perf callchain: Introduce callchain_cursor__copy()

The callchain_cursor__copy() function is to save current callchain
captured by a cursor.  It'll be used to keep callchains when switching
to idle task for each cpu.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20161206034010.6499-3-namhyung@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/callchain.c

@@ -1234,3 +1234,30 @@ int callchain_node__make_parent_list(struct callchain_node *node)
 	}
 	return -ENOMEM;
 }
+
+int callchain_cursor__copy(struct callchain_cursor *dst,
+			   struct callchain_cursor *src)
+{
+	int rc = 0;
+
+	callchain_cursor_reset(dst);
+	callchain_cursor_commit(src);
+
+	while (true) {
+		struct callchain_cursor_node *node;
+
+		node = callchain_cursor_current(src);
+		if (node == NULL)
+			break;
+
+		rc = callchain_cursor_append(dst, node->ip, node->map, node->sym,
+					     node->branch, &node->branch_flags,
+					     node->nr_loop_iter, node->samples);
+		if (rc)
+			break;
+
+		callchain_cursor_advance(src);
+	}
+
+	return rc;
+}

tools/perf/util/callchain.h

@@ -216,6 +216,9 @@ static inline void callchain_cursor_advance(struct callchain_cursor *cursor)
 	cursor->pos++;
 }
 
+int callchain_cursor__copy(struct callchain_cursor *dst,
+			   struct callchain_cursor *src);
+
 struct option;
 struct hist_entry;