rt: Extract prepare_valgrind_stack from register_valgrind_stack

src/rt/rust_stack.cpp

@@ -8,6 +8,10 @@ register_valgrind_stack(stk_seg *stk) {
     stk->valgrind_id =
         VALGRIND_STACK_REGISTER(&stk->data[0],
                                 stk->end);
+}
+
+void
+prepare_valgrind_stack(stk_seg *stk) {
 #ifndef NVALGRIND
     // Establish that the stack is accessible.  This must be done when reusing
     // old stack segments, since the act of popping the stack previously

src/rt/rust_stack.h

@@ -42,6 +42,9 @@ destroy_stack(T allocer, stk_seg *stk) {
 void
 register_valgrind_stack(stk_seg *stk);
 
+void
+prepare_valgrind_stack(stk_seg *stk);
+
 void
 deregister_valgrind_stack(stk_seg *stk);
 

src/rt/rust_task.cpp

@@ -568,6 +568,7 @@ rust_task::new_stack(size_t requested_sz) {
             stk = stk->prev;
             A(thread, stk->prev == NULL, "Bogus stack ptr");
             register_valgrind_stack(stk);
+            prepare_valgrind_stack(stk);
             return;
         } else {
             LOG(this, mem, "existing stack is not big enough");
@@ -599,6 +600,7 @@ rust_task::new_stack(size_t requested_sz) {
 
     stk = new_stk;
     register_valgrind_stack(stk);
+    prepare_valgrind_stack(stk);
     total_stack_sz += user_stack_size(new_stk);
 }
 

src/rt/rust_task_thread.cpp

@@ -373,6 +373,7 @@ rust_task_thread::prepare_c_stack() {
     if (!cached_c_stack) {
         cached_c_stack = create_stack(kernel, C_STACK_SIZE);
         register_valgrind_stack(cached_c_stack);
+        prepare_valgrind_stack(cached_c_stack);
     }
 }