On Tue, Oct 28, 2014 at 03:22:58PM -0700, Paul E. McKenney wrote: > From: "Paul E. McKenney" <[email protected]> > > Currently, synchronize_sched_expedited() sends IPIs to all online CPUs, > even those that are idle or executing in nohz_full= userspace. Because > idle CPUs and nohz_full= userspace CPUs are in extended quiescent states, > there is no need to IPI them in the first place. This commit therefore > avoids IPIing CPUs that are already in extended quiescent states. > > Signed-off-by: Paul E. McKenney <[email protected]> > --- > kernel/rcu/tree.c | 27 ++++++++++++++++++++++++++- > 1 file changed, 26 insertions(+), 1 deletion(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 7f73c5edf8cf..9e3c20f117cd 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -2950,6 +2950,9 @@ static int synchronize_sched_expedited_cpu_stop(void > *data) > */ > void synchronize_sched_expedited(void) > { > + cpumask_var_t cm; > + bool cma = false; > + int cpu; > long firstsnap, s, snap; > int trycount = 0; > struct rcu_state *rsp = &rcu_sched_state; > @@ -2984,11 +2987,26 @@ void synchronize_sched_expedited(void) > } > WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id())); > > + /* Offline CPUs, idle CPUs, and any CPU we run on are quiescent. */ > + cma = zalloc_cpumask_var(&cm, GFP_KERNEL); > + if (cma) { > + cpumask_copy(cm, cpu_online_mask); > + cpumask_clear_cpu(raw_smp_processor_id(), cm); > + for_each_cpu(cpu, cm) { > + struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); > + > + if (!(atomic_add_return(0, &rdtp->dynticks) & 0x1)) > + cpumask_clear_cpu(cpu, cm); > + } > + if (cpumask_weight(cm) == 0) > + goto all_cpus_idle; > + }
Is there a reason not to use on_each_cpu_cond()? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
