rcu: Hold off RCU_FAST_NO_HZ after timer posted

This commit handles workloads that transition quickly between idle and
non-idle, and where the CPU's callbacks cannot be invoked, but where
RCU does not have anything immediate for the CPU to do.  Without this
patch, the RCU_FAST_NO_HZ code can be invoked repeatedly on each entry
to idle.  The commit sets the per-CPU rcu_dyntick_holdoff variable to
hold off further attempts for a tick.

Reported-by: "Abou Gazala, Neven M" <neven.m.abou.gazala@intel.com>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 392a65136a72..c023464816be 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -2138,7 +2138,7 @@ static void rcu_prepare_for_idle(int cpu)
                 /* Can we go dyntick-idle despite still having callbacks? */
                 trace_rcu_prep_idle("Dyntick with callbacks");
                 per_cpu(rcu_dyntick_drain, cpu) = 0;
-                per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1;
+                per_cpu(rcu_dyntick_holdoff, cpu) = jiffies;
                 if (rcu_cpu_has_nonlazy_callbacks(cpu))
                         hrtimer_start(&per_cpu(rcu_idle_gp_timer, cpu),
                                       rcu_idle_gp_wait, HRTIMER_MODE_REL);