On 08/22/2013 04:49:31 PM, Zoltan Kiss wrote:
The sample missed the moving of the header files into the events
subdirectory.
I've also extended it based on the existing headers, and mentioned
the tiny
but important role of CREATE_TRACE_POINTS.
Signed-off-by: Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>
---
Documentation/trace/tracepoints.txt | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)
diff --git a/Documentation/trace/tracepoints.txt
b/Documentation/trace/tracepoints.txt
index da49437..e8e3c4b 100644
--- a/Documentation/trace/tracepoints.txt
+++ b/Documentation/trace/tracepoints.txt
@@ -40,7 +40,13 @@ Two elements are required for tracepoints :
In order to use tracepoints, you should include linux/tracepoint.h.
-In include/trace/subsys.h :
+In include/trace/events/subsys.h :
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM subsys
That addition I can sort of see, I guess?
+#if !defined(_TRACE_SUBSYS_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_SUBSYS_H
But this makes no sense to me: why is it needed? (I.E. why must it be
block copied into each _user_ of tracepoints?)
#include <linux/tracepoint.h>
@@ -48,10 +54,16 @@ DECLARE_TRACE(subsys_eventname,
TP_PROTO(int firstarg, struct task_struct *p),
TP_ARGS(firstarg, p));
+#endif /* _TRACE_SUBSYS_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
+
Why? (Both why do you need to #include a header outside a multiple
inclusion guard, and why is the additional header needed at all in
_every_ subsystem trace header?)
In subsys/file.c (where the tracing statement must be added) :
-#include <trace/subsys.h>
+#include <trace/events/subsys.h>
+#define CREATE_TRACE_POINTS
DEFINE_TRACE(subsys_eventname);
void somefct(void)
@@ -72,6 +84,9 @@ Where :
- TP_ARGS(firstarg, p) are the parameters names, same as found in the
prototype.
+- if you use the header in multiple source files, #define
CREATE_TRACE_POINTS
+ should appear only in one source file
+
Connecting a function (probe) to a tracepoint is done by providing a
probe (function to call) for the specific tracepoint through
register_trace_subsys_eventname(). Removing a probe is done through
I guess the documentation isn't at fault if the tracepoint subsystem is
suddenly becoming a lot more repetitive and complicated for no readily
apparent reason, but did anybody ask _why_ this thing changed? Can we
document why the extra redundancy is needed?
Rob--
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