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

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>

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index df0a779..fc36da9 100644 (file)
--- 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)                               \