How to debug cuda program with multiple threads?

My question seems a continuation to this one. I want to debug a app that uses cuda. When I start it in gdb I get 7 threads created before I hit the main(), same as in the linked question. But then when I step over I keep repeating the same lines multiple times, like if each thread was running an app and I was jumping from one thread to another. See execution:

$ gdb ./ElasticFusion 
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Reading symbols from ./ElasticFusion...done.
(gdb) start
Temporary breakpoint 1 at 0x418540: file /home/martin/develop/thirdparty/drl_elasticfusionpublic/GUI/src/Main.cpp, line 22.
Starting program: /home/martin/develop/thirdparty/drl_elasticfusionpublic/GUI/build/ElasticFusion 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7fffe078c700 (LWP 3527)]
[New Thread 0x7fffdff8b700 (LWP 3528)]
[New Thread 0x7fffdd78a700 (LWP 3529)]
[New Thread 0x7fffdaf89700 (LWP 3530)]
[New Thread 0x7fffd6788700 (LWP 3531)]
[New Thread 0x7fffd3f87700 (LWP 3532)]
[New Thread 0x7fffd1786700 (LWP 3533)]

Thread 1 "ElasticFusion" hit Temporary breakpoint 1, main (argc=1, argv=0x7fffffffdbb8)
    at /home/martin/develop/thirdparty/drl_elasticfusionpublic/GUI/src/Main.cpp:22
22  {
(gdb) n
23      MainController mainController(argc, argv);
(gdb) n
22  {
(gdb) n
23      MainController mainController(argc, argv);
(gdb) n
22  {
(gdb) n
23      MainController mainController(argc, argv);
(gdb) n
Creating live capture... [New Thread 0x7fffce85c700 (LWP 3535)]

Why do I get the same line repeated? is the main() being executed in multiple threads?? the app hasn't spawned any threads yet that I can see. How do I debug this?