From 13a936bb99fb6385dc8620d24d7111e514448371 Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Wed, 16 Jul 2025 22:08:19 +0000 Subject: neighbour: Protect tbl->phash_buckets[] with a dedicated mutex. tbl->phash_buckets[] is only modified in the slow path by pneigh_create() and pneigh_delete() under the table lock. Both of them are called under RTNL, so no extra lock is needed, but we will remove RTNL from the paths. pneigh_create() looks up a pneigh_entry, and this part can be lockless, but it would complicate the logic like 1. lookup 2. allocate pengih_entry for GFP_KERNEL 3. lookup again but under lock 4. if found, return it after freeing the allocated memory 5. else, return the new one Instead, let's add a per-table mutex and run lookup and allocation under it. Note that updating pneigh_entry part in neigh_add() is still protected by RTNL and will be moved to pneigh_create() in the next patch. Signed-off-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250716221221.442239-15-kuniyu@google.com Signed-off-by: Jakub Kicinski --- include/net/neighbour.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/net/neighbour.h b/include/net/neighbour.h index f8c7261cd4eb..f333f9ebc425 100644 --- a/include/net/neighbour.h +++ b/include/net/neighbour.h @@ -240,6 +240,7 @@ struct neigh_table { unsigned long last_rand; struct neigh_statistics __percpu *stats; struct neigh_hash_table __rcu *nht; + struct mutex phash_lock; struct pneigh_entry __rcu **phash_buckets; }; -- cgit v1.2.3