On 12 Jan 2023 22:59:54 -0800 Boqun Feng <boqun.feng@xxxxxxxxx>
> --- a/kernel/rcu/srcutree.c
> +++ b/kernel/rcu/srcutree.c
> @@ -1267,6 +1267,8 @@ static void __synchronize_srcu(struct srcu_struct *ssp, bool do_norm)
> {
> struct rcu_synchronize rcu;
>
> + srcu_lock_sync(&ssp->dep_map);
> +
> RCU_LOCKDEP_WARN(lockdep_is_held(ssp) ||
> lock_is_held(&rcu_bh_lock_map) ||
> lock_is_held(&rcu_lock_map) ||
> --
> 2.38.1
The following deadlock is able to escape srcu_lock_sync() because the
__lock_release folded in sync leaves one lock on the sync side.
cpu9 cpu0
--- ---
lock A srcu_lock_acquire(&ssp->dep_map);
srcu_lock_sync(&ssp->dep_map);
lock A
