Initialize Mutex's at the start of Init process

[eightbitraptor]

Running GC requres these Mutex's to be initialised but the code that
initialises them (in thread.c) happens after the initialisation of the
GC.

Normally this wouldn't be a problem because GC wouldn't need to run
during the Ruby initialisation process.

Since we've added Garbage to the end of an RVALUE, we now reach the end
of a transient heap page during the startup process which triggers a GC
run - which crashes because the mutex's aren't initialised so the OS
rejects the request for the lock.

This patch extracts the mutex initialisation from Init_Thread and pulls
it right to the top of the ruby initialisation process so they're going
to be usable no matter when the GC runs.

Initially we tried to workaround this by just moving the ordering of the
initialisations in inits.c. This turned into a game of whack a mole as
there are dependencies between a lot of these items.

We chose this approach as it makes it clearer exactly which code that we
are depending on and that it needs to run first in the initialisation
queue.

Logs

Here is the output of make runruby

mattvh@tomoe ~/s/r/build [1]> make runruby
compiling ../ruby/eval.c
compiling ../ruby/gc.c
../ruby/gc.c:2190:1: warning: control reaches end of non-void function [-Wreturn-type]
}
^
../ruby/gc.c:4237:1: warning: control reaches end of non-void function [-Wreturn-type]
}
^
2 warnings generated.
../ruby/revision.h updated
compiling ../ruby/version.c
generating vm_call_iseq_optimized.inc
vm_call_iseq_optimized.inc unchanged
linking miniruby
[BUG] pthread_mutex_lock: Invalid argument (EINVAL)
ruby 2.8.0dev (2020-06-29T19:53:08Z allocate-garbage 9fcdabf3a3) [x86_64-darwin19]

-- Crash Report log information --------------------------------------------
   See Crash Report log file under the one of following:
     * ~/Library/Logs/DiagnosticReports
     * /Library/Logs/DiagnosticReports
   for more details.
Don't forget to include the above Crash Report log file in bug reports.

-- Control frame information -----------------------------------------------
c:0002 p:---- s:0006 e:000005 CFUNC  :inherited
c:0001 p:---- s:0003 e:000002 (none) [FINISH]

[BUG] Segmentation fault at 0x0000000000000000
ruby 2.8.0dev (2020-06-29T19:53:08Z allocate-garbage 9fcdabf3a3) [x86_64-darwin19]

-- Crash Report log information --------------------------------------------
   See Crash Report log file under the one of following:
     * ~/Library/Logs/DiagnosticReports
     * /Library/Logs/DiagnosticReports
   for more details.
Don't forget to include the above Crash Report log file in bug reports.

-- Control frame information -----------------------------------------------
c:0002 p:---- s:0006 e:000005 CFUNC  :inherited
c:0001 p:---- s:0003 e:000002 (none) [FINISH]

here is the stacktrace as captured by lldb

(lldb) thread backtrace
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
  * frame #0: 0x0000000100323c90 miniruby`RB_FL_TEST_RAW(obj=0, flags=8192) at fl_type.h:235:25
    frame #1: 0x0000000100323c2d miniruby`RB_FL_ANY_RAW(obj=0, flags=8192) at fl_type.h:256:12
    frame #2: 0x00000001003242b8 miniruby`rbimpl_rstring_getmem(str=0) at rstring.h:127:9
    frame #3: 0x00000001003228f7 miniruby`RSTRING_PTR(str=0) at rstring.h:153:17
    frame #4: 0x00000001003206b6 miniruby`oldbt_bugreport(arg=0x00007ffeefbfdef4, file=0, line=0, method=4321210992) at vm_backtrace.c:826:51
    frame #5: 0x00000001003208cb miniruby`oldbt_iter_cfunc(ptr=0x00007ffeefbfdef8, cfp=0x0000000101319f90, mid=3969) at vm_backtrace.c:791:5
    frame #6: 0x00000001003200cb miniruby`backtrace_each(ec=0x0000000101107210, init=(miniruby`oldbt_init at vm_backtrace.c:764), iter_iseq=(miniruby`oldbt_iter_iseq at vm_backtrace.c:772), iter_cfunc=(miniruby`oldbt_iter_cfunc at vm_backtrace.c:785), arg=0x00007ffeefbfdef8) at vm_backtrace.c:540:6
    frame #7: 0x0000000100320641 miniruby`rb_backtrace_print_as_bugreport at vm_backtrace.c:849:5
    frame #8: 0x0000000100325c20 miniruby`rb_vm_bugreport(ctx=0x0000000000000000) at vm_dump.c:946:2
    frame #9: 0x0000000100337885 miniruby`rb_bug(fmt="%s: %s (%s)") at error.c:660:5
    frame #10: 0x00000001000aa9c5 miniruby`rb_bug_errno(mesg="pthread_mutex_lock", errno_arg=22) at error.c:691:13
    frame #11: 0x000000010029ba6b miniruby`rb_native_mutex_lock(lock=0x0000000101809748) at thread_pthread.c:404:2
    frame #12: 0x000000010029db65 miniruby`rb_nativethread_lock_lock(lock=0x0000000101809748) at thread.c:454:5
    frame #13: 0x000000010032affc miniruby`rb_postponed_job_flush(vm=0x0000000101809400) at vm_trace.c:1672:5
    frame #14: 0x000000010029f875 miniruby`rb_threadptr_execute_interrupts(th=0x0000000101106f80, blocking_timing=0) at thread.c:2243:6
    frame #15: 0x00000001003013a1 miniruby`rb_vm_check_ints(ec=0x0000000101107210) at vm_core.h:1822:2
    frame #16: 0x00000001002e1e08 miniruby`vm_pop_frame(ec=0x0000000101107210, cfp=0x0000000101319f90, ep=0x000000010121a028) at vm_insnhelper.c:386:5
    frame #17: 0x00000001002e1dc9 miniruby`rb_vm_pop_frame(ec=0x0000000101107210) at vm_insnhelper.c:395:5
    frame #18: 0x000000010031c2d6 miniruby`vm_call0_cfunc_with_frame(ec=0x0000000101107210, calling=0x00007ffeefbfeee0, cd=0x00007ffeefbfeed0, argv=0x00007ffeefbff030) at vm_eval.c:100:2
    frame #19: 0x000000010031b9fd miniruby`vm_call0_cfunc(ec=0x0000000101107210, calling=0x00007ffeefbfeee0, cd=0x00007ffeefbfeed0, argv=0x00007ffeefbff030) at vm_eval.c:111:12
    frame #20: 0x00000001002f394a miniruby`vm_call0_body(ec=0x0000000101107210, calling=0x00007ffeefbfeee0, cd=0x00007ffeefbfeed0, argv=0x00007ffeefbff030) at vm_eval.c:146:15
    frame #21: 0x00000001002f3724 miniruby`rb_vm_call0(ec=0x0000000101107210, recv=4321214240, id=3969, argc=1, argv=0x00007ffeefbff030, me=0x0000000101907200, kw_splat=0) at vm_eval.c:59:12
    frame #22: 0x00000001002f4169 miniruby`rb_vm_call_kw(ec=0x0000000101107210, recv=4321214240, id=3969, argc=1, argv=0x00007ffeefbff030, me=0x0000000101907200, kw_splat=0) at vm_eval.c:239:12
    frame #23: 0x000000010031c62d miniruby`rb_call0(ec=0x0000000101107210, recv=4321214240, mid=3969, argc=1, argv=0x00007ffeefbff030, call_scope=CALL_FCALL, self=8) at vm_eval.c:361:12
    frame #24: 0x00000001002f5330 miniruby`rb_call(recv=4321214240, mid=3969, argc=1, argv=0x00007ffeefbff030, scope=CALL_FCALL) at vm_eval.c:689:12
    frame #25: 0x00000001002f56e5 miniruby`rb_funcall(recv=4321214240, mid=3969, n=1) at vm_eval.c:915:12
    frame #26: 0x0000000100037acd miniruby`rb_class_inherited(super=4321214240, klass=4321376976) at class.c:710:12
    frame #27: 0x000000010003818f miniruby`rb_define_class_id_under(outer=4320184456, id=22411, super=4321214240) at class.c:832:5
    frame #28: 0x0000000100037e38 miniruby`rb_define_class_under(outer=4320184456, name="WeakMap", super=4321214240) at class.c:782:12
    frame #29: 0x00000001000da0ca miniruby`Init_GC at gc.c:12066:22
    frame #30: 0x00000001000fb1cd miniruby`rb_call_inits at inits.c:61:5
    frame #31: 0x00000001000b5e60 miniruby`ruby_setup at eval.c:91:2
    frame #32: 0x00000001000b5efd miniruby`ruby_init at eval.c:108:17
    frame #33: 0x00000001000016a8 miniruby`main(argc=2, argv=0x00007ffeefbff610) at main.c:49:2
    frame #34: 0x00007fff718dccc9 libdyld.dylib`start + 1

[peterzhu2118]

FYI CI is completely broken because my code is broken on Linux. I'm currently looking into the issue.

[eightbitraptor]

Closed in favour of #16 as I updated this to be on top of master