chain_list, list) + if (chain->index) + tcf_chain_hold(chain); + + /* No race on the list, because no chain could be destroyed. */ + list_for_each_entry(chain, &block->chain_list, list) tcf_chain_flush(chain); - rcu_barrier(); - } + /* Wait for RCU callbacks to release the reference count. */ + rcu_barrier(); + + /* At this point, all the chains should have refcnt == 1. */ list_for_each_entry_safe(chain, tmp, &block->chain_list, list) tcf_chain_put(chain); kfree(block); |