fix Ractor.yield(obj, move: true)

Ractor.yield(obj, move: true) and
Ractor.select(..., yield_value: obj, move: true) tried to yield a
value with move semantices, but if the trial is faild, the obj
should not become a moved object.

To keep this rule, `wait_moving` wait status is introduced.

New yield/take process:
(1) If a ractor tried to yield (move:true), make taking racotr's
    wait status `wait_moving` and make a moved object by
    `ractor_move(obj)` and wakeup taking ractor.
(2) If a ractor tried to take a message from a ractor waiting fo
    yielding (move:true), wakeup the ractor and wait for (1).

Author: ko1

bootstraptest/test_ractor.rb

@@ -709,6 +709,31 @@ def check obj1
   end
 }
 
+# yield/move should not make moved object when the yield is not succeeded
+assert_equal '"str"', %q{
+  R = Ractor.new{}
+  M = Ractor.current
+  r = Ractor.new do
+    s = 'str'
+    selected_r, v = Ractor.select R, yield_value: s, move: true
+    raise if selected_r != R # taken from R
+    M.send s.inspect # s should not be a moved object
+  end
+
+  Ractor.receive
+}
+
+# yield/move can fail
+assert_equal "allocator undefined for Thread", %q{
+  r = Ractor.new do
+    obj = Thread.new{}
+    Ractor.yield obj
+  rescue => e
+    e.message
+  end
+  r.take
+}
+
 # Access to global-variables are prohibited
 assert_equal 'can not access global variables $gv from non-main Ractors', %q{
   $gv = 1

ractor.c

@@ -916,7 +916,7 @@ static VALUE ractor_move(VALUE obj); // in this file
 static VALUE ractor_copy(VALUE obj); // in this file
 
 static void
-ractor_basket_setup(rb_execution_context_t *ec, struct rb_ractor_basket *basket, VALUE obj, VALUE move, bool exc, bool is_will)
+ractor_basket_setup(rb_execution_context_t *ec, struct rb_ractor_basket *basket, VALUE obj, VALUE move, bool exc, bool is_will, bool is_yield)
 {
     basket->sender = rb_ec_ractor_ptr(ec)->pub.self;
     basket->exception = exc;
@@ -935,15 +935,21 @@ ractor_basket_setup(rb_execution_context_t *ec, struct rb_ractor_basket *basket,
     }
     else {
         basket->type = basket_type_move;
-        basket->v = ractor_move(obj);
+
+        if (is_yield) {
+            basket->v = obj; // call ractor_move() when yielding timing.
+        }
+        else {
+            basket->v = ractor_move(obj);
+        }
     }
 }
 
 static VALUE
 ractor_send(rb_execution_context_t *ec, rb_ractor_t *r, VALUE obj, VALUE move)
 {
     struct rb_ractor_basket basket;
-    ractor_basket_setup(ec, &basket, obj, move, false, false);
+    ractor_basket_setup(ec, &basket, obj, move, false, false, false);
     ractor_send_basket(ec, r, &basket);
     return r->pub.self;
 }
@@ -958,17 +964,23 @@ ractor_try_take(rb_execution_context_t *ec, rb_ractor_t *r)
 
     RACTOR_LOCK(r);
     {
-        if (ractor_wakeup(r, wait_yielding, wakeup_by_take)) {
+        if (ractor_sleeping_by(r, wait_yielding)) {
+            MAYBE_UNUSED(bool) wakeup_result;
             VM_ASSERT(r->sync.wait.yielded_basket.type != basket_type_none);
-            basket = r->sync.wait.yielded_basket;
-            ractor_basket_clear(&r->sync.wait.yielded_basket);
+
+            if (r->sync.wait.yielded_basket.type == basket_type_move) {
+                wakeup_result = ractor_wakeup(r, wait_yielding, wakeup_by_retry);
+            }
+            else {
+                wakeup_result = ractor_wakeup(r, wait_yielding, wakeup_by_take);
+                basket = r->sync.wait.yielded_basket;
+                ractor_basket_clear(&r->sync.wait.yielded_basket);
+            }
+            VM_ASSERT(wakeup_result);
         }
         else if (r->sync.outgoing_port_closed) {
             closed = true;
         }
-        else {
-            // not reached.
-        }
     }
     RACTOR_UNLOCK(r);
 
@@ -985,6 +997,12 @@ ractor_try_take(rb_execution_context_t *ec, rb_ractor_t *r)
     }
 }
 
+static VALUE
+ractor_yield_move_body(VALUE v)
+{
+    return ractor_move(v);
+}
+
 static bool
 ractor_try_yield(rb_execution_context_t *ec, rb_ractor_t *cr, struct rb_ractor_basket *basket)
 {
@@ -1009,8 +1027,34 @@ ractor_try_yield(rb_execution_context_t *ec, rb_ractor_t *cr, struct rb_ractor_b
 
         RACTOR_LOCK(r);
         {
-            if (ractor_wakeup(r, wait_taking, wakeup_by_yield)) {
+            if (ractor_sleeping_by(r, wait_taking)) {
                 VM_ASSERT(r->sync.wait.taken_basket.type == basket_type_none);
+
+                if (basket->type == basket_type_move) {
+                    enum ractor_wait_status prev_wait_status = r->sync.wait.status;
+                    r->sync.wait.status = wait_moving;
+
+                    RACTOR_UNLOCK(r);
+                    {
+                        int state;
+                        VALUE moved_value = rb_protect(ractor_yield_move_body, basket->v, &state);
+                        if (state) {
+                            r->sync.wait.status = prev_wait_status;
+                            rb_jump_tag(state);
+                        }
+                        else {
+                            basket->v = moved_value;
+                        }
+                    }
+                    RACTOR_LOCK(r);
+
+                    if (!ractor_wakeup(r, wait_moving, wakeup_by_yield)) {
+                        // terminating?
+                    }
+                }
+                else {
+                    ractor_wakeup(r, wait_taking, wakeup_by_yield);
+                }
                 r->sync.wait.taken_basket = *basket;
             }
             else {
@@ -1080,16 +1124,15 @@ ractor_select(rb_execution_context_t *ec, const VALUE *rs, const int rs_len, VAL
     }
     rs = NULL;
 
+  restart:
+
     if (yield_p) {
         actions[rs_len].type = ractor_select_action_yield;
         actions[rs_len].v = Qundef;
         wait_status |= wait_yielding;
-
-        ractor_basket_setup(ec, &cr->sync.wait.yielded_basket, yielded_value, move, false, false);
+        ractor_basket_setup(ec, &cr->sync.wait.yielded_basket, yielded_value, move, false, false, true);
     }
 
-  restart:
-
     // TODO: shuffle actions
 
     while (1) {
@@ -1580,7 +1623,7 @@ ractor_yield_atexit(rb_execution_context_t *ec, rb_ractor_t *cr, VALUE v, bool e
     ASSERT_ractor_unlocking(cr);
 
     struct rb_ractor_basket basket;
-    ractor_basket_setup(ec, &basket, v, Qfalse, exc, true);
+    ractor_basket_setup(ec, &basket, v, Qfalse, exc, true, true /* this flag is ignored because move is Qfalse */);
 
   retry:
     if (ractor_try_yield(ec, cr, &basket)) {

ractor_core.h

@@ -61,6 +61,7 @@ struct rb_ractor_sync {
             wait_receiving = 0x01,
             wait_taking    = 0x02,
             wait_yielding  = 0x04,
+            wait_moving    = 0x08,
         } status;
 
         enum ractor_wakeup_status {