pythongh-128679: Redesign tracemalloc locking

* tracemalloc_realloc_gil() and tracemalloc_raw_realloc() no longer
  remove the trace on reentrant call.
* _PyTraceMalloc_Stop() unregisters _PyTraceMalloc_TraceRef().
* _PyTraceMalloc_GetTraces() sets the reentrant flag.
* tracemalloc_clear_traces_unlocked() sets the reentrant flag.

Author: vstinner

Include/internal/pycore_object.h

@@ -299,12 +299,6 @@ Py_ssize_t _Py_ExplicitMergeRefcount(PyObject *op, Py_ssize_t extra);
 extern int _PyType_CheckConsistency(PyTypeObject *type);
 extern int _PyDict_CheckConsistency(PyObject *mp, int check_content);
 
-/* Update the Python traceback of an object. This function must be called
-   when a memory block is reused from a free list.
-
-   Internal function called by _Py_NewReference(). */
-extern int _PyTraceMalloc_TraceRef(PyObject *op, PyRefTracerEvent event, void*);
-
 // Fast inlined version of PyType_HasFeature()
 static inline int
 _PyType_HasFeature(PyTypeObject *type, unsigned long feature) {

Include/internal/pycore_tracemalloc.h

@@ -25,7 +25,7 @@ struct _PyTraceMalloc_Config {
     } initialized;
 
     /* Is tracemalloc tracing memory allocations?
-       Variable protected by the GIL */
+       Variable protected by the TABLES_LOCK(). */
     int tracing;
 
     /* limit of the number of frames in a traceback, 1 by default.
@@ -85,14 +85,14 @@ struct _tracemalloc_runtime_state {
     size_t peak_traced_memory;
     /* Hash table used as a set to intern filenames:
        PyObject* => PyObject*.
-       Protected by the GIL */
+       Protected by the TABLES_LOCK(). */
     _Py_hashtable_t *filenames;
     /* Buffer to store a new traceback in traceback_new().
-       Protected by the GIL. */
+       Protected by the TABLES_LOCK(). */
     struct tracemalloc_traceback *traceback;
     /* Hash table used as a set to intern tracebacks:
        traceback_t* => traceback_t*
-       Protected by the GIL */
+       Protected by the TABLES_LOCK(). */
     _Py_hashtable_t *tracebacks;
     /* pointer (void*) => trace (trace_t*).
        Protected by TABLES_LOCK(). */