Revert "Fix potential hang when joining threads."

This reverts commit 13f8521c63.

http://rubyci.s3.amazonaws.com/solaris11-gcc/ruby-master/log/20210727T230009Z.fail.html.gz
http://rubyci.s3.amazonaws.com/solaris11-sunc/ruby-master/log/20210728T000009Z.fail.html.gz

This revert is to confirm whether the commit is the cause.
If the failures consistently occur after this revert, I'll
reintroduce the commit.

test/fiber/scheduler.rb

@@ -112,10 +112,8 @@ class Scheduler
 
     self.run
   ensure
-    if @urgent
+    @urgent.each(&:close)
-      @urgent.each(&:close)
+    @urgent = nil
-      @urgent = nil
-    end
 
     @closed = true
 
@@ -242,13 +240,3 @@ class BrokenUnblockScheduler < Scheduler
     raise "Broken unblock!"
   end
 end
-
-class SleepingUnblockScheduler < Scheduler
-  # This method is invoked when the thread is exiting.
-  def unblock(blocker, fiber)
-    super
-
-    # This changes the current thread state to `THREAD_RUNNING` which causes `thread_join_sleep` to hang.
-    sleep(0.1)
-  end
-end

test/fiber/test_thread.rb

@@ -66,18 +66,4 @@ class TestFiberThread < Test::Unit::TestCase
       thread.join
     end
   end
-
-  def test_thread_join_hang
-    thread = Thread.new do
-      scheduler = SleepingUnblockScheduler.new
-
-      Fiber.set_scheduler scheduler
-
-      Fiber.schedule do
-        Thread.new{sleep(0.01)}.value
-      end
-    end
-
-    thread.join
-  end
 end

thread.c

@@ -632,7 +632,6 @@ thread_cleanup_func_before_exec(void *th_ptr)
 {
     rb_thread_t *th = th_ptr;
     th->status = THREAD_KILLED;
-
     // The thread stack doesn't exist in the forked process:
     th->ec->machine.stack_start = th->ec->machine.stack_end = NULL;
 
@@ -818,9 +817,6 @@ thread_start_func_2(rb_thread_t *th, VALUE *stack_start)
 
     thread_debug("thread start (get lock): %p\n", (void *)th);
 
-    // Ensure that we are not joinable.
-    VM_ASSERT(th->value == Qundef);
-
     EC_PUSH_TAG(th->ec);
 
     if ((state = EC_EXEC_TAG()) == TAG_NONE) {
@@ -861,12 +857,6 @@ thread_start_func_2(rb_thread_t *th, VALUE *stack_start)
         th->value = Qnil;
     }
 
-    // The thread is effectively finished and can be joined.
-    VM_ASSERT(th->value != Qundef);
-
-    rb_threadptr_join_list_wakeup(th);
-    rb_threadptr_unlock_all_locking_mutexes(th);
-
     if (th->invoke_type == thread_invoke_type_ractor_proc) {
         rb_thread_terminate_all(th);
         rb_ractor_teardown(th->ec);
@@ -884,6 +874,9 @@ thread_start_func_2(rb_thread_t *th, VALUE *stack_start)
         rb_threadptr_raise(ractor_main_th, 1, &errinfo);
     }
 
+    rb_threadptr_join_list_wakeup(th);
+    rb_threadptr_unlock_all_locking_mutexes(th);
+
     EC_POP_TAG();
 
     rb_ec_clear_current_thread_trace_func(th->ec);
@@ -1160,12 +1153,6 @@ remove_from_join_list(VALUE arg)
 
 static rb_hrtime_t *double2hrtime(rb_hrtime_t *, double);
 
-static int
-thread_finished(rb_thread_t *th)
-{
-    return th->status == THREAD_KILLED || th->value != Qundef;
-}
-
 static VALUE
 thread_join_sleep(VALUE arg)
 {
@@ -1192,7 +1179,7 @@ thread_join_sleep(VALUE arg)
         end = rb_hrtime_add(*limit, rb_hrtime_now());
     }
 
-    while (!thread_finished(target_th)) {
+    while (target_th->status != THREAD_KILLED) {
         VALUE scheduler = rb_fiber_scheduler_current();
 
         if (scheduler != Qnil) {

vm.c

@@ -3081,8 +3081,6 @@ th_init(rb_thread_t *th, VALUE self)
     th->thread_id_string[0] = '\0';
 #endif
 
-    th->value = Qundef;
-
 #if OPT_CALL_THREADED_CODE
     th->retval = Qundef;
 #endif
@@ -3095,17 +3093,16 @@ static VALUE
 ruby_thread_init(VALUE self)
 {
     rb_thread_t *th = GET_THREAD();
-    rb_thread_t *target_th = rb_thread_ptr(self);
+    rb_thread_t *targe_th = rb_thread_ptr(self);
     rb_vm_t *vm = th->vm;
 
-    target_th->vm = vm;
+    targe_th->vm = vm;
-    th_init(target_th, self);
+    th_init(targe_th, self);
-
-    target_th->top_wrapper = 0;
-    target_th->top_self = rb_vm_top_self();
-    target_th->ec->root_svar = Qfalse;
-    target_th->ractor = th->ractor;
 
+    targe_th->top_wrapper = 0;
+    targe_th->top_self = rb_vm_top_self();
+    targe_th->ec->root_svar = Qfalse;
+    targe_th->ractor = th->ractor;
     return self;
 }