tree 70a58702194588fa0773463523f72c682785d040
parent 0bb7b59d6e2b8440cd7097097dd4bbfc4d76ed07
author Paul E. McKenney <paul.mckenney@linaro.org> 1325887890 -0800
committer Paul E. McKenney <paulmck@linux.vnet.ibm.com> 1329843805 -0800

rcu: Avoid waking up CPUs having only kfree_rcu() callbacks

When CONFIG_RCU_FAST_NO_HZ is enabled, RCU will allow a given CPU to
enter dyntick-idle mode even if it still has RCU callbacks queued.
RCU avoids system hangs in this case by scheduling a timer for several
jiffies in the future.  However, if all of the callbacks on that CPU
are from kfree_rcu(), there is no reason to wake the CPU up, as it is
not a problem to defer freeing of memory.

This commit therefore tracks the number of callbacks on a given CPU
that are from kfree_rcu(), and avoids scheduling the timer if all of
a given CPU's callbacks are from kfree_rcu().

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