Messages in this thread | | | Date | Tue, 21 Apr 2020 18:24:52 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] sched/fair: Fix call walk_tg_tree_from() without hold rcu_lock |
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On Tue, Apr 21, 2020 at 08:43:12AM -0700, Paul E. McKenney wrote: > On Tue, Apr 21, 2020 at 03:52:58PM +0200, Peter Zijlstra wrote: > > 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. > > "If only I knew then what I know now..." > > Then again, I suspect that we all have ample opportunity to use that > particular old phrase. ;-)
Quite so; I'm just fearing that rcu-lockdep annotation stuff. IIRC that doesn't (nor can it, in general) consider the implicit preempt-disable from locks and such for !PREEMPT builds.
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