Hi! Thanks for reaching out.
Which version of cuda-gdb are you using? This will help us diagnose the issue.
Also, could you try the following instead to see if it performs better:
(cuda-gdb) break Reductions.cuh:42
(cuda-gdb) continue
The s or step command is typically used in the following way:
(cuda-gdb) help s
step, s
Step program until it reaches a different source line.
Usage: step [N]
Argument N means step N times (or till program stops for another reason).