The idea behind the checks for extended quiescent states at the end of __call_rcu_nocb() is to handle cases where call_rcu() is invoked directly from within an extended quiescent state, for example, from the idle loop. However, this will result in a timer-mediated deferred wakeup, which will cause the needed wakeup to happen within a jiffy or thereabouts. There should be no forward-progress concerns, and if there are, the proper response is to exit the extended quiescent state while executing the endless blast of call_rcu() invocations, for example, using RCU_NONIDLE(). Given the more realistic case of an isolated call_rcu() invocation, there should be no problem. This commit therefore removes the checks for invoking call_rcu() within an extended quiescent state for on no-CBs CPUs. Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxx> --- kernel/rcu/tree_plugin.h | 10 ---------- 1 file changed, 10 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index fc6133eed50a..9936a66b80bb 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1709,16 +1709,6 @@ static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, -atomic_long_read(&rdp->nocb_q_count_lazy), -rcu_get_n_cbs_nocb_cpu(rdp)); - /* - * If called from an extended quiescent state with interrupts - * disabled, invoke the RCU core in order to allow the idle-entry - * deferred-wakeup check to function. - */ - if (irqs_disabled_flags(flags) && - !rcu_is_watching() && - cpu_online(smp_processor_id())) - invoke_rcu_core(); - return true; } -- 2.17.1
