Fix potential hang when joining threads.

If the thread termination invokes user code after `th->status` becomes
`THREAD_KILLED`, and the user unblock function causes that `th->status` to
become something else (e.g. `THREAD_RUNNING`), threads waiting in
`thread_join_sleep` will hang forever. We move the unblock function call
to before the thread status is updated, and allow threads to join as soon
as `th->value` becomes defined.

This reverts commit 6505c77501f1924571b2fe620c5c7b31ede0cd22.

1 files changed, 10 insertions, 7 deletions

diff --git a/vm.c b/vm.c
index b743bbf413..307c5952f4 100644
--- a/vm.c
+++ b/vm.c
@@ -3075,6 +3075,8 @@ 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
@@ -3087,16 +3089,17 @@ static VALUE
 ruby_thread_init(VALUE self)
 {
     rb_thread_t *th = GET_THREAD();
-    rb_thread_t *targe_th = rb_thread_ptr(self);
+    rb_thread_t *target_th = rb_thread_ptr(self);
     rb_vm_t *vm = th->vm;
 
-    targe_th->vm = vm;
-    th_init(targe_th, self);
+    target_th->vm = vm;
+    th_init(target_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;
 }