neighbour: Protect tbl->phash_buckets[] with a dedicated mutex.

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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 <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-15-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

...

This commit is contained in:

Kuniyuki Iwashima 2025-07-16 22:08:19 +00:00 • committed by Jakub Kicinski

parent b8b7ed1ea8

commit 13a936bb99

2 changed files with 22 additions and 18 deletions

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1

include/net/neighbour.h

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39

net/core/neighbour.c

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