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bpo-39984: Move pending calls to PyInterpreterState (GH-19066)

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If Py_AddPendingCall() is called in a subinterpreter, the function is
now scheduled to be called from the subinterpreter, rather than being
called from the main interpreter.

Each subinterpreter now has its own list of scheduled calls.

* Move pending and eval_breaker fields from _PyRuntimeState.ceval
  to PyInterpreterState.ceval.
* new_interpreter() now calls _PyEval_InitThreads() to create
  pending calls lock.
* Fix Py_AddPendingCall() for subinterpreters. It now calls
  _PyThreadState_GET() which works in a subinterpreter if the
  caller holds the GIL, and only falls back on
  PyGILState_GetThisThreadState() if _PyThreadState_GET()
  returns NULL.
This commit is contained in:
Victor Stinner 2020-03-19 02:41:21 +01:00 committed by GitHub
parent 3cde88439d
commit 50e6e99178
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
8 changed files with 128 additions and 83 deletions
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10
Doc/c-api/init.rst
View file

@ -1389,6 +1389,10 @@ pointer and a void pointer argument.
This function doesn't need a current thread state to run, and it doesn't
need the global interpreter lock.
To call this function in a subinterpreter, the caller must hold the GIL.
Otherwise, the function *func* can be scheduled to be called from the wrong
interpreter.
.. warning::
This is a low-level function, only useful for very special cases.
There is no guarantee that *func* will be called as quick as
@ -1397,6 +1401,12 @@ pointer and a void pointer argument.
function is generally **not** suitable for calling Python code from
arbitrary C threads. Instead, use the :ref:`PyGILState API<gilstate>`.
.. versionchanged:: 3.9
If this function is called in a subinterpreter, the function *func* is
now scheduled to be called from the subinterpreter, rather than being
called from the main interpreter. Each subinterpreter now has its own
list of scheduled calls.
.. versionadded:: 3.1
.. _profiling:

6
Doc/whatsnew/3.9.rst
View file

@ -514,6 +514,12 @@ Build and C API Changes
Extension modules without module state (``m_size <= 0``) are not affected.
* If :c:func:`Py_AddPendingCall` is called in a subinterpreter, the function is
now scheduled to be called from the subinterpreter, rather than being called
from the main interpreter. Each subinterpreter now has its own list of
scheduled calls.
(Contributed by Victor Stinner in :issue:`39984`.)
Deprecated
==========

8
Include/internal/pycore_pystate.h
View file

@ -35,12 +35,8 @@ struct _pending_calls {
struct _ceval_runtime_state {
int recursion_limit;
/* This single variable consolidates all requests to break out of
the fast path in the eval loop. */
_Py_atomic_int eval_breaker;
/* Request for dropping the GIL */
_Py_atomic_int gil_drop_request;
struct _pending_calls pending;
/* Request for checking signals. */
_Py_atomic_int signals_pending;
struct _gil_runtime_state gil;
@ -53,6 +49,10 @@ struct _ceval_state {
c_tracefunc. This speeds up the if statement in
_PyEval_EvalFrameDefault() after fast_next_opcode. */
int tracing_possible;
/* This single variable consolidates all requests to break out of
the fast path in the eval loop. */
_Py_atomic_int eval_breaker;
struct _pending_calls pending;
};
/* interpreter state */

4
Misc/NEWS.d/next/Core and Builtins/2020-03-19-00-45-37.bpo-39984.u-bHIq.rst Normal file
View file

@ -0,0 +1,4 @@
If :c:func:`Py_AddPendingCall` is called in a subinterpreter, the function is
now scheduled to be called from the subinterpreter, rather than being called
from the main interpreter. Each subinterpreter now has its own list of
scheduled calls.

4
Modules/signalmodule.c
View file

@ -304,7 +304,7 @@ trip_signal(int sig_num)
if (wakeup.warn_on_full_buffer ||
last_error != WSAEWOULDBLOCK)
{
/* Py_AddPendingCall() isn't signal-safe, but we
/* _PyEval_AddPendingCall() isn't signal-safe, but we
still use it for this exceptional case. */
_PyEval_AddPendingCall(tstate,
report_wakeup_send_error,
@ -323,7 +323,7 @@ trip_signal(int sig_num)
if (wakeup.warn_on_full_buffer ||
(errno != EWOULDBLOCK && errno != EAGAIN))
{
/* Py_AddPendingCall() isn't signal-safe, but we
/* _PyEval_AddPendingCall() isn't signal-safe, but we
still use it for this exceptional case. */
_PyEval_AddPendingCall(tstate,
report_wakeup_write_error,

161
Python/ceval.c
View file

@ -120,66 +120,64 @@ static size_t opcache_global_hits = 0;
static size_t opcache_global_misses = 0;
#endif
#define GIL_REQUEST _Py_atomic_load_relaxed(&ceval->gil_drop_request)
/* This can set eval_breaker to 0 even though gil_drop_request became
1. We believe this is all right because the eval loop will release
the GIL eventually anyway. */
#define COMPUTE_EVAL_BREAKER(ceval) \
#define COMPUTE_EVAL_BREAKER(ceval, ceval2) \
_Py_atomic_store_relaxed( \
&(ceval)->eval_breaker, \
GIL_REQUEST | \
&(ceval2)->eval_breaker, \
_Py_atomic_load_relaxed(&(ceval)->gil_drop_request) | \
_Py_atomic_load_relaxed(&(ceval)->signals_pending) | \
_Py_atomic_load_relaxed(&(ceval)->pending.calls_to_do) | \
(ceval)->pending.async_exc)
_Py_atomic_load_relaxed(&(ceval2)->pending.calls_to_do) | \
(ceval2)->pending.async_exc)
#define SET_GIL_DROP_REQUEST(ceval) \
do { \
_Py_atomic_store_relaxed(&(ceval)->gil_drop_request, 1); \
_Py_atomic_store_relaxed(&(ceval)->eval_breaker, 1); \
_Py_atomic_store_relaxed(&(ceval2)->eval_breaker, 1); \
} while (0)
#define RESET_GIL_DROP_REQUEST(ceval) \
#define RESET_GIL_DROP_REQUEST(ceval, ceval2) \
do { \
_Py_atomic_store_relaxed(&(ceval)->gil_drop_request, 0); \
COMPUTE_EVAL_BREAKER(ceval); \
COMPUTE_EVAL_BREAKER(ceval, ceval2); \
} while (0)
/* Pending calls are only modified under pending_lock */
#define SIGNAL_PENDING_CALLS(ceval) \
#define SIGNAL_PENDING_CALLS(ceval2) \
do { \
_Py_atomic_store_relaxed(&(ceval)->pending.calls_to_do, 1); \
_Py_atomic_store_relaxed(&(ceval)->eval_breaker, 1); \
_Py_atomic_store_relaxed(&(ceval2)->pending.calls_to_do, 1); \
_Py_atomic_store_relaxed(&(ceval2)->eval_breaker, 1); \
} while (0)
#define UNSIGNAL_PENDING_CALLS(ceval) \
#define UNSIGNAL_PENDING_CALLS(ceval, ceval2) \
do { \
_Py_atomic_store_relaxed(&(ceval)->pending.calls_to_do, 0); \
COMPUTE_EVAL_BREAKER(ceval); \
_Py_atomic_store_relaxed(&(ceval2)->pending.calls_to_do, 0); \
COMPUTE_EVAL_BREAKER(ceval, ceval2); \
} while (0)
#define SIGNAL_PENDING_SIGNALS(ceval) \
#define SIGNAL_PENDING_SIGNALS(ceval, ceval2) \
do { \
_Py_atomic_store_relaxed(&(ceval)->signals_pending, 1); \
_Py_atomic_store_relaxed(&(ceval)->eval_breaker, 1); \
_Py_atomic_store_relaxed(&(ceval2)->eval_breaker, 1); \
} while (0)
#define UNSIGNAL_PENDING_SIGNALS(ceval) \
#define UNSIGNAL_PENDING_SIGNALS(ceval, ceval2) \
do { \
_Py_atomic_store_relaxed(&(ceval)->signals_pending, 0); \
COMPUTE_EVAL_BREAKER(ceval); \
COMPUTE_EVAL_BREAKER(ceval, ceval2); \
} while (0)
#define SIGNAL_ASYNC_EXC(ceval) \
#define SIGNAL_ASYNC_EXC(ceval2) \
do { \
(ceval)->pending.async_exc = 1; \
_Py_atomic_store_relaxed(&(ceval)->eval_breaker, 1); \
(ceval2)->pending.async_exc = 1; \
_Py_atomic_store_relaxed(&(ceval2)->eval_breaker, 1); \
} while (0)
#define UNSIGNAL_ASYNC_EXC(ceval) \
#define UNSIGNAL_ASYNC_EXC(ceval, ceval2) \
do { \
(ceval)->pending.async_exc = 0; \
COMPUTE_EVAL_BREAKER(ceval); \
(ceval2)->pending.async_exc = 0; \
COMPUTE_EVAL_BREAKER(ceval, ceval2); \
} while (0)
@ -215,22 +213,21 @@ PyEval_ThreadsInitialized(void)
PyStatus
_PyEval_InitThreads(PyThreadState *tstate)
{
if (tstate == NULL) {
return _PyStatus_ERR("tstate is NULL");
assert(tstate != NULL);
if (_Py_IsMainInterpreter(tstate)) {
struct _gil_runtime_state *gil = &tstate->interp->runtime->ceval.gil;
if (gil_created(gil)) {
return _PyStatus_OK();
}
PyThread_init_thread();
create_gil(gil);
take_gil(tstate);
}
struct _ceval_runtime_state *ceval = &tstate->interp->runtime->ceval;
struct _gil_runtime_state *gil = &ceval->gil;
if (gil_created(gil)) {
return _PyStatus_OK();
}
PyThread_init_thread();
create_gil(gil);
take_gil(tstate);
struct _pending_calls *pending = &ceval->pending;
struct _pending_calls *pending = &tstate->interp->ceval.pending;
assert(pending->lock == NULL);
pending->lock = PyThread_allocate_lock();
if (pending->lock == NULL) {
return _PyStatus_NO_MEMORY();
@ -248,8 +245,7 @@ PyEval_InitThreads(void)
void
_PyEval_FiniThreads(PyThreadState *tstate)
{
struct _ceval_runtime_state *ceval = &tstate->interp->runtime->ceval;
struct _gil_runtime_state *gil = &ceval->gil;
struct _gil_runtime_state *gil = &tstate->interp->runtime->ceval.gil;
if (!gil_created(gil)) {
return;
}
@ -257,7 +253,7 @@ _PyEval_FiniThreads(PyThreadState *tstate)
destroy_gil(gil);
assert(!gil_created(gil));
struct _pending_calls *pending = &ceval->pending;
struct _pending_calls *pending = &tstate->interp->ceval.pending;
if (pending->lock != NULL) {
PyThread_free_lock(pending->lock);
pending->lock = NULL;
@ -308,18 +304,20 @@ PyEval_ReleaseLock(void)
{
_PyRuntimeState *runtime = &_PyRuntime;
PyThreadState *tstate = _PyRuntimeState_GetThreadState(runtime);
struct _ceval_state *ceval2 = &tstate->interp->ceval;
/* This function must succeed when the current thread state is NULL.
We therefore avoid PyThreadState_Get() which dumps a fatal error
in debug mode.
*/
drop_gil(&runtime->ceval, tstate);
drop_gil(&runtime->ceval, ceval2, tstate);
}
void
_PyEval_ReleaseLock(PyThreadState *tstate)
{
struct _ceval_runtime_state *ceval = &tstate->interp->runtime->ceval;
drop_gil(ceval, tstate);
struct _ceval_state *ceval2 = &tstate->interp->ceval;
drop_gil(ceval, ceval2, tstate);
}
void
@ -345,7 +343,8 @@ PyEval_ReleaseThread(PyThreadState *tstate)
if (new_tstate != tstate) {
Py_FatalError("wrong thread state");
}
drop_gil(&runtime->ceval, tstate);
struct _ceval_state *ceval2 = &tstate->interp->ceval;
drop_gil(&runtime->ceval, ceval2, tstate);
}
/* This function is called from PyOS_AfterFork_Child to destroy all threads
@ -356,7 +355,6 @@ PyEval_ReleaseThread(PyThreadState *tstate)
void
_PyEval_ReInitThreads(_PyRuntimeState *runtime)
{
struct _ceval_runtime_state *ceval = &runtime->ceval;
struct _gil_runtime_state *gil = &runtime->ceval.gil;
if (!gil_created(gil)) {
return;
@ -367,7 +365,7 @@ _PyEval_ReInitThreads(_PyRuntimeState *runtime)
take_gil(tstate);
struct _pending_calls *pending = &ceval->pending;
struct _pending_calls *pending = &tstate->interp->ceval.pending;
pending->lock = PyThread_allocate_lock();
if (pending->lock == NULL) {
Py_FatalError("Can't initialize threads for pending calls");
@ -383,8 +381,8 @@ _PyEval_ReInitThreads(_PyRuntimeState *runtime)
void
_PyEval_SignalAsyncExc(PyThreadState *tstate)
{
struct _ceval_runtime_state *ceval = &tstate->interp->runtime->ceval;
SIGNAL_ASYNC_EXC(ceval);
struct _ceval_state *ceval2 = &tstate->interp->ceval;
SIGNAL_ASYNC_EXC(ceval2);
}
PyThreadState *
@ -397,7 +395,8 @@ PyEval_SaveThread(void)
Py_FatalError("NULL tstate");
}
assert(gil_created(&ceval->gil));
drop_gil(ceval, tstate);
struct _ceval_state *ceval2 = &tstate->interp->ceval;
drop_gil(ceval, ceval2, tstate);
return tstate;
}
@ -439,10 +438,11 @@ void
_PyEval_SignalReceived(PyThreadState *tstate)
{
struct _ceval_runtime_state *ceval = &tstate->interp->runtime->ceval;
struct _ceval_state *ceval2 = &tstate->interp->ceval;
/* bpo-30703: Function called when the C signal handler of Python gets a
signal. We cannot queue a callback using Py_AddPendingCall() since
signal. We cannot queue a callback using _PyEval_AddPendingCall() since
that function is not async-signal-safe. */
SIGNAL_PENDING_SIGNALS(ceval);
SIGNAL_PENDING_SIGNALS(ceval, ceval2);
}
/* Push one item onto the queue while holding the lock. */
@ -485,8 +485,8 @@ int
_PyEval_AddPendingCall(PyThreadState *tstate,
int (*func)(void *), void *arg)
{
struct _ceval_runtime_state *ceval = &tstate->interp->runtime->ceval;
struct _pending_calls *pending = &ceval->pending;
struct _ceval_state *ceval2 = &tstate->interp->ceval;
struct _pending_calls *pending = &ceval2->pending;
PyThread_acquire_lock(pending->lock, WAIT_LOCK);
if (pending->finishing) {
@ -495,8 +495,8 @@ _PyEval_AddPendingCall(PyThreadState *tstate,
PyObject *exc, *val, *tb;
_PyErr_Fetch(tstate, &exc, &val, &tb);
_PyErr_SetString(tstate, PyExc_SystemError,
"Py_AddPendingCall: cannot add pending calls "
"(Python shutting down)");
"Py_AddPendingCall: cannot add pending calls "
"(Python shutting down)");
_PyErr_Print(tstate);
_PyErr_Restore(tstate, exc, val, tb);
return -1;
@ -505,18 +505,33 @@ _PyEval_AddPendingCall(PyThreadState *tstate,
PyThread_release_lock(pending->lock);
/* signal main loop */
SIGNAL_PENDING_CALLS(ceval);
SIGNAL_PENDING_CALLS(ceval2);
return result;
}
int
Py_AddPendingCall(int (*func)(void *), void *arg)
{
/* Get the Python thread state using PyGILState API, since
_PyThreadState_GET() returns NULL if the GIL is released.
/* Best-effort to support subinterpreters and calls with the GIL released.
First attempt _PyThreadState_GET() since it supports subinterpreters.
If the GIL is released, _PyThreadState_GET() returns NULL . In this
case, use PyGILState_GetThisThreadState() which works even if the GIL
is released.
Sadly, PyGILState_GetThisThreadState() doesn't support subinterpreters:
see bpo-10915 and bpo-15751.
Py_AddPendingCall() doesn't require the caller to hold the GIL. */
PyThreadState *tstate = PyGILState_GetThisThreadState();
assert(tstate != NULL);
PyThreadState *tstate = _PyThreadState_GET();
if (tstate == NULL) {
tstate = PyGILState_GetThisThreadState();
}
/* tstate can be NULL if Py_AddPendingCall() is called in a thread
which is no Python thread state. Fail with a fatal error in this
case. */
ensure_tstate_not_null(__func__, tstate);
return _PyEval_AddPendingCall(tstate, func, arg);
}
@ -539,9 +554,10 @@ handle_signals(PyThreadState *tstate)
}
struct _ceval_runtime_state *ceval = &runtime->ceval;
UNSIGNAL_PENDING_SIGNALS(ceval);
struct _ceval_state *ceval2 = &interp->ceval;
UNSIGNAL_PENDING_SIGNALS(ceval, ceval2);
if (_PyErr_CheckSignals() < 0) {
SIGNAL_PENDING_SIGNALS(ceval); /* We're not done yet */
SIGNAL_PENDING_SIGNALS(ceval, ceval2); /* We're not done yet */
return -1;
}
return 0;
@ -553,6 +569,7 @@ make_pending_calls(PyThreadState *tstate)
static int busy = 0;
_PyRuntimeState *runtime = tstate->interp->runtime;
struct _ceval_state * ceval2 = &tstate->interp->ceval;
/* only service pending calls on main thread */
if (PyThread_get_thread_ident() != runtime->main_thread) {
@ -567,11 +584,11 @@ make_pending_calls(PyThreadState *tstate)
struct _ceval_runtime_state *ceval = &runtime->ceval;
/* unsignal before starting to call callbacks, so that any callback
added in-between re-signals */
UNSIGNAL_PENDING_CALLS(ceval);
UNSIGNAL_PENDING_CALLS(ceval, ceval2);
int res = 0;
/* perform a bounded number of calls, in case of recursion */
struct _pending_calls *pending = &ceval->pending;
struct _pending_calls *pending = &ceval2->pending;
for (int i=0; i<NPENDINGCALLS; i++) {
int (*func)(void *) = NULL;
void *arg = NULL;
@ -596,7 +613,7 @@ make_pending_calls(PyThreadState *tstate)
error:
busy = 0;
SIGNAL_PENDING_CALLS(ceval);
SIGNAL_PENDING_CALLS(ceval2);
return res;
}
@ -605,7 +622,7 @@ _Py_FinishPendingCalls(PyThreadState *tstate)
{
assert(PyGILState_Check());
struct _pending_calls *pending = &tstate->interp->runtime->ceval.pending;
struct _pending_calls *pending = &tstate->interp->ceval.pending;
PyThread_acquire_lock(pending->lock, WAIT_LOCK);
pending->finishing = 1;
@ -779,7 +796,7 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, PyFrameObject *f, int throwflag)
_PyRuntimeState * const runtime = &_PyRuntime;
struct _ceval_runtime_state * const ceval = &runtime->ceval;
struct _ceval_state * const ceval2 = &tstate->interp->ceval;
_Py_atomic_int * const eval_breaker = &ceval->eval_breaker;
_Py_atomic_int * const eval_breaker = &ceval2->eval_breaker;
PyCodeObject *co;
/* when tracing we set things up so that
@ -1254,7 +1271,7 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, PyFrameObject *f, int throwflag)
goto error;
}
}
if (_Py_atomic_load_relaxed(&ceval->pending.calls_to_do)) {
if (_Py_atomic_load_relaxed(&ceval2->pending.calls_to_do)) {
if (make_pending_calls(tstate) != 0) {
goto error;
}
@ -1265,7 +1282,7 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, PyFrameObject *f, int throwflag)
if (_PyThreadState_Swap(&runtime->gilstate, NULL) != tstate) {
Py_FatalError("tstate mix-up");
}
drop_gil(ceval, tstate);
drop_gil(ceval, ceval2, tstate);
/* Other threads may run now */
@ -1279,7 +1296,7 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, PyFrameObject *f, int throwflag)
if (tstate->async_exc != NULL) {
PyObject *exc = tstate->async_exc;
tstate->async_exc = NULL;
UNSIGNAL_ASYNC_EXC(ceval);
UNSIGNAL_ASYNC_EXC(ceval, ceval2);
_PyErr_SetNone(tstate, exc);
Py_DECREF(exc);
goto error;

10
Python/ceval_gil.h
View file

@ -141,7 +141,8 @@ static void recreate_gil(struct _gil_runtime_state *gil)
}
static void
drop_gil(struct _ceval_runtime_state *ceval, PyThreadState *tstate)
drop_gil(struct _ceval_runtime_state *ceval, struct _ceval_state *ceval2,
PyThreadState *tstate)
{
struct _gil_runtime_state *gil = &ceval->gil;
if (!_Py_atomic_load_relaxed(&gil->locked)) {
@ -168,7 +169,7 @@ drop_gil(struct _ceval_runtime_state *ceval, PyThreadState *tstate)
/* Not switched yet => wait */
if (((PyThreadState*)_Py_atomic_load_relaxed(&gil->last_holder)) == tstate)
{
RESET_GIL_DROP_REQUEST(ceval);
RESET_GIL_DROP_REQUEST(ceval, ceval2);
/* NOTE: if COND_WAIT does not atomically start waiting when
releasing the mutex, another thread can run through, take
the GIL and drop it again, and reset the condition
@ -230,6 +231,7 @@ take_gil(PyThreadState *tstate)
struct _ceval_runtime_state *ceval = &tstate->interp->runtime->ceval;
struct _gil_runtime_state *gil = &ceval->gil;
struct _ceval_state *ceval2 = &tstate->interp->ceval;
/* Check that _PyEval_InitThreads() was called to create the lock */
assert(gil_created(gil));
@ -279,7 +281,7 @@ take_gil(PyThreadState *tstate)
MUTEX_UNLOCK(gil->switch_mutex);
#endif
if (_Py_atomic_load_relaxed(&ceval->gil_drop_request)) {
RESET_GIL_DROP_REQUEST(ceval);
RESET_GIL_DROP_REQUEST(ceval, ceval2);
}
int must_exit = tstate_must_exit(tstate);
@ -299,7 +301,7 @@ take_gil(PyThreadState *tstate)
This code path can be reached by a daemon thread which was waiting
in take_gil() while the main thread called
wait_for_thread_shutdown() from Py_Finalize(). */
drop_gil(ceval, tstate);
drop_gil(ceval, ceval2, tstate);
PyThread_exit_thread();
}

8
Python/pylifecycle.c
View file

@ -556,7 +556,7 @@ pycore_create_interpreter(_PyRuntimeState *runtime,
return status;
}
/* Create the GIL */
/* Create the GIL and the pending calls lock */
status = _PyEval_InitThreads(tstate);
if (_PyStatus_EXCEPTION(status)) {
return status;
@ -1581,6 +1581,12 @@ new_interpreter(PyThreadState **tstate_p)
goto error;
}
/* Create the pending calls lock */
status = _PyEval_InitThreads(tstate);
if (_PyStatus_EXCEPTION(status)) {
return status;
}
*tstate_p = tstate;
return _PyStatus_OK();