Lock checker noted an inverted lock order between neigh_change_state
(neighbor lock then table lock) and neigh_periodic_work (table lock and
then neighbor lock) resulting in:
[ 121.057652] ======================================================
[ 121.058740] WARNING: possible circular locking dependency detected
[ 121.059861] 4.20.0-rc6+ #43 Not tainted
[ 121.060546] ------------------------------------------------------
[ 121.061630] kworker/0:2/65 is trying to acquire lock:
[ 121.062519] (____ptrval____) (&n->lock){++--}, at: neigh_periodic_work+0x237/0x324
[ 121.063894]
[ 121.063894] but task is already holding lock:
[ 121.064920] (____ptrval____) (&tbl->lock){+.-.}, at: neigh_periodic_work+0x194/0x324
[ 121.066274]
[ 121.066274] which lock already depends on the new lock.
[ 121.066274]
[ 121.067693]
[ 121.067693] the existing dependency chain (in reverse order) is:
...
Fix by renaming neigh_change_state to neigh_update_gc_list, changing
it to only manage whether an entry should be on the gc_list and taking
locks in the same order as neigh_periodic_work. Invoke at the end of
neigh_update only if diff between old or new states has the PERMANENT
flag set.
Fixes: 8cc196d6ef ("neighbor: gc_list changes should be protected by table lock")
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
9c29a2f55e