Update comments

XuehaiPan · XuehaiPan · commit 552f8b0eb53c · 2026-01-27T03:36:51.000+08:00
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
@@ -740,8 +740,9 @@ class internals_pp_manager {
             }
         }
 
-        // Assume the GIL is held here. May call back into Python.
-        // Create the internals content.
+        // Assume the GIL is held here. May call back into Python. We cannot hold the lock with our
+        // mutex here. So there may be multiple threads creating the content at the same time. Only
+        // one will install its content to pp below. Others will be freed when going out of scope.
         auto tmp = std::unique_ptr<InternalsType>(new InternalsType());
 
         {

Original file line number	Diff line number	Diff line change
`@@ -740,8 +740,9 @@ class internals_pp_manager {`
`740`	`740`	`}`
`741`	`741`	`}`
`742`	`742`
`743`		`- // Assume the GIL is held here. May call back into Python.`
`744`		`- // Create the internals content.`
	`743`	`+ // Assume the GIL is held here. May call back into Python. We cannot hold the lock with our`
	`744`	`+ // mutex here. So there may be multiple threads creating the content at the same time. Only`
	`745`	`+ // one will install its content to pp below. Others will be freed when going out of scope.`
`745`	`746`	`auto tmp = std::unique_ptr<InternalsType>(new InternalsType());`
`746`	`747`
`747`	`748`	`{`