From 58ef74186795c56e3ec86e8c8f351a1d7826638a Mon Sep 17 00:00:00 2001 From: Eric Snow Date: Thu, 3 Aug 2023 13:51:08 -0600 Subject: [PATCH] gh-107080: Fix Py_TRACE_REFS Crashes Under Isolated Subinterpreters (gh-107567) The linked list of objects was a global variable, which broke isolation between interpreters, causing crashes. To solve this, we've moved the linked list to each interpreter. --- Include/internal/pycore_object.h | 4 +- Include/internal/pycore_object_state.h | 13 +++-- Include/internal/pycore_runtime_init.h | 11 ++++ ...-08-02-12-24-51.gh-issue-107080.PNolFU.rst | 4 ++ Objects/object.c | 51 ++++++++++++------- Python/pylifecycle.c | 8 +-- 6 files changed, 62 insertions(+), 29 deletions(-) create mode 100644 Misc/NEWS.d/next/Core and Builtins/2023-08-02-12-24-51.gh-issue-107080.PNolFU.rst diff --git a/Include/internal/pycore_object.h b/Include/internal/pycore_object.h index b730aba9912..76b3cd69cbf 100644 --- a/Include/internal/pycore_object.h +++ b/Include/internal/pycore_object.h @@ -292,8 +292,8 @@ extern void _PyDebug_PrintTotalRefs(void); #ifdef Py_TRACE_REFS extern void _Py_AddToAllObjects(PyObject *op, int force); -extern void _Py_PrintReferences(FILE *); -extern void _Py_PrintReferenceAddresses(FILE *); +extern void _Py_PrintReferences(PyInterpreterState *, FILE *); +extern void _Py_PrintReferenceAddresses(PyInterpreterState *, FILE *); #endif diff --git a/Include/internal/pycore_object_state.h b/Include/internal/pycore_object_state.h index 94005d77881..65feb5af969 100644 --- a/Include/internal/pycore_object_state.h +++ b/Include/internal/pycore_object_state.h @@ -11,17 +11,22 @@ extern "C" { struct _py_object_runtime_state { #ifdef Py_REF_DEBUG Py_ssize_t interpreter_leaks; -#else - int _not_used; #endif + int _not_used; }; struct _py_object_state { #ifdef Py_REF_DEBUG Py_ssize_t reftotal; -#else - int _not_used; #endif +#ifdef Py_TRACE_REFS + /* Head of circular doubly-linked list of all objects. These are linked + * together via the _ob_prev and _ob_next members of a PyObject, which + * exist only in a Py_TRACE_REFS build. + */ + PyObject refchain; +#endif + int _not_used; }; diff --git a/Include/internal/pycore_runtime_init.h b/Include/internal/pycore_runtime_init.h index dcfceef4f17..e89d368be07 100644 --- a/Include/internal/pycore_runtime_init.h +++ b/Include/internal/pycore_runtime_init.h @@ -157,6 +157,7 @@ extern PyTypeObject _PyExc_MemoryError; { .threshold = 10, }, \ }, \ }, \ + .object_state = _py_object_state_INIT(INTERP), \ .dtoa = _dtoa_state_INIT(&(INTERP)), \ .dict_state = _dict_state_INIT, \ .func_state = { \ @@ -186,6 +187,16 @@ extern PyTypeObject _PyExc_MemoryError; .context_ver = 1, \ } +#ifdef Py_TRACE_REFS +# define _py_object_state_INIT(INTERP) \ + { \ + .refchain = {&INTERP.object_state.refchain, &INTERP.object_state.refchain}, \ + } +#else +# define _py_object_state_INIT(INTERP) \ + { 0 } +#endif + // global objects diff --git a/Misc/NEWS.d/next/Core and Builtins/2023-08-02-12-24-51.gh-issue-107080.PNolFU.rst b/Misc/NEWS.d/next/Core and Builtins/2023-08-02-12-24-51.gh-issue-107080.PNolFU.rst new file mode 100644 index 00000000000..5084c854360 --- /dev/null +++ b/Misc/NEWS.d/next/Core and Builtins/2023-08-02-12-24-51.gh-issue-107080.PNolFU.rst @@ -0,0 +1,4 @@ +Trace refs builds (``--with-trace-refs``) were crashing when used with +isolated subinterpreters. The problematic global state has been isolated to +each interpreter. Other fixing the crashes, this change does not affect +users. diff --git a/Objects/object.c b/Objects/object.c index 8caa5fd0af3..c4413a00ede 100644 --- a/Objects/object.c +++ b/Objects/object.c @@ -159,11 +159,8 @@ _PyDebug_PrintTotalRefs(void) { Do not call them otherwise, they do not initialize the object! */ #ifdef Py_TRACE_REFS -/* Head of circular doubly-linked list of all objects. These are linked - * together via the _ob_prev and _ob_next members of a PyObject, which - * exist only in a Py_TRACE_REFS build. - */ -static PyObject refchain = {&refchain, &refchain}; + +#define REFCHAIN(interp) &interp->object_state.refchain /* Insert op at the front of the list of all objects. If force is true, * op is added even if _ob_prev and _ob_next are non-NULL already. If @@ -188,10 +185,11 @@ _Py_AddToAllObjects(PyObject *op, int force) } #endif if (force || op->_ob_prev == NULL) { - op->_ob_next = refchain._ob_next; - op->_ob_prev = &refchain; - refchain._ob_next->_ob_prev = op; - refchain._ob_next = op; + PyObject *refchain = REFCHAIN(_PyInterpreterState_GET()); + op->_ob_next = refchain->_ob_next; + op->_ob_prev = refchain; + refchain->_ob_next->_ob_prev = op; + refchain->_ob_next = op; } } #endif /* Py_TRACE_REFS */ @@ -2229,7 +2227,8 @@ _Py_ForgetReference(PyObject *op) _PyObject_ASSERT_FAILED_MSG(op, "negative refcnt"); } - if (op == &refchain || + PyObject *refchain = REFCHAIN(_PyInterpreterState_GET()); + if (op == refchain || op->_ob_prev->_ob_next != op || op->_ob_next->_ob_prev != op) { _PyObject_ASSERT_FAILED_MSG(op, "invalid object chain"); @@ -2237,12 +2236,12 @@ _Py_ForgetReference(PyObject *op) #ifdef SLOW_UNREF_CHECK PyObject *p; - for (p = refchain._ob_next; p != &refchain; p = p->_ob_next) { + for (p = refchain->_ob_next; p != refchain; p = p->_ob_next) { if (p == op) { break; } } - if (p == &refchain) { + if (p == refchain) { /* Not found */ _PyObject_ASSERT_FAILED_MSG(op, "object not found in the objects list"); @@ -2258,11 +2257,15 @@ _Py_ForgetReference(PyObject *op) * interpreter must be in a healthy state. */ void -_Py_PrintReferences(FILE *fp) +_Py_PrintReferences(PyInterpreterState *interp, FILE *fp) { PyObject *op; + if (interp == NULL) { + interp = _PyInterpreterState_Main(); + } fprintf(fp, "Remaining objects:\n"); - for (op = refchain._ob_next; op != &refchain; op = op->_ob_next) { + PyObject *refchain = REFCHAIN(interp); + for (op = refchain->_ob_next; op != refchain; op = op->_ob_next) { fprintf(fp, "%p [%zd] ", (void *)op, Py_REFCNT(op)); if (PyObject_Print(op, fp, 0) != 0) { PyErr_Clear(); @@ -2274,34 +2277,42 @@ _Py_PrintReferences(FILE *fp) /* Print the addresses of all live objects. Unlike _Py_PrintReferences, this * doesn't make any calls to the Python C API, so is always safe to call. */ +// XXX This function is not safe to use if the interpreter has been +// freed or is in an unhealthy state (e.g. late in finalization). +// The call in Py_FinalizeEx() is okay since the main interpreter +// is statically allocated. void -_Py_PrintReferenceAddresses(FILE *fp) +_Py_PrintReferenceAddresses(PyInterpreterState *interp, FILE *fp) { PyObject *op; + PyObject *refchain = REFCHAIN(interp); fprintf(fp, "Remaining object addresses:\n"); - for (op = refchain._ob_next; op != &refchain; op = op->_ob_next) + for (op = refchain->_ob_next; op != refchain; op = op->_ob_next) fprintf(fp, "%p [%zd] %s\n", (void *)op, Py_REFCNT(op), Py_TYPE(op)->tp_name); } +/* The implementation of sys.getobjects(). */ PyObject * _Py_GetObjects(PyObject *self, PyObject *args) { int i, n; PyObject *t = NULL; PyObject *res, *op; + PyInterpreterState *interp = _PyInterpreterState_GET(); if (!PyArg_ParseTuple(args, "i|O", &n, &t)) return NULL; - op = refchain._ob_next; + PyObject *refchain = REFCHAIN(interp); + op = refchain->_ob_next; res = PyList_New(0); if (res == NULL) return NULL; - for (i = 0; (n == 0 || i < n) && op != &refchain; i++) { + for (i = 0; (n == 0 || i < n) && op != refchain; i++) { while (op == self || op == args || op == res || op == t || (t != NULL && !Py_IS_TYPE(op, (PyTypeObject *) t))) { op = op->_ob_next; - if (op == &refchain) + if (op == refchain) return res; } if (PyList_Append(res, op) < 0) { @@ -2313,6 +2324,8 @@ _Py_GetObjects(PyObject *self, PyObject *args) return res; } +#undef REFCHAIN + #endif diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c index ceca7776a27..7a17f92b550 100644 --- a/Python/pylifecycle.c +++ b/Python/pylifecycle.c @@ -1921,11 +1921,11 @@ Py_FinalizeEx(void) } if (dump_refs) { - _Py_PrintReferences(stderr); + _Py_PrintReferences(tstate->interp, stderr); } if (dump_refs_fp != NULL) { - _Py_PrintReferences(dump_refs_fp); + _Py_PrintReferences(tstate->interp, dump_refs_fp); } #endif /* Py_TRACE_REFS */ @@ -1961,11 +1961,11 @@ Py_FinalizeEx(void) */ if (dump_refs) { - _Py_PrintReferenceAddresses(stderr); + _Py_PrintReferenceAddresses(tstate->interp, stderr); } if (dump_refs_fp != NULL) { - _Py_PrintReferenceAddresses(dump_refs_fp); + _Py_PrintReferenceAddresses(tstate->interp, dump_refs_fp); fclose(dump_refs_fp); } #endif /* Py_TRACE_REFS */