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authorSteven Rostedt <rostedt@goodmis.org>2013-05-28 14:38:42 -0400
committerSteven Rostedt <rostedt@goodmis.org>2013-05-28 22:47:13 -0400
commit12bcbe66d7b3cc9f9f86cd02f925666eaa3c2107 (patch)
tree54e70e0f7450aedfee1418742758dc538d9649e5 /include/linux/rcupdate.h
parent6721cb60022629ae76365551f05d9658b8d14c55 (diff)
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rcu: Add _notrace variation of rcu_dereference_raw() and hlist_for_each_entry_rcu()
As rcu_dereference_raw() under RCU debug config options can add quite a bit of checks, and that tracing uses rcu_dereference_raw(), these checks happen with the function tracer. The function tracer also happens to trace these debug checks too. This added overhead can livelock the system. Add a new interface to RCU for both rcu_dereference_raw_notrace() as well as hlist_for_each_entry_rcu_notrace() as the hlist iterator uses the rcu_dereference_raw() as well, and is used a bit with the function tracer. Link: http://lkml.kernel.org/r/20130528184209.304356745@goodmis.org Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'include/linux/rcupdate.h')
-rw-r--r--include/linux/rcupdate.h9
1 files changed, 9 insertions, 0 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 4ccd68e..ddcc782 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -640,6 +640,15 @@ static inline void rcu_preempt_sleep_check(void)
#define rcu_dereference_raw(p) rcu_dereference_check(p, 1) /*@@@ needed? @@@*/
+/*
+ * The tracing infrastructure traces RCU (we want that), but unfortunately
+ * some of the RCU checks causes tracing to lock up the system.
+ *
+ * The tracing version of rcu_dereference_raw() must not call
+ * rcu_read_lock_held().
+ */
+#define rcu_dereference_raw_notrace(p) __rcu_dereference_check((p), 1, __rcu)
+
/**
* rcu_access_index() - fetch RCU index with no dereferencing
* @p: The index to read
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