[libcxx-commits] [libcxx] [libc++] fix condition_variable_any hangs on stop_request (PR #77127)

[Louis Dionne via libcxx-commits]

================
@@ -256,23 +262,60 @@ condition_variable_any::wait_for(_Lock& __lock, const chrono::duration<_Rep, _Pe
 #  if _LIBCPP_STD_VER >= 20 && !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_STOP_TOKEN)
 
 template <class _Lock, class _Predicate>
-bool condition_variable_any::wait(_Lock& __lock, stop_token __stoken, _Predicate __pred) {
-  while (!__stoken.stop_requested()) {
+bool condition_variable_any::wait(_Lock& __user_lock, stop_token __stoken, _Predicate __pred) {
+  // It is not safe to call the destructor on the other thread while waiting,
+  // even if we copy the shared_ptr<mutex> inside the function,
+  // because the stop_callback needs the internal cv.
+  // In order to make it work, we need to change the ABI to make both
+  // mutex and internal cv to be hold inside the shared_ptr, and
+  // make a local copy inside this function
+
+  if (__stoken.stop_requested())
+    return __pred();
+  std::stop_callback __cb(__stoken, [this] { notify_all(); });
----------------
ldionne wrote:

```suggestion
  stop_callback __cb(__stoken, [this] { notify_all(); });
```

https://github.com/llvm/llvm-project/pull/77127