tracing/rcu: Add trace_##name##__rcuidle() static tracepoint for inside rcu_idle_exit() sections

Added is a new static inline function that lets *any* tracepoint be used
inside a rcu_idle_exit() section. And this also solves the problem where
the same tracepoint may be used inside a rcu_idle_exit() section as well
as outside of one.

I added a new tracepoint function with a "_rcuidle" extension. All
tracepoints can be used with either the normal "trace_foobar()"
function, or the "trace_foobar_rcuidle()" function when inside a
rcu_idle_exit() section.

All tracepoints defined by TRACE_EVENT() or any of the derivatives
will have a "_rcuidle()" function also defined. When a tracepoint is
used within an rcu_idle_exit() section, the "_rcuidle()" version must
be used. This denotes that the tracepoint is within rcu_idle_exit()
and it allows the rcu read locks within the tracepoint to still
be valid, as this version takes us out of rcu_idle_exit().

Another nice aspect about this patch is that "static inline"s are not
compiled into text when not used. So only the tracepoints that actually
use the _rcuidle() version will have them defined in the actual text
that is booted.

Link: http://lkml.kernel.org/r/1328563113.2200.39.camel@gandalf.stny.rr.com>

Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 18 insertions, 4 deletions

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index df0a779c1bbd..fc36da97ff7e 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -114,7 +114,7 @@ static inline void tracepoint_synchronize_unregister(void)
  * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
  * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
  */
-#define __DO_TRACE(tp, proto, args, cond)                               \
+#define __DO_TRACE(tp, proto, args, cond, prercu, postrcu)              \
         do {                                                            \
                 struct tracepoint_func *it_func_ptr;                    \
                 void *it_func;                                          \
@@ -122,6 +122,7 @@ static inline void tracepoint_synchronize_unregister(void)
                                                                         \
                 if (!(cond))                                            \
                         return;                                         \
+                prercu;                                                 \
                 rcu_read_lock_sched_notrace();                          \
                 it_func_ptr = rcu_dereference_sched((tp)->funcs);       \
                 if (it_func_ptr) {                                      \
@@ -132,6 +133,7 @@ static inline void tracepoint_synchronize_unregister(void)
                         } while ((++it_func_ptr)->func);                \
                 }                                                       \
                 rcu_read_unlock_sched_notrace();                        \
+                postrcu;                                                \
         } while (0)
 
 /*
@@ -139,7 +141,7 @@ static inline void tracepoint_synchronize_unregister(void)
  * not add unwanted padding between the beginning of the section and the
  * structure. Force alignment to the same alignment as the section start.
  */
-#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
+#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
         extern struct tracepoint __tracepoint_##name;                   \
         static inline void trace_##name(proto)                          \
         {                                                               \
@@ -147,7 +149,17 @@ static inline void tracepoint_synchronize_unregister(void)
                         __DO_TRACE(&__tracepoint_##name,                \
                                 TP_PROTO(data_proto),                   \
                                 TP_ARGS(data_args),                     \
-                                TP_CONDITION(cond));                    \
+                                TP_CONDITION(cond),,);                  \
+        }                                                               \
+        static inline void trace_##name##_rcuidle(proto)                \
+        {                                                               \
+                if (static_branch(&__tracepoint_##name.key))            \
+                        __DO_TRACE(&__tracepoint_##name,                \
+                                TP_PROTO(data_proto),                   \
+                                TP_ARGS(data_args),                     \
+                                TP_CONDITION(cond),                     \
+                                rcu_idle_exit(),                        \
+                                rcu_idle_enter());                      \
         }                                                               \
         static inline int                                               \
         register_trace_##name(void (*probe)(data_proto), void *data)    \
@@ -190,9 +202,11 @@ static inline void tracepoint_synchronize_unregister(void)
         EXPORT_SYMBOL(__tracepoint_##name)
 
 #else /* !CONFIG_TRACEPOINTS */
-#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
+#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
         static inline void trace_##name(proto)                          \
         { }                                                             \
+        static inline void trace_##name##_rcuidle(proto)                \
+        { }                                                             \
         static inline int                                               \
         register_trace_##name(void (*probe)(data_proto),                \
                               void *data)                               \