(gdb) info threads
  Id   Target Id         Frame 
* 1    Thread 0x7f79872e8740 (LWP 15176) "ruby" 0x00007f7985f8c1d7 in sched_yield () at ../sysdeps/unix/syscall-template.S:81
(gdb) 


(gdb) backtrace
#0  0x00007f7985f8c1d7 in sched_yield () at ../sysdeps/unix/syscall-template.S:81
#1  0x00007f7986fa86f5 in native_stop_timer_thread () at thread_pthread.c:1664
#2  rb_thread_stop_timer_thread () at thread.c:3929
#3  0x00007f7986eaf3e6 in before_exec_non_async_signal_safe () at process.c:1175
#4  before_exec () at process.c:1181
#5  rb_f_exec (argc=<optimised out>, argv=<optimised out>) at process.c:2576
#6  0x00007f7986f7c706 in vm_call_cfunc_with_frame (ci=<optimised out>, cc=<optimised out>, calling=<optimised out>, reg_cfp=0x7f79872e6210, th=0x7f7988f255d0) at vm_insnhelper.c:1642
#7  vm_call_cfunc (th=0x7f7988f255d0, reg_cfp=0x7f79872e6210, calling=<optimised out>, ci=<optimised out>, cc=<optimised out>) at vm_insnhelper.c:1737
#8  0x00007f7986f8a683 in vm_call_method (th=0x7f7988f255d0, cfp=0x7f79872e6210, calling=<optimised out>, ci=<optimised out>, cc=<optimised out>) at vm_insnhelper.c:2176
#9  0x00007f7986f84f69 in vm_exec_core (th=th@entry=0x7f7988f255d0, initial=initial@entry=0) at insns.def:994
#10 0x00007f7986f88cd1 in vm_exec (th=0x7f7988f255d0) at vm.c:1650
#11 0x00007f7986f89473 in invoke_block (th=th@entry=0x7f7988f255d0, iseq=iseq@entry=0x7f7989d16640, self=self@entry=140159979832400, cref=cref@entry=0x0, type=<optimised out>, opt_pc=0, 
    block=0x7f798ba29a90) at vm.c:921
#12 0x00007f7986f8981e in invoke_block_from_c_0 (th=0x7f7988f255d0, block=0x7f798ba29a90, self=140159979832400, argc=<optimised out>, argv=<optimised out>, blockptr=<optimised out>, cref=0x0, 
    splattable=0) at vm.c:971
#13 0x00007f7986f898f8 in invoke_block_from_c_unsplattable (cref=0x0, blockptr=0x0, argv=0x7fffe6a81730, argc=1, self=140159979832400, block=0x7f798ba29a90, th=0x7f7988f255d0) at vm.c:996
#14 vm_invoke_proc (th=th@entry=0x7f7988f255d0, proc=proc@entry=0x7f798ba29a90, self=140159979832400, argc=argc@entry=1, argv=0x7fffe6a81730, blockptr=0x0) at vm.c:1044
#15 0x00007f7986f8a0b7 in rb_vm_invoke_proc (blockptr=<optimised out>, argv=<optimised out>, argc=1, proc=0x7f798ba29a90, th=0x7f7988f255d0) at vm.c:1072
#16 vm_call_opt_call (th=0x7f7988f255d0, cfp=0x7f79872e6250, calling=0x7fffe6a818c0, ci=<optimised out>, cc=<optimised out>) at vm_insnhelper.c:1868
#17 0x00007f7986f8a683 in vm_call_method (th=0x7f7988f255d0, cfp=0x7f79872e6250, calling=<optimised out>, ci=<optimised out>, cc=<optimised out>) at vm_insnhelper.c:2176
#18 0x00007f7986f84f69 in vm_exec_core (th=th@entry=0x7f7988f255d0, initial=initial@entry=0) at insns.def:994
#19 0x00007f7986f88cd1 in vm_exec (th=0x7f7988f255d0) at vm.c:1650
#20 0x00007f7986f89473 in invoke_block (th=th@entry=0x7f7988f255d0, iseq=iseq@entry=0x7f7989d15b78, self=self@entry=140159979832400, cref=cref@entry=0x0, type=<optimised out>, opt_pc=0, 
    block=<optimised out>) at vm.c:921
#21 0x00007f7986f8b361 in invoke_block_from_c_0 (argc=<optimised out>, blockptr=<optimised out>, cref=<optimised out>, splattable=<optimised out>, argv=<optimised out>, self=<optimised out>, 
    block=<optimised out>, th=<optimised out>) at vm.c:971
#22 invoke_block_from_c_splattable (cref=<optimised out>, blockptr=<optimised out>, argv=<optimised out>, argc=<optimised out>, self=<optimised out>, block=<optimised out>, th=<optimised out>)
    at vm.c:988
#23 vm_yield (argc=<optimised out>, argv=<optimised out>, th=<optimised out>) at vm.c:1023
#24 rb_yield_0 (argv=<optimised out>, argc=<optimised out>) at vm_eval.c:1013
#25 rb_yield_1 (val=<optimised out>) at vm_eval.c:1019
#26 rb_yield (val=val@entry=52) at vm_eval.c:1029
#27 0x00007f7986e35431 in rb_protect (proc=0x7f7986f8b0c0 <rb_yield>, data=data@entry=52, state=state@entry=0x7fffe6a8208c) at eval.c:894
#28 0x00007f7986ea7189 in rb_f_fork (obj=<optimised out>) at process.c:3721
#29 0x00007f7986f7c706 in vm_call_cfunc_with_frame (ci=<optimised out>, cc=<optimised out>, calling=<optimised out>, reg_cfp=0x7f79872e62d0, th=0x7f7988f255d0) at vm_insnhelper.c:1642
#30 vm_call_cfunc (th=0x7f7988f255d0, reg_cfp=0x7f79872e62d0, calling=<optimised out>, ci=<optimised out>, cc=<optimised out>) at vm_insnhelper.c:1737
#31 0x00007f7986f84e9e in vm_exec_core (th=th@entry=0x7f7988f255d0, initial=initial@entry=0) at insns.def:963
#32 0x00007f7986f88cd1 in vm_exec (th=0x7f7988f255d0) at vm.c:1650
#33 0x00007f7986f89473 in invoke_block (th=th@entry=0x7f7988f255d0, iseq=iseq@entry=0x7f798a6840d8, self=self@entry=140159989854240, cref=cref@entry=0x0, type=<optimised out>, opt_pc=0, 
    block=<optimised out>) at vm.c:921
#34 0x00007f7986f8b719 in invoke_block_from_c_0 (argc=1, blockptr=0x0, cref=0x0, splattable=1, argv=0x7fffe6a82688, self=140159989854240, block=0x7f79872e6470, th=0x7f7988f255d0) at vm.c:971
#35 invoke_block_from_c_splattable (cref=0x0, blockptr=0x0, argv=0x7fffe6a82688, argc=1, self=140159989854240, block=<optimised out>, th=0x7f7988f255d0) at vm.c:988
#36 vm_yield (argc=1, argv=0x7fffe6a82688, th=0x7f7988f255d0) at vm.c:1023
#37 rb_yield_0 (argv=0x7fffe6a82688, argc=1) at vm_eval.c:1013
#38 catch_i (tag=<optimised out>, data=data@entry=0) at vm_eval.c:1921
#39 0x00007f7986f7ef5e in rb_catch_protect (t=<optimised out>, func=func@entry=0x7f7986f8b580 <catch_i>, data=data@entry=0, stateptr=stateptr@entry=0x7fffe6a82860) at vm_eval.c:2021
#40 0x00007f7986f7f0e1 in rb_catch_obj (data=0, func=0x7f7986f8b580 <catch_i>, t=<optimised out>) at vm_eval.c:2000
#41 rb_f_catch (argc=<optimised out>, argv=<optimised out>) at vm_eval.c:1986
#42 0x00007f7986f7c706 in vm_call_cfunc_with_frame (ci=<optimised out>, cc=<optimised out>, calling=<optimised out>, reg_cfp=0x7f79872e6450, th=0x7f7988f255d0) at vm_insnhelper.c:1642
#43 vm_call_cfunc (th=0x7f7988f255d0, reg_cfp=0x7f79872e6450, calling=<optimised out>, ci=<optimised out>, cc=<optimised out>) at vm_insnhelper.c:1737
#44 0x00007f7986f84e9e in vm_exec_core (th=th@entry=0x7f7988f255d0, initial=initial@entry=0) at insns.def:963
#45 0x00007f7986f88cd1 in vm_exec (th=0x7f7988f255d0) at vm.c:1650
#46 0x00007f7986f89473 in invoke_block (th=th@entry=0x7f7988f255d0, iseq=iseq@entry=0x7f798e7dd908, self=self@entry=140160011042640, cref=cref@entry=0x0, type=<optimised out>, opt_pc=0, 
    block=<optimised out>) at vm.c:921
#47 0x00007f7986f8b361 in invoke_block_from_c_0 (argc=<optimised out>, blockptr=<optimised out>, cref=<optimised out>, splattable=<optimised out>, argv=<optimised out>, self=<optimised out>, 
    block=<optimised out>, th=<optimised out>) at vm.c:971
#48 invoke_block_from_c_splattable (cref=<optimised out>, blockptr=<optimised out>, argv=<optimised out>, argc=<optimised out>, self=<optimised out>, block=<optimised out>, th=<optimised out>)
    at vm.c:988
#49 vm_yield (argc=<optimised out>, argv=<optimised out>, th=<optimised out>) at vm.c:1023
#50 rb_yield_0 (argv=<optimised out>, argc=<optimised out>) at vm_eval.c:1013
#51 rb_yield_1 (val=<optimised out>) at vm_eval.c:1019
#52 rb_yield (val=<optimised out>) at vm_eval.c:1029
#53 0x00007f7986fafddd in rb_ary_each (ary=140160055439080) at array.c:1815
#54 0x00007f7986f7c706 in vm_call_cfunc_with_frame (ci=<optimised out>, cc=<optimised out>, calling=<optimised out>, reg_cfp=0x7f79872e6910, th=0x7f7988f255d0) at vm_insnhelper.c:1642
#55 vm_call_cfunc (th=0x7f7988f255d0, reg_cfp=0x7f79872e6910, calling=<optimised out>, ci=<optimised out>, cc=<optimised out>) at vm_insnhelper.c:1737
#56 0x00007f7986f8a683 in vm_call_method (th=0x7f7988f255d0, cfp=0x7f79872e6910, calling=<optimised out>, ci=<optimised out>, cc=<optimised out>) at vm_insnhelper.c:2176
---Type <return> to continue, or q <return> to quit---
#57 0x00007f7986f84e9e in vm_exec_core (th=th@entry=0x7f7988f255d0, initial=initial@entry=0) at insns.def:963
#58 0x00007f7986f88cd1 in vm_exec (th=0x7f7988f255d0) at vm.c:1650
#59 0x00007f7986f89473 in invoke_block (th=th@entry=0x7f7988f255d0, iseq=iseq@entry=0x7f798e7df6e0, self=self@entry=140160011042640, cref=cref@entry=0x0, type=<optimised out>, opt_pc=0, 
    block=<optimised out>) at vm.c:921
#60 0x00007f7986f8b361 in invoke_block_from_c_0 (argc=<optimised out>, blockptr=<optimised out>, cref=<optimised out>, splattable=<optimised out>, argv=<optimised out>, self=<optimised out>, 
    block=<optimised out>, th=<optimised out>) at vm.c:971
#61 invoke_block_from_c_splattable (cref=<optimised out>, blockptr=<optimised out>, argv=<optimised out>, argc=<optimised out>, self=<optimised out>, block=<optimised out>, th=<optimised out>)
    at vm.c:988
#62 vm_yield (argc=<optimised out>, argv=<optimised out>, th=<optimised out>) at vm.c:1023
#63 rb_yield_0 (argv=<optimised out>, argc=<optimised out>) at vm_eval.c:1013
#64 rb_yield_1 (val=<optimised out>) at vm_eval.c:1019
#65 rb_yield (val=<optimised out>) at vm_eval.c:1029
#66 0x00007f7986fafddd in rb_ary_each (ary=140160054897840) at array.c:1815
#67 0x00007f7986f7c706 in vm_call_cfunc_with_frame (ci=<optimised out>, cc=<optimised out>, calling=<optimised out>, reg_cfp=0x7f79872e6b10, th=0x7f7988f255d0) at vm_insnhelper.c:1642
#68 vm_call_cfunc (th=0x7f7988f255d0, reg_cfp=0x7f79872e6b10, calling=<optimised out>, ci=<optimised out>, cc=<optimised out>) at vm_insnhelper.c:1737
#69 0x00007f7986f84e9e in vm_exec_core (th=th@entry=0x7f7988f255d0, initial=initial@entry=0) at insns.def:963
#70 0x00007f7986f88cd1 in vm_exec (th=0x7f7988f255d0) at vm.c:1650
#71 0x00007f7986f89473 in invoke_block (th=th@entry=0x7f7988f255d0, iseq=iseq@entry=0x7f798a6839d0, self=self@entry=140159989854320, cref=cref@entry=0x0, type=<optimised out>, opt_pc=0, 
    block=0x7f798f3a4180) at vm.c:921
#72 0x00007f7986f8981e in invoke_block_from_c_0 (th=0x7f7988f255d0, block=0x7f798f3a4180, self=140159989854320, argc=<optimised out>, argv=<optimised out>, blockptr=<optimised out>, cref=0x0, 
    splattable=0) at vm.c:971
#73 0x00007f7986f898f8 in invoke_block_from_c_unsplattable (cref=0x0, blockptr=0x0, argv=0x7fffe6a83e10, argc=1, self=140159989854320, block=0x7f798f3a4180, th=0x7f7988f255d0) at vm.c:996
#74 vm_invoke_proc (th=th@entry=0x7f7988f255d0, proc=proc@entry=0x7f798f3a4180, self=140159989854320, argc=argc@entry=1, argv=0x7fffe6a83e10, blockptr=0x0) at vm.c:1044
#75 0x00007f7986f8a0b7 in rb_vm_invoke_proc (blockptr=<optimised out>, argv=<optimised out>, argc=1, proc=0x7f798f3a4180, th=0x7f7988f255d0) at vm.c:1072
#76 vm_call_opt_call (th=0x7f7988f255d0, cfp=0x7f79872e6c90, calling=0x7fffe6a83fa0, ci=<optimised out>, cc=<optimised out>) at vm_insnhelper.c:1868
#77 0x00007f7986f8a683 in vm_call_method (th=0x7f7988f255d0, cfp=0x7f79872e6c90, calling=<optimised out>, ci=<optimised out>, cc=<optimised out>) at vm_insnhelper.c:2176
#78 0x00007f7986f84f69 in vm_exec_core (th=th@entry=0x7f7988f255d0, initial=initial@entry=0) at insns.def:994
#79 0x00007f7986f88cd1 in vm_exec (th=0x7f7988f255d0) at vm.c:1650
#80 0x00007f7986f89473 in invoke_block (th=th@entry=0x7f7988f255d0, iseq=iseq@entry=0x7f798a555e78, self=self@entry=140159988614720, cref=cref@entry=0x0, type=<optimised out>, opt_pc=0, 
    block=<optimised out>) at vm.c:921
#81 0x00007f7986f8b361 in invoke_block_from_c_0 (argc=<optimised out>, blockptr=<optimised out>, cref=<optimised out>, splattable=<optimised out>, argv=<optimised out>, self=<optimised out>, 
    block=<optimised out>, th=<optimised out>) at vm.c:971
#82 invoke_block_from_c_splattable (cref=<optimised out>, blockptr=<optimised out>, argv=<optimised out>, argc=<optimised out>, self=<optimised out>, block=<optimised out>, th=<optimised out>)
    at vm.c:988
#83 vm_yield (argc=<optimised out>, argv=<optimised out>, th=<optimised out>) at vm.c:1023
#84 rb_yield_0 (argv=<optimised out>, argc=<optimised out>) at vm_eval.c:1013
#85 rb_yield_1 (val=<optimised out>) at vm_eval.c:1019
#86 rb_yield (val=<optimised out>) at vm_eval.c:1029
#87 0x00007f7986fafddd in rb_ary_each (ary=140160040180840) at array.c:1815
#88 0x00007f7986f7c706 in vm_call_cfunc_with_frame (ci=<optimised out>, cc=<optimised out>, calling=<optimised out>, reg_cfp=0x7f79872e6e90, th=0x7f7988f255d0) at vm_insnhelper.c:1642
#89 vm_call_cfunc (th=0x7f7988f255d0, reg_cfp=0x7f79872e6e90, calling=<optimised out>, ci=<optimised out>, cc=<optimised out>) at vm_insnhelper.c:1737
#90 0x00007f7986f84e9e in vm_exec_core (th=th@entry=0x7f7988f255d0, initial=initial@entry=0) at insns.def:963
#91 0x00007f7986f88cd1 in vm_exec (th=0x7f7988f255d0) at vm.c:1650
#92 0x00007f7986f89473 in invoke_block (th=th@entry=0x7f7988f255d0, iseq=iseq@entry=0x7f798aac4800, self=self@entry=140160012382840, cref=cref@entry=0x0, type=<optimised out>, opt_pc=0, 
    block=<optimised out>) at vm.c:921
#93 0x00007f7986f8b8b1 in invoke_block_from_c_0 (argc=0, argv=0x0, blockptr=0x0, cref=0x0, splattable=1, self=140160012382840, block=0x7f79872e6f70, th=0x7f7988f255d0) at vm.c:971
#94 invoke_block_from_c_splattable (cref=0x0, blockptr=0x0, argv=0x0, argc=0, self=140160012382840, block=<optimised out>, th=0x7f7988f255d0) at vm.c:988
#95 vm_yield (argc=0, argv=0x0, th=0x7f7988f255d0) at vm.c:1023
#96 rb_yield_0 (argv=0x0, argc=0) at vm_eval.c:1013
#97 loop_i () at vm_eval.c:1090
#98 0x00007f7986e35172 in rb_rescue2 (b_proc=0x7f7986f8b740 <loop_i>, data1=0, r_proc=0x7f7986f77d00 <loop_stop>, data2=0) at eval.c:826
#99 0x00007f7986f7c706 in vm_call_cfunc_with_frame (ci=<optimised out>, cc=<optimised out>, calling=<optimised out>, reg_cfp=0x7f79872e6f50, th=0x7f7988f255d0) at vm_insnhelper.c:1642
#100 vm_call_cfunc (th=0x7f7988f255d0, reg_cfp=0x7f79872e6f50, calling=<optimised out>, ci=<optimised out>, cc=<optimised out>) at vm_insnhelper.c:1737
#101 0x00007f7986f8a683 in vm_call_method (th=0x7f7988f255d0, cfp=0x7f79872e6f50, calling=<optimised out>, ci=<optimised out>, cc=<optimised out>) at vm_insnhelper.c:2176
#102 0x00007f7986f84e9e in vm_exec_core (th=th@entry=0x7f7988f255d0, initial=initial@entry=0) at insns.def:963
#103 0x00007f7986f88cd1 in vm_exec (th=0x7f7988f255d0) at vm.c:1650
#104 0x00007f7986f92cee in rb_iseq_eval_main (iseq=iseq@entry=0x7f7989178ba8) at vm.c:1893
#105 0x00007f7986e30c24 in ruby_exec_internal (n=0x7f7989178ba8) at eval.c:245
#106 0x00007f7986e346ed in ruby_exec_node (n=0x7f7989178ba8) at eval.c:310
#107 ruby_run_node (n=<optimised out>) at eval.c:302
#108 0x00007f7986e3088b in main (argc=2, argv=0x7fffe6a85638) at main.c:36