tracepoint: Give priority to probes of tracepoints
In order to guarantee that a probe will be called before other probes that
are attached to a tracepoint, there needs to be a mechanism to provide
priority of one probe over the others.
Adding a prio field to the struct tracepoint_func, which lets the probes be
sorted by the priority set in the structure. If no priority is specified,
then a priority of 10 is given (this is a macro, and perhaps may be changed
in the future).
Now probes may be added to affect other probes that are attached to a
tracepoint with a guaranteed order.
One use case would be to allow tracing of tracepoints be able to filter by
pid. A special (higher priority probe) may be added to the sched_switch
tracepoint and set the necessary flags of the other tracepoints to notify
them if they should be traced or not. In case a tracepoint is enabled at the
sched_switch tracepoint too, the order of the two are not random.
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index afada36..6b79537 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -26,6 +26,7 @@
struct tracepoint_func {
void *func;
void *data;
+ int prio;
};
struct tracepoint {
@@ -42,9 +43,14 @@
unsigned long enum_value;
};
+#define TRACEPOINT_DEFAULT_PRIO 10
+
extern int
tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data);
extern int
+tracepoint_probe_register_prio(struct tracepoint *tp, void *probe, void *data,
+ int prio);
+extern int
tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data);
extern void
for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
@@ -207,6 +213,13 @@
(void *)probe, data); \
} \
static inline int \
+ register_trace_prio_##name(void (*probe)(data_proto), void *data,\
+ int prio) \
+ { \
+ return tracepoint_probe_register_prio(&__tracepoint_##name, \
+ (void *)probe, data, prio); \
+ } \
+ static inline int \
unregister_trace_##name(void (*probe)(data_proto), void *data) \
{ \
return tracepoint_probe_unregister(&__tracepoint_##name,\