[pull] main from python:main

Doc/library/ctypes.rst

@@ -14,6 +14,14 @@ used to wrap these libraries in pure Python.
 
 .. include:: ../includes/optional-module.rst
 
+.. warning::
+
+   :mod:`!ctypes` provides low-level access to native libraries and the
+   process's memory, bypassing Python's safety mechanisms and allowing
+   execution of arbitrary native code.
+   Incorrect use can corrupt data and objects, reveal sensitive information,
+   cause crashes, or otherwise compromise the running process.
+
 
 .. _ctypes-ctypes-tutorial:
 
@@ -198,10 +206,8 @@ argument values::
    OSError: exception: access violation reading 0x00000020
    >>>
 
-There are, however, enough ways to crash Python with :mod:`!ctypes`, so you
-should be careful anyway.  The :mod:`faulthandler` module can be helpful in
-debugging crashes (e.g. from segmentation faults produced by erroneous C library
-calls).
+The :mod:`faulthandler` module can help debug crashes,
+such as segmentation faults produced by erroneous C library calls.
 
 ``None``, integers, bytes objects and (unicode) strings are the only native
 Python objects that can directly be used as parameters in these function calls.

Include/internal/pycore_interp_structs.h

@@ -1001,7 +1001,7 @@ struct _is {
     struct ast_state ast;
     struct types_state types;
     struct callable_cache callable_cache;
-    PyObject *common_consts[NUM_COMMON_CONSTANTS];
+    _PyStackRef common_consts[NUM_COMMON_CONSTANTS];
     bool jit;
     bool compiling;
 

Include/internal/pycore_stackref.h

@@ -263,6 +263,18 @@ _PyStackRef_DUP(_PyStackRef ref, const char *filename, int linenumber)
 }
 #define PyStackRef_DUP(REF) _PyStackRef_DUP(REF, __FILE__, __LINE__)
 
+static inline _PyStackRef
+_PyStackRef_DupImmortal(_PyStackRef ref, const char *filename, int linenumber)
+{
+    assert(!PyStackRef_IsError(ref));
+    assert(!PyStackRef_IsTaggedInt(ref));
+    assert(!PyStackRef_RefcountOnObject(ref));
+    PyObject *obj = _Py_stackref_get_object(ref);
+    assert(_Py_IsImmortal(obj));
+    return _Py_stackref_create(obj, Py_TAG_REFCNT, filename, linenumber);
+}
+#define PyStackRef_DupImmortal(REF) _PyStackRef_DupImmortal((REF), __FILE__, __LINE__)
+
 static inline void
 _PyStackRef_CLOSE_SPECIALIZED(_PyStackRef ref, destructor destruct, const char *filename, int linenumber)
 {
@@ -633,6 +645,15 @@ PyStackRef_DUP(_PyStackRef ref)
 }
 #endif
 
+static inline _PyStackRef
+PyStackRef_DupImmortal(_PyStackRef ref)
+{
+    assert(!PyStackRef_IsNull(ref));
+    assert(!PyStackRef_RefcountOnObject(ref));
+    assert(_Py_IsImmortal(BITS_TO_PTR_MASKED(ref)));
+    return ref;
+}
+
 static inline bool
 PyStackRef_IsHeapSafe(_PyStackRef ref)
 {

InternalDocs/qsbr.md

@@ -101,15 +101,39 @@ Periodically, a polling mechanism processes this deferred-free list:
 
 To reduce memory contention from frequent updates to the global `wr_seq`, its
 advancement is sometimes deferred. Instead of incrementing `wr_seq` on every
-reclamation request, each thread tracks its number of deferrals locally. Once
-the deferral count reaches a limit (QSBR_DEFERRED_LIMIT, currently 10), the
-thread advances the global `wr_seq` and resets its local count.
-
-When an object is added to the deferred-free list, its qsbr_goal is set to
-`wr_seq` + 2. By setting the goal to the next sequence value, we ensure it's safe
-to defer the global counter advancement. This optimization improves runtime
-speed but may increase peak memory usage by slightly delaying when memory can
-be reclaimed.
+reclamation request, the object's qsbr_goal is set to `wr_seq` + 2 (the value
+the counter *would* take on its next advance) without actually advancing the
+global counter. This is safe because the goal still corresponds to a future
+sequence value that no thread has yet observed as quiescent.
+
+Whether to actually advance `wr_seq` is decided per request, based on how
+much memory and how many items the calling thread has already deferred since
+its last advance:
+
+* For deferred object frees (`_PyMem_FreeDelayed`), the thread tracks both a
+  count (`deferred_count`) and an estimate of the held memory
+  (`deferred_memory`). The global `wr_seq` is advanced when the freed block
+  is larger than `QSBR_FREE_MEM_LIMIT` (1 MiB), when the accumulated deferred
+  memory exceeds that limit, or when the count exceeds `QSBR_DEFERRED_LIMIT`
+  (127, sized so a chunk of work items is processed before it overflows).
+  Crossing any of these thresholds also sets a per-thread `should_process`
+  flag, signalling that the deferred-free list should be drained.
+
+* For mimalloc pages held by QSBR, the thread tracks `deferred_page_memory`
+  and advances `wr_seq` when either the individual page or the accumulated
+  page memory exceeds `QSBR_PAGE_MEM_LIMIT` (4096 * 20 bytes). Advancing
+  promptly here matters because a held page cannot be reused for a different
+  size class or by a different thread.
+
+Processing of the deferred-free list normally happens from the eval breaker
+(rather than from inside `_PyMem_FreeDelayed`), which gives the global
+`rd_seq` a better chance to have advanced far enough that items can actually
+be freed. `_PyMem_ProcessDelayed` is still called from the free path as a
+safety valve when a work-item chunk fills up.
+
+This optimization improves runtime speed but may increase peak memory usage
+by slightly delaying when memory can be reclaimed; the size-based thresholds
+above bound that extra memory.
 
 
 ## Limitations

Python/bytecodes.c

@@ -1974,7 +1974,7 @@ dummy_func(
         inst(LOAD_COMMON_CONSTANT, ( -- value)) {
             // Keep in sync with _common_constants in opcode.py
             assert(oparg < NUM_COMMON_CONSTANTS);
-            value = PyStackRef_FromPyObjectNew(tstate->interp->common_consts[oparg]);
+            value = PyStackRef_DupImmortal(tstate->interp->common_consts[oparg]);
         }
 
         inst(LOAD_BUILD_CLASS, ( -- bc)) {

Python/flowgraph.c

@@ -11,6 +11,7 @@
 #include "pycore_opcode_utils.h"
 #include "pycore_opcode_metadata.h" // OPCODE_HAS_ARG, etc
 #include "pycore_pystate.h"         // _PyInterpreterState_GET()
+#include "pycore_stackref.h"        // PyStackRef_AsPyObjectBorrow()
 
 #include <stdbool.h>
 
@@ -1330,7 +1331,8 @@ get_const_value(int opcode, int oparg, PyObject *co_consts)
     }
     if (opcode == LOAD_COMMON_CONSTANT) {
         assert(oparg < NUM_COMMON_CONSTANTS);
-        return Py_NewRef(_PyInterpreterState_GET()->common_consts[oparg]);
+        return PyStackRef_AsPyObjectBorrow(
+            _PyInterpreterState_GET()->common_consts[oparg]);
     }
 
     if (constant == NULL) {

Python/optimizer_bytecodes.c

@@ -2,6 +2,7 @@
 #include "pycore_long.h"
 #include "pycore_opcode_utils.h"
 #include "pycore_optimizer.h"
+#include "pycore_stackref.h"
 #include "pycore_typeobject.h"
 #include "pycore_uops.h"
 #include "pycore_uop_ids.h"
@@ -870,15 +871,11 @@ dummy_func(void) {
 
     op(_LOAD_COMMON_CONSTANT, (-- value)) {
         assert(oparg < NUM_COMMON_CONSTANTS);
-        PyObject *val = _PyInterpreterState_GET()->common_consts[oparg];
-        if (_Py_IsImmortal(val)) {
-            ADD_OP(_LOAD_CONST_INLINE_BORROW, 0, (uintptr_t)val);
-            value = PyJitRef_Borrow(sym_new_const(ctx, val));
-        }
-        else {
-            ADD_OP(_LOAD_CONST_INLINE, 0, (uintptr_t)val);
-            value = sym_new_const(ctx, val);
-        }
+        PyObject *val = PyStackRef_AsPyObjectBorrow(
+            _PyInterpreterState_GET()->common_consts[oparg]);
+        assert(_Py_IsImmortal(val));
+        ADD_OP(_LOAD_CONST_INLINE_BORROW, 0, (uintptr_t)val);
+        value = PyJitRef_Borrow(sym_new_const(ctx, val));
     }
 
     op(_LOAD_SMALL_INT, (-- value)) {

Python/pylifecycle.c

@@ -28,6 +28,7 @@
 #include "pycore_runtime.h"       // _Py_ID()
 #include "pycore_runtime_init.h"  // _PyRuntimeState_INIT
 #include "pycore_setobject.h"     // _PySet_NextEntry()
+#include "pycore_stackref.h"      // PyStackRef_FromPyObjectBorrow()
 #include "pycore_stats.h"         // _PyStats_InterpInit()
 #include "pycore_sysmodule.h"     // _PySys_ClearAttrString()
 #include "pycore_traceback.h"     // PyUnstable_TracebackThreads()
@@ -878,25 +879,28 @@ pycore_init_builtins(PyThreadState *tstate)
         goto error;
     }
 
-    interp->common_consts[CONSTANT_ASSERTIONERROR] = PyExc_AssertionError;
-    interp->common_consts[CONSTANT_NOTIMPLEMENTEDERROR] = PyExc_NotImplementedError;
-    interp->common_consts[CONSTANT_BUILTIN_TUPLE] = (PyObject *)&PyTuple_Type;
-    interp->common_consts[CONSTANT_BUILTIN_ALL] = all;
-    interp->common_consts[CONSTANT_BUILTIN_ANY] = any;
-    interp->common_consts[CONSTANT_BUILTIN_LIST] = (PyObject *)&PyList_Type;
-    interp->common_consts[CONSTANT_BUILTIN_SET] = (PyObject *)&PySet_Type;
-    interp->common_consts[CONSTANT_NONE] = Py_None;
-    interp->common_consts[CONSTANT_EMPTY_STR] =
+    PyObject *common_objs[NUM_COMMON_CONSTANTS] = {NULL};
+    common_objs[CONSTANT_ASSERTIONERROR] = PyExc_AssertionError;
+    common_objs[CONSTANT_NOTIMPLEMENTEDERROR] = PyExc_NotImplementedError;
+    common_objs[CONSTANT_BUILTIN_TUPLE] = (PyObject *)&PyTuple_Type;
+    common_objs[CONSTANT_BUILTIN_ALL] = all;
+    common_objs[CONSTANT_BUILTIN_ANY] = any;
+    common_objs[CONSTANT_BUILTIN_LIST] = (PyObject *)&PyList_Type;
+    common_objs[CONSTANT_BUILTIN_SET] = (PyObject *)&PySet_Type;
+    common_objs[CONSTANT_NONE] = Py_None;
+    common_objs[CONSTANT_EMPTY_STR] =
         Py_GetConstantBorrowed(Py_CONSTANT_EMPTY_STR);
-    interp->common_consts[CONSTANT_TRUE] = Py_True;
-    interp->common_consts[CONSTANT_FALSE] = Py_False;
-    interp->common_consts[CONSTANT_MINUS_ONE] =
+    common_objs[CONSTANT_TRUE] = Py_True;
+    common_objs[CONSTANT_FALSE] = Py_False;
+    common_objs[CONSTANT_MINUS_ONE] =
         (PyObject *)&_PyLong_SMALL_INTS[_PY_NSMALLNEGINTS - 1];
-    interp->common_consts[CONSTANT_BUILTIN_FROZENSET] = (PyObject *)&PyFrozenSet_Type;
-    interp->common_consts[CONSTANT_EMPTY_TUPLE] =
+    common_objs[CONSTANT_BUILTIN_FROZENSET] = (PyObject *)&PyFrozenSet_Type;
+    common_objs[CONSTANT_EMPTY_TUPLE] =
         Py_GetConstantBorrowed(Py_CONSTANT_EMPTY_TUPLE);
     for (int i = 0; i < NUM_COMMON_CONSTANTS; i++) {
-        assert(interp->common_consts[i] != NULL);
+        assert(common_objs[i] != NULL);
+        _Py_SetImmortal(common_objs[i]);
+        interp->common_consts[i] = PyStackRef_FromPyObjectBorrow(common_objs[i]);
     }
 
     PyObject *list_append = _PyType_Lookup(&PyList_Type, &_Py_ID(append));

Python/pystate.c

@@ -12,16 +12,17 @@
 #include "pycore_freelist.h"      // _PyObject_ClearFreeLists()
 #include "pycore_initconfig.h"    // _PyStatus_OK()
 #include "pycore_interpframe.h"   // _PyThreadState_HasStackSpace()
-#include "pycore_object.h"        // _PyType_InitCache()
+#include "pycore_object.h"        // _PyType_InitCache(), _Py_ClearImmortal()
 #include "pycore_obmalloc.h"      // _PyMem_obmalloc_state_on_heap()
+#include "pycore_opcode_utils.h"  // NUM_COMMON_CONSTANTS
 #include "pycore_optimizer.h"     // JIT_CLEANUP_THRESHOLD
 #include "pycore_parking_lot.h"   // _PyParkingLot_AfterFork()
 #include "pycore_pyerrors.h"      // _PyErr_Clear()
 #include "pycore_pylifecycle.h"   // _PyAST_Fini()
 #include "pycore_pymem.h"         // _PyMem_DebugEnabled()
 #include "pycore_runtime.h"       // _PyRuntime
 #include "pycore_runtime_init.h"  // _PyRuntimeState_INIT
-#include "pycore_stackref.h"      // Py_STACKREF_DEBUG
+#include "pycore_stackref.h"      // PyStackRef_AsPyObjectBorrow()
 #include "pycore_stats.h"         // FT_STAT_WORLD_STOP_INC()
 #include "pycore_time.h"          // _PyTime_Init()
 #include "pycore_uniqueid.h"      // _PyObject_FinalizePerThreadRefcounts()
@@ -778,6 +779,36 @@ extern void
 _Py_stackref_report_leaks(PyInterpreterState *interp);
 #endif
 
+static int
+common_const_is_initialized(_PyStackRef ref)
+{
+#if !defined(Py_GIL_DISABLED) && defined(Py_STACKREF_DEBUG)
+    return !PyStackRef_IsNull(ref);
+#else
+    return ref.bits != 0 && !PyStackRef_IsNull(ref);
+#endif
+}
+
+
+static void
+common_constants_clear(PyInterpreterState *interp)
+{
+    for (int i = 0; i < NUM_COMMON_CONSTANTS; i++) {
+        _PyStackRef ref = interp->common_consts[i];
+        if (!common_const_is_initialized(ref)) {
+            continue;
+        }
+        PyObject *obj = PyStackRef_AsPyObjectBorrow(ref);
+        PyStackRef_XCLOSE(ref);
+        interp->common_consts[i] = PyStackRef_NULL;
+        // Refcount reclamation skips heap immortals; release manually.
+        if (_Py_IsImmortal(obj) && !_Py_IsStaticImmortal(obj)) {
+            _Py_ClearImmortal(obj);
+        }
+    }
+}
+
+
 static void
 interpreter_clear(PyInterpreterState *interp, PyThreadState *tstate)
 {
@@ -904,6 +935,7 @@ interpreter_clear(PyInterpreterState *interp, PyThreadState *tstate)
     PyDict_Clear(interp->builtins);
     Py_CLEAR(interp->sysdict);
     Py_CLEAR(interp->builtins);
+    common_constants_clear(interp);
 
 #if !defined(Py_GIL_DISABLED) && defined(Py_STACKREF_DEBUG)
 #  ifdef Py_STACKREF_CLOSE_DEBUG

Tools/cases_generator/analyzer.py

@@ -609,6 +609,7 @@ def has_error_without_pop(op: parser.CodeDef) -> bool:
     "PyStackRef_CLEAR",
     "PyStackRef_CLOSE_SPECIALIZED",
     "PyStackRef_DUP",
+    "PyStackRef_DupImmortal",
     "PyStackRef_False",
     "PyStackRef_FromPyObjectBorrow",
     "PyStackRef_FromPyObjectNew",