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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2018-05-12 17:42:20 +0300
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2018-07-13 01:38:52 +0300
commita2165e416878b325747f871df4b236b49bf61486 (patch)
treef34e198b527f5a69380b72a311076e1f26e26268 /include/trace/events
parente1333462e3cf933ab860c693ef1ff50775c7ea7f (diff)
downloadlinux-a2165e416878b325747f871df4b236b49bf61486.tar.xz
rcu: Don't funnel-lock above leaf node if GP in progress
The old grace-period start code would acquire only the leaf's rcu_node structure's ->lock if that structure believed that a grace period was in progress. The new code advances to the leaf's parent in this case, needlessly acquiring then leaf's parent's ->lock. This commit therefore checks the grace-period state after marking the leaf with the need for the specified grace period, and if the leaf believes that a grace period is in progress, takes an early exit. Reported-by: Joel Fernandes <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Add "Startedleaf" tracing as suggested by Joel Fernandes. ]
Diffstat (limited to 'include/trace/events')
-rw-r--r--include/trace/events/rcu.h4
1 files changed, 2 insertions, 2 deletions
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index 7d3650cc9d30..5ab1df0a2801 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -91,8 +91,8 @@ TRACE_EVENT(rcu_grace_period,
*
* "Startleaf": Request a grace period based on leaf-node data.
* "Prestarted": Someone beat us to the request
- * "Startedleaf": Leaf-node start proved sufficient.
- * "Startedleafroot": Leaf-node start proved sufficient after checking root.
+ * "Startedleaf": Leaf node marked for future GP.
+ * "Startedleafroot": All nodes from leaf to root marked for future GP.
* "Startedroot": Requested a nocb grace period based on root-node data.
* "NoGPkthread": The RCU grace-period kthread has not yet started.
* "StartWait": Start waiting for the requested grace period.