Commit 28728dd3 authored Jan 12, 2016 by Paul E. McKenney

rcu: Make expedited RCU-sched grace period immediately detect idle



Currently, sync_sched_exp_handler() will force a reschedule unless
this CPU has already checked in or unless a reschedule has already
been called for.  This is clearly wasteful if sync_sched_exp_handler()
interrupted an idle CPU, so this commit immediately reports the
quiescent state in that case.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

parent 274529ba

kernel/rcu/tree.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -3649,6 +3649,11 @@ static void sync_sched_exp_handler(void *data)
		if (!(READ_ONCE(rnp->expmask) & rdp->grpmask) \|\|
		__this_cpu_read(rcu_sched_data.cpu_no_qs.b.exp))
		return;
		if (rcu_is_cpu_rrupt_from_idle()) {
		rcu_report_exp_rdp(&rcu_sched_state,
		this_cpu_ptr(&rcu_sched_data), true);
		return;
		}
		__this_cpu_write(rcu_sched_data.cpu_no_qs.b.exp, true);
		resched_cpu(smp_processor_id());
		}