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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-04-11 01:40:35 +0300
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-06-08 18:25:22 +0300
commitf92c734f02cbf10e40569facff82059ae9b61920 (patch)
tree95d64d71c63d840d31bef62793ce8262305a6f1e /include/trace/events
parentc0ee4500ff67e455dcbc74ff3e9e9faa3bc93be1 (diff)
downloadlinux-f92c734f02cbf10e40569facff82059ae9b61920.tar.xz
rcu: Prevent rcu_barrier() from starting needless grace periods
Currently rcu_barrier() uses call_rcu() to enqueue new callbacks on each CPU with a non-empty callback list. This works, but means that rcu_barrier() forces grace periods that are not otherwise needed. The key point is that rcu_barrier() never needs to wait for a grace period, but instead only for all pre-existing callbacks to be invoked. This means that rcu_barrier()'s new callbacks should be placed in the callback-list segment containing the last pre-existing callback. This commit makes this change using the new rcu_segcblist_entrain() function. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'include/trace/events')
-rw-r--r--include/trace/events/rcu.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index e3facb356838..91dc089d65b7 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -742,6 +742,7 @@ TRACE_EVENT(rcu_torture_read,
* "OnlineQ": _rcu_barrier() found online CPU with callbacks.
* "OnlineNQ": _rcu_barrier() found online CPU, no callbacks.
* "IRQ": An rcu_barrier_callback() callback posted on remote CPU.
+ * "IRQNQ": An rcu_barrier_callback() callback found no callbacks.
* "CB": An rcu_barrier_callback() invoked a callback, not the last.
* "LastCB": An rcu_barrier_callback() invoked the last callback.
* "Inc2": _rcu_barrier() piggyback check counter incremented.