valgrind: the 'impossible' happened:
   VG_N_THREADS is too low
==6011==    at 0x70010E08: report_and_quit (m_libcassert.c:122)
==6011==    by 0x700110F0: panic (m_libcassert.c:195)
==6011==    by 0x70011113: vgPlain_core_panic_at (m_libcassert.c:200)
==6011==    by 0x70011131: vgPlain_core_panic (m_libcassert.c:205)
==6011==    by 0x7003369E: vgPlain_alloc_ThreadState (scheduler.c:180)
==6011==    by 0x7005281F: do_clone (syswrap-amd64-linux.c:203)
==6011==    by 0x70052CF6: vgSysWrap_amd64_linux_sys_clone_before (syswrap-amd64-linux.c:406)
==6011==    by 0x7004634E: vgPlain_client_syscall (syswrap-main.c:658)
==6011==    by 0x70034597: handle_syscall (scheduler.c:623)
==6011==    by 0x700348AC: vgPlain_scheduler (scheduler.c:726)
==6011==    by 0x700477CE: thread_wrapper (syswrap-linux.c:87)
==6011==    by 0x700478C5: run_a_thread_NORETURN (syswrap-linux.c:120)
==6011==    by 0x700479F6: vgModuleLocal_start_thread_NORETURN (syswrap-linux.c:207)
==6011==    by 0x700527CE: (within /usr/lib64/valgrind/amd64-linux/memcheck)