On 10/19, Hou Tao wrote:
From: Hou Tao <houtao1@xxxxxxxxxx>
Except for waiting_for_gp list, there are no concurrent operations on free_by_rcu, free_llist and free_llist_extra lists, so use __llist_del_all() instead of llist_del_all(). waiting_for_gp list can be deleted by RCU callback concurrently, so still use llist_del_all().
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx> --- kernel/bpf/memalloc.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c index 48e606aaacf0..7f45744a09f7 100644 --- a/kernel/bpf/memalloc.c +++ b/kernel/bpf/memalloc.c @@ -422,14 +422,17 @@ static void drain_mem_cache(struct bpf_mem_cache *c) /* No progs are using this bpf_mem_cache, but htab_map_free() called * bpf_mem_cache_free() for all remaining elements and they can be in * free_by_rcu or in waiting_for_gp lists, so drain those lists now. + * + * Except for waiting_for_gp list, there are no concurrent operations + * on these lists, so it is safe to use __llist_del_all(). */ llist_for_each_safe(llnode, t, __llist_del_all(&c->free_by_rcu)) free_one(c, llnode); llist_for_each_safe(llnode, t, llist_del_all(&c->waiting_for_gp)) free_one(c, llnode); - llist_for_each_safe(llnode, t, llist_del_all(&c->free_llist)) + llist_for_each_safe(llnode, t, __llist_del_all(&c->free_llist)) free_one(c, llnode); - llist_for_each_safe(llnode, t, llist_del_all(&c->free_llist_extra)) + llist_for_each_safe(llnode, t, __llist_del_all(&c->free_llist_extra)) free_one(c, llnode);
Acked-by: Stanislav Fomichev <sdf@xxxxxxxxxx> Seems safe even without the previous patch? OTOH, do we really care about __lllist vs llist in the cleanup path? Might be safer to always do llist_del_all everywhere?
}
-- 2.29.2
