tracing: Add DECLARE_TRACE_WITH_CALLBACK() macro

Introduce a new 'DECLARE_TRACE_WITH_CALLBACK()' macro, so that
tracepoints can associate an external register/unregister function.

This prepares for the syscalls tracer conversion to trace events. We
will need to perform arch level operations once a syscall event is
turned on/off, such as TIF flags setting, hence the need of such
specific callbacks.

Signed-off-by: Jason Baron <jbaron@redhat.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Jiaying Zhang <jiayingz@google.com>
Cc: Martin Bligh <mbligh@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

1 files changed, 27 insertions, 4 deletions

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index b9dc4ca0246f..5984ed04c03b 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -60,8 +60,10 @@ struct tracepoint {
  * Make sure the alignment of the structure in the __tracepoints section will
  * not add unwanted padding between the beginning of the section and the
  * structure. Force alignment to the same alignment as the section start.
+ * An optional set of (un)registration functions can be passed to perform any
+ * additional (un)registration work.
  */
-#define DECLARE_TRACE(name, proto, args)                                \
+#define DECLARE_TRACE_WITH_CALLBACK(name, proto, args, reg, unreg)      \
         extern struct tracepoint __tracepoint_##name;                   \
         static inline void trace_##name(proto)                          \
         {                                                               \
@@ -71,13 +73,30 @@ struct tracepoint {
         }                                                               \
         static inline int register_trace_##name(void (*probe)(proto))   \
         {                                                               \
-                return tracepoint_probe_register(#name, (void *)probe); \
+                int ret;                                                \
+                void (*func)(void) = reg;                               \
+                                                                        \
+                ret = tracepoint_probe_register(#name, (void *)probe);  \
+                if (func && !ret)                                       \
+                        func();                                         \
+                return ret;                                             \
         }                                                               \
         static inline int unregister_trace_##name(void (*probe)(proto)) \
         {                                                               \
-                return tracepoint_probe_unregister(#name, (void *)probe);\
+                int ret;                                                \
+                void (*func)(void) = unreg;                             \
+                                                                        \
+                ret = tracepoint_probe_unregister(#name, (void *)probe);\
+                if (func && !ret)                                       \
+                        func();                                         \
+                return ret;                                             \
         }
 
+
+#define DECLARE_TRACE(name, proto, args)                                 \
+        DECLARE_TRACE_WITH_CALLBACK(name, TP_PROTO(proto), TP_ARGS(args),\
+                                        NULL, NULL);
+
 #define DEFINE_TRACE(name)                                              \
         static const char __tpstrtab_##name[]                           \
         __attribute__((section("__tracepoints_strings"))) = #name;      \
@@ -94,7 +113,7 @@ extern void tracepoint_update_probe_range(struct tracepoint *begin,
         struct tracepoint *end);
 
 #else /* !CONFIG_TRACEPOINTS */
-#define DECLARE_TRACE(name, proto, args)                                \
+#define DECLARE_TRACE_WITH_CALLBACK(name, proto, args, reg, unreg)      \
         static inline void _do_trace_##name(struct tracepoint *tp, proto) \
         { }                                                             \
         static inline void trace_##name(proto)                          \
@@ -108,6 +127,10 @@ extern void tracepoint_update_probe_range(struct tracepoint *begin,
                 return -ENOSYS;                                         \
         }
 
+#define DECLARE_TRACE(name, proto, args)                                 \
+        DECLARE_TRACE_WITH_CALLBACK(name, TP_PROTO(proto), TP_ARGS(args),\
+                                        NULL, NULL);
+
 #define DEFINE_TRACE(name)
 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 #define EXPORT_TRACEPOINT_SYMBOL(name)