Maybe the USR1 signal is from the test runner that kills the process after it has been stuck for a long time.
I observed the first tests run quickly but then it grinds to a halt. But it could just be because of hitting the bug that traps stops/crashes server without returning control. I didn't install all symbols as I don't have the skills to read the full code path / stack trace and write a patch for sparc64 compatibility myself. I am not debugging this further right now, need to debug upgrade issues that affects all platforms.
