markers: create DEFINE_MARKER and GET_MARKER (new API)

Impact: new API.

Allow markers to be used only for declaration, without function call
associated. Useful to create specialized probes.

The problem we had is that two function calls were required when one
wanted to put a marker in a tracepoint probe. Now the marker can be used
simply for trace data type declaration, leaving the trace write work
within the tracepoint probe without any additional function call.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/Documentation/markers.txt b/Documentation/markers.txt
index 089f6138fcd94249a6444ca3a932a50c263098e1..6d275e4ef385d71acc6a931cc59fb5e9dfdf4eb0 100644 (file)
--- a/Documentation/markers.txt
+++ b/Documentation/markers.txt
@@ -70,6 +70,20 @@ a printk warning which identifies the inconsistency:
 
 "Format mismatch for probe probe_name (format), marker (format)"
 
+Another way to use markers is to simply define the marker without generating any
+function call to actually call into the marker. This is useful in combination
+with tracepoint probes in a scheme like this :
+
+void probe_tracepoint_name(unsigned int arg1, struct task_struct *tsk);
+
+DEFINE_MARKER_TP(marker_eventname, tracepoint_name, probe_tracepoint_name,
+       "arg1 %u pid %d");
+
+notrace void probe_tracepoint_name(unsigned int arg1, struct task_struct *tsk)
+{
+       struct marker *marker = &GET_MARKER(kernel_irq_entry);
+       /* write data to trace buffers ... */
+}
 
 * Probe / marker example
 

diff --git a/include/linux/marker.h b/include/linux/marker.h
index 57a307018cebb102f12a7326580e166a151be336..34c14bc957f5b7a1f41cab2825ae9d0f4ad16e84 100644 (file)
--- a/include/linux/marker.h
+++ b/include/linux/marker.h
@@ -55,6 +55,22 @@ struct marker {
 
 #ifdef CONFIG_MARKERS
 
+#define _DEFINE_MARKER(name, tp_name_str, tp_cb, format)               \
+               static const char __mstrtab_##name[]                    \
+               __attribute__((section("__markers_strings")))           \
+               = #name "\0" format;                                    \
+               static struct marker __mark_##name                      \
+               __attribute__((section("__markers"), aligned(8))) =     \
+               { __mstrtab_##name, &__mstrtab_##name[sizeof(#name)],   \
+                 0, 0, marker_probe_cb, { __mark_empty_function, NULL},\
+                 NULL, tp_name_str, tp_cb }
+
+#define DEFINE_MARKER(name, format)                                    \
+               _DEFINE_MARKER(name, NULL, NULL, format)
+
+#define DEFINE_MARKER_TP(name, tp_name, tp_cb, format)                 \
+               _DEFINE_MARKER(name, #tp_name, tp_cb, format)
+
 /*
  * Note : the empty asm volatile with read constraint is used here instead of a
  * "used" attribute to fix a gcc 4.1.x bug.
@@ -68,14 +84,7 @@ struct marker {
  */
 #define __trace_mark(generic, name, call_private, format, args...)     \
        do {                                                            \
-               static const char __mstrtab_##name[]                    \
-               __attribute__((section("__markers_strings")))           \
-               = #name "\0" format;                                    \
-               static struct marker __mark_##name                      \
-               __attribute__((section("__markers"), aligned(8))) =     \
-               { __mstrtab_##name, &__mstrtab_##name[sizeof(#name)],   \
-               0, 0, marker_probe_cb,                                  \
-               { __mark_empty_function, NULL}, NULL, NULL, NULL };     \
+               DEFINE_MARKER(name, format);                            \
                __mark_check_format(format, ## args);                   \
                if (unlikely(__mark_##name.state)) {                    \
                        (*__mark_##name.call)                           \
@@ -89,14 +98,7 @@ struct marker {
                {                                                       \
                        register_trace_##tp_name(tp_cb);                \
                }                                                       \
-               static const char __mstrtab_##name[]                    \
-               __attribute__((section("__markers_strings")))           \
-               = #name "\0" format;                                    \
-               static struct marker __mark_##name                      \
-               __attribute__((section("__markers"), aligned(8))) =     \
-               { __mstrtab_##name, &__mstrtab_##name[sizeof(#name)],   \
-               0, 0, marker_probe_cb,                                  \
-               { __mark_empty_function, NULL}, NULL, #tp_name, tp_cb };\
+               DEFINE_MARKER_TP(name, tp_name, tp_cb, format);         \
                __mark_check_format(format, ## args);                   \
                (*__mark_##name.call)(&__mark_##name, call_private,     \
                                        ## args);                       \
@@ -104,7 +106,11 @@ struct marker {
 
 extern void marker_update_probe_range(struct marker *begin,
        struct marker *end);
+
+#define GET_MARKER(name)       (__mark_##name)
+
 #else /* !CONFIG_MARKERS */
+#define DEFINE_MARKER(name, tp_name, tp_cb, format)
 #define __trace_mark(generic, name, call_private, format, args...) \
                __mark_check_format(format, ## args)
 #define __trace_mark_tp(name, call_private, tp_name, tp_cb, format, args...) \
@@ -118,6 +124,7 @@ extern void marker_update_probe_range(struct marker *begin,
 static inline void marker_update_probe_range(struct marker *begin,
        struct marker *end)
 { }
+#define GET_MARKER(name)
 #endif /* CONFIG_MARKERS */
 
 /**