On 3/26/18 9:17 AM, Mathieu Desnoyers wrote:

quoted

re: 'added complexity'...
-       for (iter = begin; iter < end; iter++)
-               fct(*iter, priv);
+               return NULL;
+       for (iter = begin; iter < end; iter++) {
+               ret = fct(*iter, priv);
+               if (ret)
+                       return ret;
+       }
+       return NULL;

where do you see 'added complexity' ?
Isn't the above diff self-explanatory that for_each_tracepoint_range()
can be used not only to iterate over all tracepoints
(just do 'return NULL') from callback _and_ to find one particular
tracepoint as patch 7 does ?

I am not arguing about your proposed implementation. I am arguing about
the lack of justification behind this change. Why is this change needed ?
What is it allowing you to do that cannot be done using the private data
pointer ?

commit log of patch 6 states:

"for_each_tracepoint_range() api has no users inside the kernel.
Make it more useful with ability to stop for_each() loop depending
via callback return value.
In such form it's used in subsequent patch."

and in patch 7:

+static void *__find_tp(struct tracepoint *tp, void *priv)
+{
+       char *name = priv;
+
+       if (!strcmp(tp->name, name))
+               return tp;
+       return NULL;
+}
...
+       struct tracepoint *tp;
...
+       tp = for_each_kernel_tracepoint(__find_tp, tp_name);
+       if (!tp)
+               return -ENOENT;

still not obvious?