rcu: reduce the number of spurious RCU_SOFTIRQ invocations

[safe/jmp/linux-2.6] / kernel / rcutree.c

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index c60fd74..ba69969 100644 (file)
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1161,8 +1161,6 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
  */
 void rcu_check_callbacks(int cpu, int user)
 {
-       if (!rcu_pending(cpu))
-               return; /* if nothing for RCU to do. */
        if (user ||
            (idle_cpu(cpu) && rcu_scheduler_active &&
             !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
@@ -1194,7 +1192,8 @@ void rcu_check_callbacks(int cpu, int user)
                rcu_bh_qs(cpu);
        }
        rcu_preempt_check_callbacks(cpu);
-       raise_softirq(RCU_SOFTIRQ);
+       if (rcu_pending(cpu))
+               raise_softirq(RCU_SOFTIRQ);
 }
 
 #ifdef CONFIG_SMP
@@ -1534,18 +1533,20 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
        check_cpu_stall(rsp, rdp);
 
        /* Is the RCU core waiting for a quiescent state from this CPU? */
-       if (rdp->qs_pending) {
+       if (rdp->qs_pending && !rdp->passed_quiesc) {
 
                /*
                 * If force_quiescent_state() coming soon and this CPU
                 * needs a quiescent state, and this is either RCU-sched
                 * or RCU-bh, force a local reschedule.
                 */
+               rdp->n_rp_qs_pending++;
                if (!rdp->preemptable &&
                    ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1,
                                 jiffies))
                        set_need_resched();
-               rdp->n_rp_qs_pending++;
+       } else if (rdp->qs_pending && rdp->passed_quiesc) {
+               rdp->n_rp_report_qs++;
                return 1;
        }