Re: [PATCH] sched/fair: Fix call walk_tg_tree_from() without hold rcu_lock

[Peter Zijlstra]

On Mon, Apr 06, 2020 at 08:10:08PM +0800, Muchun Song wrote:
> The walk_tg_tree_from() caller must hold rcu_lock,

Not quite; with the RCU unification done 'recently' having preemption
disabled is sufficient. AFAICT preemption is disabled.

In fact; and I mentioned this to someone the other day, perhaps Joel; we
can go and delete a whole bunch of rcu_read_lock() from the scheduler --
basically undo all the work we did after RCU was split many years ago.