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Subject[PATCH 1/3][RFC] tracing/rcu: Add trace_##name##__rcuidle() static tracepoint for inside rcu_idle_exit() sections
From: Steven Rostedt <srostedt@redhat.com>

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>
---
include/linux/tracepoint.h | 20 ++++++++++++++++----
1 files changed, 16 insertions(+), 4 deletions(-)
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index df0a779..00d073a 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) \
@@ -190,7 +202,7 @@ 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 int \
--
1.7.8.3



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