rgw/asio: add scope guard warn_about_blocking_in_scope

Signed-off-by: Casey Bodley <[email protected]>

Author: cbodley

src/rgw/rgw_asio_thread.h

@@ -15,6 +15,8 @@
 
 #pragma once
 
+#include <assert.h>
+
 class DoutPrefixProvider;
 
 /// indicates whether the current thread is in boost::asio::io_context::run(),
@@ -24,3 +26,14 @@ extern thread_local bool is_asio_thread;
 /// call when an operation will block the calling thread due to an empty
 /// optional_yield. a warning is logged when is_asio_thread is true
 void maybe_warn_about_blocking(const DoutPrefixProvider* dpp);
+
+/// enables warnings while in scope. these scopes must not be nested
+struct warn_about_blocking_in_scope {
+  warn_about_blocking_in_scope() {
+    assert(!is_asio_thread);
+    is_asio_thread = true;
+  }
+  ~warn_about_blocking_in_scope() {
+    is_asio_thread = false;
+  }
+};