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>