Hi Miloody

I found there seems no declaring about "struct ftrace_entry".
below the greping result of my kernel source code:

# grep -rwn 'struct ftrace_entry' *
kernel/trace/trace.h:214: ? ? ? ? ? ? ? IF_ASSIGN(var, ent, struct ftrace_entry, TRACE_FN); ? ? \
kernel/trace/trace_events.c:1483: ? ? ? struct ftrace_entry *entry;
kernel/trace/trace_output.c:818: ? ? ? ?struct ftrace_entry *field;
kernel/trace/trace_output.c:845: ? ? ? ?struct ftrace_entry *field;
kernel/trace/trace_output.c:859: ? ? ? ?struct ftrace_entry *field;
kernel/trace/trace_output.c:872: ? ? ? ?struct ftrace_entry *field;
kernel/trace/trace.c:1098: ? ? ?struct ftrace_entry *entry;

usually we use a struct we will declare its elements such as:

struct usb_host_endpoint {
? ? ? ?struct usb_endpoint_descriptor ?desc;
? ? ? ?struct list_head ? ? ? ? ? ? ? ?urb_list;
? ? ? ?void ? ? ? ? ? ? ? ? ? ? ? ? ? ?*hcpriv;
......................
};

I think this struct is not explicitly declared but generated by a macro. Look in

kernel/trace/trace_entries.h

The code that uses struct ftrace_entry all seems to #include this file
either directly or indirectly:

Directly by kernel/trace/trace_export.c and kernel/trace/trace.h

Then kernel/trace/trace.c includes trace.h
kernel/trace/trace_output.h includes trace.h
kernel/trace/trace_output.c and kernel/trace/trace_events.c include
trace_output.h

I don't know why there is an advantage to creating a struct this way
(perhaps a performance/storage advantage?) but then I haven't looked
at the code in a lot of detail.

Cheers
Julie