tracing: Let tracepoints have data passed to tracepoint callbacks
[linux-2.6.git] / include / linux / tracepoint.h
index 4353f3f..9a59d1f 100644 (file)
@@ -4,7 +4,7 @@
 /*
  * Kernel Tracepoint API.
  *
- * See Documentation/tracepoint.txt.
+ * See Documentation/trace/tracepoints.txt.
  *
  * (C) Copyright 2008 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
  *
 struct module;
 struct tracepoint;
 
+struct tracepoint_func {
+       void *func;
+       void *data;
+};
+
 struct tracepoint {
        const char *name;               /* Tracepoint name */
        int state;                      /* State. */
-       void **funcs;
+       void (*regfunc)(void);
+       void (*unregfunc)(void);
+       struct tracepoint_func *funcs;
 } __attribute__((aligned(32)));                /*
                                         * Aligned on 32 bytes because it is
                                         * globally visible and gcc happily
@@ -31,27 +38,99 @@ struct tracepoint {
                                         * Keep in sync with vmlinux.lds.h.
                                         */
 
+/*
+ * Connect a probe to a tracepoint.
+ * Internal API, should not be used directly.
+ */
+extern int tracepoint_probe_register(const char *name, void *probe, void *data);
+
+/*
+ * Disconnect a probe from a tracepoint.
+ * Internal API, should not be used directly.
+ */
+extern int
+tracepoint_probe_unregister(const char *name, void *probe, void *data);
+
+extern int tracepoint_probe_register_noupdate(const char *name, void *probe,
+                                             void *data);
+extern int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
+                                               void *data);
+extern void tracepoint_probe_update_all(void);
+
+struct tracepoint_iter {
+       struct module *module;
+       struct tracepoint *tracepoint;
+};
+
+extern void tracepoint_iter_start(struct tracepoint_iter *iter);
+extern void tracepoint_iter_next(struct tracepoint_iter *iter);
+extern void tracepoint_iter_stop(struct tracepoint_iter *iter);
+extern void tracepoint_iter_reset(struct tracepoint_iter *iter);
+extern int tracepoint_get_iter_range(struct tracepoint **tracepoint,
+       struct tracepoint *begin, struct tracepoint *end);
+
+/*
+ * tracepoint_synchronize_unregister must be called between the last tracepoint
+ * probe unregistration and the end of module exit to make sure there is no
+ * caller executing a probe when it is freed.
+ */
+static inline void tracepoint_synchronize_unregister(void)
+{
+       synchronize_sched();
+}
+
+#define PARAMS(args...) args
+
+#ifdef CONFIG_TRACEPOINTS
+extern void tracepoint_update_probe_range(struct tracepoint *begin,
+       struct tracepoint *end);
+#else
+static inline void tracepoint_update_probe_range(struct tracepoint *begin,
+       struct tracepoint *end)
+{ }
+#endif /* CONFIG_TRACEPOINTS */
+
+#endif /* _LINUX_TRACEPOINT_H */
+
+/*
+ * Note: we keep the TRACE_EVENT and DECLARE_TRACE outside the include
+ *  file ifdef protection.
+ *  This is due to the way trace events work. If a file includes two
+ *  trace event headers under one "CREATE_TRACE_POINTS" the first include
+ *  will override the TRACE_EVENT and break the second include.
+ */
+
 #ifndef DECLARE_TRACE
 
 #define TP_PROTO(args...)      args
-#define TP_ARGS(args...)               args
+#define TP_ARGS(args...)       args
 
 #ifdef CONFIG_TRACEPOINTS
 
 /*
  * it_func[0] is never NULL because there is at least one element in the array
  * when the array itself is non NULL.
+ *
+ * Note, the proto and args passed in includes "__data" as the first parameter.
+ * The reason for this is to handle the "void" prototype. If a tracepoint
+ * has a "void" prototype, then it is invalid to declare a function
+ * 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)                                    \
        do {                                                            \
-               void **it_func;                                         \
+               struct tracepoint_func *it_func_ptr;                    \
+               void *it_func;                                          \
+               void *__data;                                           \
                                                                        \
                rcu_read_lock_sched_notrace();                          \
-               it_func = rcu_dereference((tp)->funcs);                 \
-               if (it_func) {                                          \
+               it_func_ptr = rcu_dereference_sched((tp)->funcs);       \
+               if (it_func_ptr) {                                      \
                        do {                                            \
-                               ((void(*)(proto))(*it_func))(args);     \
-                       } while (*(++it_func));                         \
+                               it_func = (it_func_ptr)->func;          \
+                               __data = (it_func_ptr)->data;           \
+                               ((void(*)(proto))(it_func))(args);      \
+                       } while ((++it_func_ptr)->func);                \
                }                                                       \
                rcu_read_unlock_sched_notrace();                        \
        } while (0)
@@ -61,107 +140,97 @@ struct tracepoint {
  * 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)                               \
+#define __DECLARE_TRACE(name, proto, args, data_proto, data_args)      \
        extern struct tracepoint __tracepoint_##name;                   \
        static inline void trace_##name(proto)                          \
        {                                                               \
                if (unlikely(__tracepoint_##name.state))                \
                        __DO_TRACE(&__tracepoint_##name,                \
-                               TP_PROTO(proto), TP_ARGS(args));        \
+                               TP_PROTO(data_proto),                   \
+                               TP_ARGS(data_args));                    \
        }                                                               \
-       static inline int register_trace_##name(void (*probe)(proto))   \
+       static inline int                                               \
+       register_trace_##name(void (*probe)(data_proto), void *data)    \
        {                                                               \
-               return tracepoint_probe_register(#name, (void *)probe); \
+               return tracepoint_probe_register(#name, (void *)probe,  \
+                                                data);                 \
        }                                                               \
-       static inline int unregister_trace_##name(void (*probe)(proto)) \
+       static inline int                                               \
+       unregister_trace_##name(void (*probe)(data_proto), void *data)  \
+       {                                                               \
+               return tracepoint_probe_unregister(#name, (void *)probe, \
+                                                  data);               \
+       }                                                               \
+       static inline void                                              \
+       check_trace_callback_type_##name(void (*cb)(data_proto))        \
        {                                                               \
-               return tracepoint_probe_unregister(#name, (void *)probe);\
        }
 
-#define DEFINE_TRACE(name)                                             \
+#define DEFINE_TRACE_FN(name, reg, unreg)                              \
        static const char __tpstrtab_##name[]                           \
        __attribute__((section("__tracepoints_strings"))) = #name;      \
        struct tracepoint __tracepoint_##name                           \
        __attribute__((section("__tracepoints"), aligned(32))) =        \
-               { __tpstrtab_##name, 0, NULL }
+               { __tpstrtab_##name, 0, reg, unreg, NULL }
+
+#define DEFINE_TRACE(name)                                             \
+       DEFINE_TRACE_FN(name, NULL, NULL);
 
 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)                             \
        EXPORT_SYMBOL_GPL(__tracepoint_##name)
 #define EXPORT_TRACEPOINT_SYMBOL(name)                                 \
        EXPORT_SYMBOL(__tracepoint_##name)
 
-extern void tracepoint_update_probe_range(struct tracepoint *begin,
-       struct tracepoint *end);
-
 #else /* !CONFIG_TRACEPOINTS */
-#define DECLARE_TRACE(name, proto, args)                               \
-       static inline void _do_trace_##name(struct tracepoint *tp, proto) \
-       { }                                                             \
+#define __DECLARE_TRACE(name, proto, args, data_proto, data_args)      \
        static inline void trace_##name(proto)                          \
        { }                                                             \
-       static inline int register_trace_##name(void (*probe)(proto))   \
+       static inline int                                               \
+       register_trace_##name(void (*probe)(data_proto),                \
+                             void *data)                               \
        {                                                               \
                return -ENOSYS;                                         \
        }                                                               \
-       static inline int unregister_trace_##name(void (*probe)(proto)) \
+       static inline int                                               \
+       unregister_trace_##name(void (*probe)(data_proto),              \
+                               void *data)                             \
        {                                                               \
                return -ENOSYS;                                         \
+       }                                                               \
+       static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
+       {                                                               \
        }
 
+#define DEFINE_TRACE_FN(name, reg, unreg)
 #define DEFINE_TRACE(name)
 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 #define EXPORT_TRACEPOINT_SYMBOL(name)
 
-static inline void tracepoint_update_probe_range(struct tracepoint *begin,
-       struct tracepoint *end)
-{ }
 #endif /* CONFIG_TRACEPOINTS */
-#endif /* DECLARE_TRACE */
-
-/*
- * Connect a probe to a tracepoint.
- * Internal API, should not be used directly.
- */
-extern int tracepoint_probe_register(const char *name, void *probe);
 
 /*
- * Disconnect a probe from a tracepoint.
- * Internal API, should not be used directly.
- */
-extern int tracepoint_probe_unregister(const char *name, void *probe);
-
-extern int tracepoint_probe_register_noupdate(const char *name, void *probe);
-extern int tracepoint_probe_unregister_noupdate(const char *name, void *probe);
-extern void tracepoint_probe_update_all(void);
-
-struct tracepoint_iter {
-       struct module *module;
-       struct tracepoint *tracepoint;
-};
-
-extern void tracepoint_iter_start(struct tracepoint_iter *iter);
-extern void tracepoint_iter_next(struct tracepoint_iter *iter);
-extern void tracepoint_iter_stop(struct tracepoint_iter *iter);
-extern void tracepoint_iter_reset(struct tracepoint_iter *iter);
-extern int tracepoint_get_iter_range(struct tracepoint **tracepoint,
-       struct tracepoint *begin, struct tracepoint *end);
-
-/*
- * tracepoint_synchronize_unregister must be called between the last tracepoint
- * probe unregistration and the end of module exit to make sure there is no
- * caller executing a probe when it is freed.
+ * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype
+ * (void). "void" is a special value in a function prototype and can
+ * not be combined with other arguments. Since the DECLARE_TRACE()
+ * macro adds a data element at the beginning of the prototype,
+ * we need a way to differentiate "(void *data, proto)" from
+ * "(void *data, void)". The second prototype is invalid.
+ *
+ * DECLARE_TRACE_NOARGS() passes "void" as the tracepoint prototype
+ * and "void *__data" as the callback prototype.
+ *
+ * DECLARE_TRACE() passes "proto" as the tracepoint protoype and
+ * "void *__data, proto" as the callback prototype.
  */
-static inline void tracepoint_synchronize_unregister(void)
-{
-       synchronize_sched();
-}
+#define DECLARE_TRACE_NOARGS(name)                                     \
+               __DECLARE_TRACE(name, void, , void *__data, __data)
 
-#define PARAMS(args...) args
+#define DECLARE_TRACE(name, proto, args)                               \
+               __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),      \
+                               PARAMS(void *__data, proto),            \
+                               PARAMS(__data, args))
 
-#ifndef TRACE_FORMAT
-#define TRACE_FORMAT(name, proto, args, fmt)           \
-       DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
-#endif
+#endif /* DECLARE_TRACE */
 
 #ifndef TRACE_EVENT
 /*
@@ -203,7 +272,7 @@ static inline void tracepoint_synchronize_unregister(void)
  *     * This is how the trace record is structured and will
  *     * be saved into the ring buffer. These are the fields
  *     * that will be exposed to user-space in
- *     * /debug/tracing/events/<*>/format.
+ *     * /sys/kernel/debug/tracing/events/<*>/format.
  *     *
  *     * The declared 'local variable' is called '__entry'
  *     *
@@ -263,11 +332,22 @@ static inline void tracepoint_synchronize_unregister(void)
  * tracepoint callback (this is used by programmatic plugins and
  * can also by used by generic instrumentation like SystemTap), and
  * it is also used to expose a structured trace record in
- * /debug/tracing/events/.
+ * /sys/kernel/debug/tracing/events/.
+ *
+ * A set of (un)registration functions can be passed to the variant
+ * TRACE_EVENT_FN to perform any (un)registration work.
  */
 
+#define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
+#define DEFINE_EVENT(template, name, proto, args)              \
+       DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
+#define DEFINE_EVENT_PRINT(template, name, proto, args, print) \
+       DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
+
 #define TRACE_EVENT(name, proto, args, struct, assign, print)  \
        DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
-#endif
+#define TRACE_EVENT_FN(name, proto, args, struct,              \
+               assign, print, reg, unreg)                      \
+       DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 
-#endif
+#endif /* ifdef TRACE_EVENT (see note above) */