gh-101659: Isolate "obmalloc" State to Each Interpreter (gh-101660)

This is strictly about moving the "obmalloc" runtime state from
`_PyRuntimeState` to `PyInterpreterState`.  Doing so improves isolation
between interpreters, specifically most of the memory (incl. objects)
allocated for each interpreter's use.  This is important for a
per-interpreter GIL, but such isolation is valuable even without it.

FWIW, a per-interpreter obmalloc is the proverbial
canary-in-the-coalmine when it comes to the isolation of objects between
interpreters.  Any object that leaks (unintentionally) to another
interpreter is highly likely to cause a crash (on debug builds at
least).  That's a useful thing to know, relative to interpreter
isolation.

1 files changed, 13 insertions, 4 deletions

diff --git a/Python/pystate.c b/Python/pystate.c
index d108cfc7e50..b2ef7e2ddde 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -671,6 +671,14 @@ init_interpreter(PyInterpreterState *interp,
     assert(next != NULL || (interp == runtime->interpreters.main));
     interp->next = next;
 
+    /* Initialize obmalloc, but only for subinterpreters,
+       since the main interpreter is initialized statically. */
+    if (interp != &runtime->_main_interpreter) {
+        poolp temp[OBMALLOC_USED_POOLS_SIZE] = \
+                _obmalloc_pools_INIT(interp->obmalloc.pools);
+        memcpy(&interp->obmalloc.pools.used, temp, sizeof(temp));
+    }
+
     _PyEval_InitState(&interp->ceval, pending_lock);
     _PyGC_InitState(&interp->gc);
     PyConfig_InitPythonConfig(&interp->config);
@@ -941,11 +949,12 @@ PyInterpreterState_Delete(PyInterpreterState *interp)
 
     _PyEval_FiniState(&interp->ceval);
 
-#ifdef Py_REF_DEBUG
-    // XXX This call should be done at the end of clear_interpreter(),
+    // XXX These two calls should be done at the end of clear_interpreter(),
     // but currently some objects get decref'ed after that.
+#ifdef Py_REF_DEBUG
     _PyInterpreterState_FinalizeRefTotal(interp);
 #endif
+    _PyInterpreterState_FinalizeAllocatedBlocks(interp);
 
     HEAD_LOCK(runtime);
     PyInterpreterState **p;
@@ -2320,11 +2329,11 @@ _PyCrossInterpreterData_InitWithSize(_PyCrossInterpreterData *data,
     // where it was allocated, so the interpreter is required.
     assert(interp != NULL);
     _PyCrossInterpreterData_Init(data, interp, NULL, obj, new_object);
-    data->data = PyMem_Malloc(size);
+    data->data = PyMem_RawMalloc(size);
     if (data->data == NULL) {
         return -1;
     }
-    data->free = PyMem_Free;
+    data->free = PyMem_RawFree;
     return 0;
 }