On Mon, 2018-07-09 at 15:08 -0700, Paul E. McKenney wrote:
> index f9c0ca2ccf0c..3350ece366ab 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -2839,6 +2839,15 @@ void rcu_check_callbacks(int user)
> rcu_bh_qs();
> }
> rcu_preempt_check_callbacks();
> + /* The load-acquire pairs with the store-release setting to true. */
> + if (smp_load_acquire(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs))) {
> + /* Idle and userspace execution already are quiescent states.
> */
> + if (rcu_is_cpu_rrupt_from_idle() && !user) {if (idle && !user) seems tautological and... illogical. If I make it 'if (!rcu_is_cpu_rrput_from_idle() && !user)' it seems to work better. Ripping out my debugging printks now to check that's still true... (Also, isn't userspace execution only a quiescent state if NO_HZ_FULL?) > + set_tsk_need_resched(current); > + set_preempt_need_resched(); > + } > + __this_cpu_write(rcu_dynticks.rcu_urgent_qs, false); > + }
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