Messages in this thread | | | Date | Tue, 3 Sep 2019 09:47:18 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 2/3] task: RCU protect tasks on the runqueue |
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On Tue, Sep 03, 2019 at 09:41:17AM +0200, Peter Zijlstra wrote: > On Mon, Sep 02, 2019 at 11:52:01PM -0500, Eric W. Biederman wrote: > > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > > index 2b037f195473..802958407369 100644 > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > > @@ -3857,7 +3857,7 @@ static void __sched notrace __schedule(bool preempt) > > > > if (likely(prev != next)) { > > rq->nr_switches++; > > - rq->curr = next; > > + rcu_assign_pointer(rq->curr, next); > > /* > > * The membarrier system call requires each architecture > > * to have a full memory barrier after updating > > This one is sad; it puts a (potentially) expensive barrier in here. And > I'm not sure I can explain the need for it. That is, we've not changed > @next before this and don't need to 'publish' it as such. > > Can we use RCU_INIT_POINTER() or simply WRITE_ONCE(), here?
That is, I'm thinking we qualify for point 3 (both a and b) of RCU_INIT_POINTER().
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