gh-100227: Make the Global Interned Dict Safe for Isolated Interpreters (gh-102925)

This is effectively two changes.  The first (the bulk of the change) is where we add _Py_AddToGlobalDict() (and _PyRuntime.cached_objects.main_tstate, etc.).  The second (much smaller) change is where we update PyUnicode_InternInPlace() to use _Py_AddToGlobalDict() instead of calling PyDict_SetDefault() directly.

Basically, _Py_AddToGlobalDict() is a wrapper around PyDict_SetDefault() that should be used whenever we need to add a value to a runtime-global dict object (in the few cases where we are leaving the container global rather than moving it to PyInterpreterState, e.g. the interned strings dict).  _Py_AddToGlobalDict() does all the necessary work to make sure the target global dict is shared safely between isolated interpreters.  This is especially important as we move the obmalloc state to each interpreter (gh-101660), as well as, potentially, the GIL (PEP 684).

https://github.com/python/cpython/issues/100227
This commit is contained in:
Eric Snow 2023-03-22 18:30:04 -06:00 committed by GitHub
parent 8709697292
commit 87be8d9522
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GPG Key ID: 4AEE18F83AFDEB23
7 changed files with 204 additions and 30 deletions

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@ -28,6 +28,10 @@ extern "C" {
struct _Py_cached_objects {
PyObject *interned_strings;
/* A thread state tied to the main interpreter,
used exclusively for when a global object (e.g. interned strings)
is resized (i.e. deallocated + allocated) from an arbitrary thread. */
PyThreadState main_tstate;
};
#define _Py_GLOBAL_OBJECT(NAME) \

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@ -127,6 +127,11 @@ PyAPI_FUNC(void) _PyThreadState_Init(
PyThreadState *tstate);
PyAPI_FUNC(void) _PyThreadState_DeleteExcept(PyThreadState *tstate);
extern void _PyThreadState_InitDetached(PyThreadState *, PyInterpreterState *);
extern void _PyThreadState_ClearDetached(PyThreadState *);
extern PyObject * _Py_AddToGlobalDict(PyObject *, PyObject *, PyObject *);
static inline void
_PyThreadState_UpdateTracingState(PyThreadState *tstate)

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@ -59,6 +59,9 @@ extern PyTypeObject _PyExc_MemoryError;
.types = { \
.next_version_tag = 1, \
}, \
.cached_objects = { \
.main_tstate = _PyThreadState_INIT, \
}, \
.static_objects = { \
.singletons = { \
.small_ints = _Py_small_ints_INIT, \

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@ -34,6 +34,7 @@ struct _Py_unicode_runtime_ids {
struct _Py_unicode_runtime_state {
struct _Py_unicode_runtime_ids ids;
/* The interned dict is at _PyRuntime.cached_objects.interned_strings. */
};
/* fs_codec.encoding is initialized to NULL.

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@ -14609,16 +14609,11 @@ PyUnicode_InternInPlace(PyObject **p)
}
PyObject *interned = get_interned_dict();
assert(interned != NULL);
PyObject *t = PyDict_SetDefault(interned, s, s);
if (t == NULL) {
PyErr_Clear();
return;
}
PyObject *t = _Py_AddToGlobalDict(interned, s, s);
if (t != s) {
Py_SETREF(*p, Py_NewRef(t));
if (t != NULL) {
Py_SETREF(*p, Py_NewRef(t));
}
return;
}

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@ -636,6 +636,8 @@ pycore_create_interpreter(_PyRuntimeState *runtime,
return status;
}
_PyThreadState_InitDetached(&runtime->cached_objects.main_tstate, interp);
*tstate_p = tstate;
return _PyStatus_OK();
}
@ -1932,6 +1934,8 @@ Py_FinalizeEx(void)
// XXX Do this sooner during finalization.
// XXX Ensure finalizer errors are handled properly.
_PyThreadState_ClearDetached(&runtime->cached_objects.main_tstate);
finalize_interp_clear(tstate);
finalize_interp_delete(tstate->interp);

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@ -565,6 +565,124 @@ _PyRuntimeState_ReInitThreads(_PyRuntimeState *runtime)
#endif
//---------------
// global objects
//---------------
/* The global objects thread state is meant to be used in a very limited
way and should not be used to actually run any Python code. */
static PyThreadState *
bind_global_objects_state(_PyRuntimeState *runtime)
{
PyThreadState *main_tstate = &runtime->cached_objects.main_tstate;
bind_tstate(main_tstate);
/* Unlike _PyThreadState_Bind(), we do not modify gilstate TSS. */
return main_tstate;
}
static void
unbind_global_objects_state(_PyRuntimeState *runtime)
{
PyThreadState *main_tstate = &runtime->cached_objects.main_tstate;
assert(tstate_is_alive(main_tstate));
assert(!main_tstate->_status.active);
assert(gilstate_tss_get(runtime) != main_tstate);
unbind_tstate(main_tstate);
/* This thread state may be bound/unbound repeatedly,
so we must erase evidence that it was ever bound (or unbound). */
main_tstate->_status.bound = 0;
main_tstate->_status.unbound = 0;
/* We must fully unlink the thread state from any OS thread,
to allow it to be bound more than once. */
main_tstate->thread_id = 0;
#ifdef PY_HAVE_THREAD_NATIVE_ID
main_tstate->native_thread_id = 0;
#endif
}
static inline void
acquire_global_objects_lock(_PyRuntimeState *runtime)
{
/* For now we can rely on the GIL, so we don't actually
acquire a global lock here. */
assert(current_fast_get(runtime) != NULL);
}
static inline void
release_global_objects_lock(_PyRuntimeState *runtime)
{
/* For now we can rely on the GIL, so we don't actually
release a global lock here. */
assert(current_fast_get(runtime) != NULL);
}
PyObject *
_Py_AddToGlobalDict(PyObject *dict, PyObject *key, PyObject *value)
{
assert(dict != NULL);
assert(PyDict_CheckExact(dict));
/* All global objects are stored in _PyRuntime
and owned by the main interpreter. */
_PyRuntimeState *runtime = &_PyRuntime;
PyThreadState *curts = current_fast_get(runtime);
PyInterpreterState *interp = curts->interp;
assert(interp != NULL); // The GIL must be held.
/* Due to interpreter isolation we must hold a global lock,
starting at this point and ending before we return.
Note that the operations in this function are very fucused
and we should not expect any reentrancy. */
acquire_global_objects_lock(runtime);
/* Swap to the main interpreter, if necessary. */
PyThreadState *oldts = NULL;
if (!_Py_IsMainInterpreter(interp)) {
PyThreadState *main_tstate = bind_global_objects_state(runtime);
oldts = _PyThreadState_Swap(runtime, main_tstate);
assert(oldts != NULL);
assert(!_Py_IsMainInterpreter(oldts->interp));
/* The limitations of the global objects thread state apply
from this point to the point we swap back to oldts. */
}
/* This might trigger a resize, which is why we must "acquire"
the global object state. Also note that PyDict_SetDefault()
must be compatible with our reentrancy and global objects state
constraints. */
PyObject *actual = PyDict_SetDefault(dict, key, value);
if (actual == NULL) {
/* Raising an exception from one interpreter in another
is problematic, so we clear it and let the caller deal
with the returned NULL. */
assert(PyErr_ExceptionMatches(PyExc_MemoryError));
PyErr_Clear();
}
/* Swap back, it it wasn't in the main interpreter already. */
if (oldts != NULL) {
// The returned tstate should be _PyRuntime.cached_objects.main_tstate.
_PyThreadState_Swap(runtime, oldts);
unbind_global_objects_state(runtime);
}
release_global_objects_lock(runtime);
// XXX Immortalize the key and value.
return actual;
}
/*************************************/
/* the per-interpreter runtime state */
/*************************************/
@ -1217,8 +1335,7 @@ free_threadstate(PyThreadState *tstate)
static void
init_threadstate(PyThreadState *tstate,
PyInterpreterState *interp, uint64_t id,
PyThreadState *next)
PyInterpreterState *interp, uint64_t id)
{
if (tstate->_status.initialized) {
Py_FatalError("thread state already initialized");
@ -1227,18 +1344,13 @@ init_threadstate(PyThreadState *tstate,
assert(interp != NULL);
tstate->interp = interp;
// next/prev are set in add_threadstate().
assert(tstate->next == NULL);
assert(tstate->prev == NULL);
assert(id > 0);
tstate->id = id;
assert(interp->threads.head == tstate);
assert((next != NULL && id != 1) || (next == NULL && id == 1));
if (next != NULL) {
assert(next->prev == NULL || next->prev == tstate);
next->prev = tstate;
}
tstate->next = next;
assert(tstate->prev == NULL);
// thread_id and native_thread_id are set in bind_tstate().
tstate->py_recursion_limit = interp->ceval.recursion_limit,
@ -1259,6 +1371,22 @@ init_threadstate(PyThreadState *tstate,
tstate->_status.initialized = 1;
}
static void
add_threadstate(PyInterpreterState *interp, PyThreadState *tstate,
PyThreadState *next)
{
assert(interp->threads.head != tstate);
assert((next != NULL && tstate->id != 1) ||
(next == NULL && tstate->id == 1));
if (next != NULL) {
assert(next->prev == NULL || next->prev == tstate);
next->prev = tstate;
}
tstate->next = next;
assert(tstate->prev == NULL);
interp->threads.head = tstate;
}
static PyThreadState *
new_threadstate(PyInterpreterState *interp)
{
@ -1298,9 +1426,9 @@ new_threadstate(PyInterpreterState *interp)
&initial._main_interpreter._initial_thread,
sizeof(*tstate));
}
interp->threads.head = tstate;
init_threadstate(tstate, interp, id, old_head);
init_threadstate(tstate, interp, id);
add_threadstate(interp, tstate, old_head);
HEAD_UNLOCK(runtime);
if (!used_newtstate) {
@ -1347,6 +1475,33 @@ _PyThreadState_Init(PyThreadState *tstate)
Py_FatalError("_PyThreadState_Init() is for internal use only");
}
void
_PyThreadState_InitDetached(PyThreadState *tstate, PyInterpreterState *interp)
{
_PyRuntimeState *runtime = interp->runtime;
HEAD_LOCK(runtime);
interp->threads.next_unique_id += 1;
uint64_t id = interp->threads.next_unique_id;
HEAD_UNLOCK(runtime);
init_threadstate(tstate, interp, id);
// We do not call add_threadstate().
}
static void
clear_datastack(PyThreadState *tstate)
{
_PyStackChunk *chunk = tstate->datastack_chunk;
tstate->datastack_chunk = NULL;
while (chunk != NULL) {
_PyStackChunk *prev = chunk->previous;
_PyObject_VirtualFree(chunk, chunk->size);
chunk = prev;
}
}
void
PyThreadState_Clear(PyThreadState *tstate)
{
@ -1421,7 +1576,6 @@ PyThreadState_Clear(PyThreadState *tstate)
// XXX Do it as early in the function as possible.
}
/* Common code for PyThreadState_Delete() and PyThreadState_DeleteCurrent() */
static void
tstate_delete_common(PyThreadState *tstate)
@ -1454,17 +1608,25 @@ tstate_delete_common(PyThreadState *tstate)
unbind_tstate(tstate);
// XXX Move to PyThreadState_Clear()?
_PyStackChunk *chunk = tstate->datastack_chunk;
tstate->datastack_chunk = NULL;
while (chunk != NULL) {
_PyStackChunk *prev = chunk->previous;
_PyObject_VirtualFree(chunk, chunk->size);
chunk = prev;
}
clear_datastack(tstate);
tstate->_status.finalized = 1;
}
void
_PyThreadState_ClearDetached(PyThreadState *tstate)
{
assert(!tstate->_status.bound);
assert(!tstate->_status.bound_gilstate);
assert(tstate->datastack_chunk == NULL);
assert(tstate->thread_id == 0);
assert(tstate->native_thread_id == 0);
assert(tstate->next == NULL);
assert(tstate->prev == NULL);
PyThreadState_Clear(tstate);
clear_datastack(tstate);
}
static void
zapthreads(PyInterpreterState *interp)