gistfile1.txt

(gdb) info threads
  6 Thread 0x40b93940 (LWP 15361)  0x00000037efa0aee9 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
  5 Thread 0x42755940 (LWP 15431)  0x00000037efa0cd01 in sem_wait () from /lib64/libpthread.so.0
  4 Thread 0x413b7940 (LWP 15771)  0x00000037efa0aee9 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
  3 Thread 0x41c0d940 (LWP 15772)  0x00000037efa0aee9 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
  2 Thread 0x4011d940 (LWP 19424)  0x00000037eeacd722 in select () from /lib64/libc.so.6
* 1 Thread 0x2b96ec0facc0 (LWP 15167)  0x00000037eeabb187 in sched_yield () from /lib64/libc.so.6
(gdb) bt full
#0  0x00000037eeabb187 in sched_yield () from /lib64/libc.so.6
No symbol table info available.
#1  0x00002b96ebe39ba3 in gvl_yield (vm=0x55f8f20, th=<value optimized out>) at thread_pthread.c:123
No locals.
#2  0x00002b96ebe39f39 in rb_thread_schedule_limits () at thread.c:1025
No locals.
#3  rb_thread_schedule () at thread.c:1035
No locals.
#4  0x00002b96ebe3a136 in rb_thread_terminate_all () at thread.c:375
        _th = 0x55f9520
        _tag = {buf = {{__jmpbuf = {0, 7509665241996969646, 0, 140736260182128, 0, 90150176, 7509698779018709598, 7509641504071116675}, __mask_was_saved = 0, __saved_mask = {__val = {140736260182128, 0, 0, 7509698779018709902,
                  7509641504068102843, 140733193388032, 240243474669, 0, 47927202636682, 0, 8, 0, 140736260186112, 10485760, 301905312, 32}}}}, tag = 0, retval = 91278704, prev = 0x7fffb6cb8e50}
        th = <value optimized out>
        vm = 0x55f8f20
#5  0x00002b96ebd1af8e in ruby_cleanup (ex=6) at eval.c:140
        _th = 0x55f9520
        _tag = {buf = {{__jmpbuf = {90150176, 7509665241996969646, 0, 140736260182128, 0, 0, 7509698779018709134, 7509641504068103008}, __mask_was_saved = 0, __saved_mask = {__val = {140736260182128, 0, 0, 47927201075200, 240222523141,
                  5, 0, 10485760, 100700896, 47927201105296, 96114960, 0, 240222546306, 6, 0, 90150176}}}}, tag = 0, retval = 6, prev = 0x0}
        state = <value optimized out>
        errs = {161115400, 161115400}
        th = 0x55f9520
#6  0x00002b96ebd1b0d6 in ruby_run_node (n=0x5ba9910) at eval.c:244
        status = <value optimized out>
#7  0x00000000004008bf in main (argc=8, argv=0x7fffb6cb9078) at main.c:38
        variable_in_this_stack_frame = 240224684992

step-through

(gdb)
372         while (!rb_thread_alone()) {
(gdb) list
367
368         thread_debug("rb_thread_terminate_all (main thread: %p)\n", (void *)th);
369         st_foreach(vm->living_threads, terminate_i, (st_data_t)th);
370         vm->inhibit_thread_creation = 1;
371
372         while (!rb_thread_alone()) {
373             PUSH_TAG();
374             if (EXEC_TAG() == 0) {
375                 rb_thread_schedule();
376             }
(gdb) step
rb_thread_alone () at thread.c:2171
2171        if (GET_THREAD()->vm->living_threads) {
(gdb) list
2166
2167    int
2168    rb_thread_alone(void)
2169    {
2170        int num = 1;
2171        if (GET_THREAD()->vm->living_threads) {
2172            num = vm_living_thread_num(GET_THREAD()->vm);
2173            thread_debug("rb_thread_alone: %d\n", num);
2174        }
2175        return num == 1;
(gdb) p num
$1 = <value optimized out>
(gdb) stepi
0x00002b96ebe354f7      2171        if (GET_THREAD()->vm->living_threads) {
(gdb)
0x00002b96ebe354fa      2171        if (GET_THREAD()->vm->living_threads) {
(gdb)
0x00002b96ebe354fe      2171        if (GET_THREAD()->vm->living_threads) {
(gdb)
0x00002b96ebe35505      2171        if (GET_THREAD()->vm->living_threads) {
(gdb)
0x00002b96ebe3550a      2171        if (GET_THREAD()->vm->living_threads) {
(gdb)
0x00002b96ebe3550d      2171        if (GET_THREAD()->vm->living_threads) {
(gdb)
0x00002b96ebe3550f      2171        if (GET_THREAD()->vm->living_threads) {
(gdb)
0x00002b96ebe35513      2171        if (GET_THREAD()->vm->living_threads) {
(gdb)
0x00002b96ebe35516      2171        if (GET_THREAD()->vm->living_threads) {
(gdb)
0x00002b96ebe35519      2171        if (GET_THREAD()->vm->living_threads) {
(gdb)
0x00002b96ebe3551c      2171        if (GET_THREAD()->vm->living_threads) {
(gdb)
2176    }
(gdb) p num
$2 = <value optimized out>
(gdb) p num == 1
$3 = 0

strace

sched_yield()                           = 0
sched_yield()                           = 0
sched_yield()                           = 0
sched_yield()                           = 0
sched_yield()                           = 0
sched_yield()                           = 0
sched_yield()                           = 0
sched_yield()                           = 0
sched_yield()                           = 0
sched_yield()                           = 0
sched_yield()                           = 0
sched_yield()                           = 0
sched_yield()                           = 0
sched_yield()                           = 0
sched_yield()                           = 0
(and so on)