bpo-30860: Consolidate stateful runtime globals. (#3397)

* group the (stateful) runtime globals into various topical structs
* consolidate the topical structs under a single top-level _PyRuntimeState struct
* add a check-c-globals.py script that helps identify runtime globals

Other globals are excluded (see globals.txt and check-c-globals.py).

1 files changed, 46 insertions, 0 deletions

diff --git a/Include/internal/gil.h b/Include/internal/gil.h
new file mode 100644
index 0000000..6139bd2
--- /dev/null
+++ b/Include/internal/gil.h
@@ -0,0 +1,46 @@
+#ifndef Py_INTERNAL_GIL_H
+#define Py_INTERNAL_GIL_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "pyatomic.h"
+
+#include "internal/condvar.h"
+#ifndef Py_HAVE_CONDVAR
+#error You need either a POSIX-compatible or a Windows system!
+#endif
+
+/* Enable if you want to force the switching of threads at least
+   every `interval`. */
+#undef FORCE_SWITCHING
+#define FORCE_SWITCHING
+
+struct _gil_runtime_state {
+    /* microseconds (the Python API uses seconds, though) */
+    unsigned long interval;
+    /* Last PyThreadState holding / having held the GIL. This helps us
+       know whether anyone else was scheduled after we dropped the GIL. */
+    _Py_atomic_address last_holder;
+    /* Whether the GIL is already taken (-1 if uninitialized). This is
+       atomic because it can be read without any lock taken in ceval.c. */
+    _Py_atomic_int locked;
+    /* Number of GIL switches since the beginning. */
+    unsigned long switch_number;
+    /* This condition variable allows one or several threads to wait
+       until the GIL is released. In addition, the mutex also protects
+       the above variables. */
+    PyCOND_T cond;
+    PyMUTEX_T mutex;
+#ifdef FORCE_SWITCHING
+    /* This condition variable helps the GIL-releasing thread wait for
+       a GIL-awaiting thread to be scheduled and take the GIL. */
+    PyCOND_T switch_cond;
+    PyMUTEX_T switch_mutex;
+#endif
+};
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* !Py_INTERNAL_GIL_H */