diff --git a/Misc/NEWS.d/next/Core and Builtins/2024-01-17-00-52-57.gh-issue-113884.CvEjUE.rst b/Misc/NEWS.d/next/Core and Builtins/2024-01-17-00-52-57.gh-issue-113884.CvEjUE.rst new file mode 100644 index 00000000000..6a39fd2f60a --- /dev/null +++ b/Misc/NEWS.d/next/Core and Builtins/2024-01-17-00-52-57.gh-issue-113884.CvEjUE.rst @@ -0,0 +1 @@ +Make :class:`queue.SimpleQueue` thread safe when the GIL is disabled. diff --git a/Modules/_queuemodule.c b/Modules/_queuemodule.c index 8fca3cdd0de..18b24855c52 100644 --- a/Modules/_queuemodule.c +++ b/Modules/_queuemodule.c @@ -3,8 +3,9 @@ #endif #include "Python.h" -#include "pycore_ceval.h" // _PyEval_MakePendingCalls() +#include "pycore_ceval.h" // Py_MakePendingCalls() #include "pycore_moduleobject.h" // _PyModule_GetState() +#include "pycore_parking_lot.h" #include "pycore_time.h" // _PyTime_t #include @@ -151,7 +152,9 @@ RingBuf_Get(RingBuf *buf) return item; } -// Returns 0 on success or -1 if the buffer failed to grow +// Returns 0 on success or -1 if the buffer failed to grow. +// +// Steals a reference to item. static int RingBuf_Put(RingBuf *buf, PyObject *item) { @@ -164,7 +167,7 @@ RingBuf_Put(RingBuf *buf, PyObject *item) return -1; } } - buf->items[buf->put_idx] = Py_NewRef(item); + buf->items[buf->put_idx] = item; buf->put_idx = (buf->put_idx + 1) % buf->items_cap; buf->num_items++; return 0; @@ -184,9 +187,13 @@ RingBuf_IsEmpty(RingBuf *buf) typedef struct { PyObject_HEAD - PyThread_type_lock lock; - int locked; + + // Are there threads waiting for items + bool has_threads_waiting; + + // Items in the queue RingBuf buf; + PyObject *weakreflist; } simplequeueobject; @@ -209,12 +216,6 @@ simplequeue_dealloc(simplequeueobject *self) PyTypeObject *tp = Py_TYPE(self); PyObject_GC_UnTrack(self); - if (self->lock != NULL) { - /* Unlock the lock so it's safe to free it */ - if (self->locked > 0) - PyThread_release_lock(self->lock); - PyThread_free_lock(self->lock); - } (void)simplequeue_clear(self); if (self->weakreflist != NULL) PyObject_ClearWeakRefs((PyObject *) self); @@ -249,12 +250,6 @@ simplequeue_new_impl(PyTypeObject *type) self = (simplequeueobject *) type->tp_alloc(type, 0); if (self != NULL) { self->weakreflist = NULL; - self->lock = PyThread_allocate_lock(); - if (self->lock == NULL) { - Py_DECREF(self); - PyErr_SetString(PyExc_MemoryError, "can't allocate lock"); - return NULL; - } if (RingBuf_Init(&self->buf) < 0) { Py_DECREF(self); return NULL; @@ -264,7 +259,29 @@ simplequeue_new_impl(PyTypeObject *type) return (PyObject *) self; } +typedef struct { + bool handed_off; + simplequeueobject *queue; + PyObject *item; +} HandoffData; + +static void +maybe_handoff_item(HandoffData *data, PyObject **item, int has_more_waiters) +{ + if (item == NULL) { + // No threads were waiting + data->handed_off = false; + } + else { + // There was at least one waiting thread, hand off the item + *item = data->item; + data->handed_off = true; + } + data->queue->has_threads_waiting = has_more_waiters; +} + /*[clinic input] +@critical_section _queue.SimpleQueue.put item: object block: bool = True @@ -280,21 +297,28 @@ never blocks. They are provided for compatibility with the Queue class. static PyObject * _queue_SimpleQueue_put_impl(simplequeueobject *self, PyObject *item, int block, PyObject *timeout) -/*[clinic end generated code: output=4333136e88f90d8b input=6e601fa707a782d5]*/ +/*[clinic end generated code: output=4333136e88f90d8b input=a16dbb33363c0fa8]*/ { - /* BEGIN GIL-protected critical section */ - if (RingBuf_Put(&self->buf, item) < 0) - return NULL; - if (self->locked) { - /* A get() may be waiting, wake it up */ - self->locked = 0; - PyThread_release_lock(self->lock); + HandoffData data = { + .handed_off = 0, + .item = Py_NewRef(item), + .queue = self, + }; + if (self->has_threads_waiting) { + // Try to hand the item off directly if there are threads waiting + _PyParkingLot_Unpark(&self->has_threads_waiting, + (_Py_unpark_fn_t *)maybe_handoff_item, &data); + } + if (!data.handed_off) { + if (RingBuf_Put(&self->buf, item) < 0) { + return NULL; + } } - /* END GIL-protected critical section */ Py_RETURN_NONE; } /*[clinic input] +@critical_section _queue.SimpleQueue.put_nowait item: object @@ -307,12 +331,23 @@ for compatibility with the Queue class. static PyObject * _queue_SimpleQueue_put_nowait_impl(simplequeueobject *self, PyObject *item) -/*[clinic end generated code: output=0990536715efb1f1 input=36b1ea96756b2ece]*/ +/*[clinic end generated code: output=0990536715efb1f1 input=ce949cc2cd8a4119]*/ { return _queue_SimpleQueue_put_impl(self, item, 0, Py_None); } +static PyObject * +empty_error(PyTypeObject *cls) +{ + PyObject *module = PyType_GetModule(cls); + assert(module != NULL); + simplequeue_state *state = simplequeue_get_state(module); + PyErr_SetNone(state->EmptyError); + return NULL; +} + /*[clinic input] +@critical_section _queue.SimpleQueue.get cls: defining_class @@ -335,23 +370,15 @@ in that case). static PyObject * _queue_SimpleQueue_get_impl(simplequeueobject *self, PyTypeObject *cls, int block, PyObject *timeout_obj) -/*[clinic end generated code: output=5c2cca914cd1e55b input=5b4047bfbc645ec1]*/ +/*[clinic end generated code: output=5c2cca914cd1e55b input=f7836c65e5839c51]*/ { _PyTime_t endtime = 0; - _PyTime_t timeout; - PyObject *item; - PyLockStatus r; - PY_TIMEOUT_T microseconds; - PyThreadState *tstate = PyThreadState_Get(); // XXX Use PyThread_ParseTimeoutArg(). - if (block == 0) { - /* Non-blocking */ - microseconds = 0; - } - else if (timeout_obj != Py_None) { + if (block != 0 && !Py_IsNone(timeout_obj)) { /* With timeout */ + _PyTime_t timeout; if (_PyTime_FromSecondsObject(&timeout, timeout_obj, _PyTime_ROUND_CEILING) < 0) { return NULL; @@ -361,65 +388,64 @@ _queue_SimpleQueue_get_impl(simplequeueobject *self, PyTypeObject *cls, "'timeout' must be a non-negative number"); return NULL; } - microseconds = _PyTime_AsMicroseconds(timeout, - _PyTime_ROUND_CEILING); - if (microseconds > PY_TIMEOUT_MAX) { - PyErr_SetString(PyExc_OverflowError, - "timeout value is too large"); - return NULL; - } endtime = _PyDeadline_Init(timeout); } - else { - /* Infinitely blocking */ - microseconds = -1; - } - /* put() signals the queue to be non-empty by releasing the lock. - * So we simply try to acquire the lock in a loop, until the condition - * (queue non-empty) becomes true. - */ - while (RingBuf_IsEmpty(&self->buf)) { - /* First a simple non-blocking try without releasing the GIL */ - r = PyThread_acquire_lock_timed(self->lock, 0, 0); - if (r == PY_LOCK_FAILURE && microseconds != 0) { - Py_BEGIN_ALLOW_THREADS - r = PyThread_acquire_lock_timed(self->lock, microseconds, 1); - Py_END_ALLOW_THREADS + for (;;) { + if (!RingBuf_IsEmpty(&self->buf)) { + return RingBuf_Get(&self->buf); } - if (r == PY_LOCK_INTR && _PyEval_MakePendingCalls(tstate) < 0) { - return NULL; + if (!block) { + return empty_error(cls); } - if (r == PY_LOCK_FAILURE) { - PyObject *module = PyType_GetModule(cls); - simplequeue_state *state = simplequeue_get_state(module); - /* Timed out */ - PyErr_SetNone(state->EmptyError); - return NULL; - } - self->locked = 1; - /* Adjust timeout for next iteration (if any) */ - if (microseconds > 0) { - timeout = _PyDeadline_Get(endtime); - microseconds = _PyTime_AsMicroseconds(timeout, - _PyTime_ROUND_CEILING); + int64_t timeout_ns = -1; + if (endtime != 0) { + timeout_ns = _PyDeadline_Get(endtime); + if (timeout_ns < 0) { + return empty_error(cls); + } + } + + bool waiting = 1; + self->has_threads_waiting = waiting; + + PyObject *item = NULL; + int st = _PyParkingLot_Park(&self->has_threads_waiting, &waiting, + sizeof(bool), timeout_ns, &item, + /* detach */ 1); + switch (st) { + case Py_PARK_OK: { + assert(item != NULL); + return item; + } + case Py_PARK_TIMEOUT: { + return empty_error(cls); + } + case Py_PARK_INTR: { + // Interrupted + if (Py_MakePendingCalls() < 0) { + return NULL; + } + break; + } + case Py_PARK_AGAIN: { + // This should be impossible with the current implementation of + // PyParkingLot, but would be possible if critical sections / + // the GIL were released before the thread was added to the + // internal thread queue in the parking lot. + break; + } + default: { + Py_UNREACHABLE(); + } } } - - /* BEGIN GIL-protected critical section */ - item = RingBuf_Get(&self->buf); - if (self->locked) { - PyThread_release_lock(self->lock); - self->locked = 0; - } - /* END GIL-protected critical section */ - - return item; } /*[clinic input] +@critical_section _queue.SimpleQueue.get_nowait cls: defining_class @@ -434,12 +460,13 @@ raise the Empty exception. static PyObject * _queue_SimpleQueue_get_nowait_impl(simplequeueobject *self, PyTypeObject *cls) -/*[clinic end generated code: output=620c58e2750f8b8a input=842f732bf04216d3]*/ +/*[clinic end generated code: output=620c58e2750f8b8a input=d48be63633fefae9]*/ { return _queue_SimpleQueue_get_impl(self, cls, 0, Py_None); } /*[clinic input] +@critical_section _queue.SimpleQueue.empty -> bool Return True if the queue is empty, False otherwise (not reliable!). @@ -447,12 +474,13 @@ Return True if the queue is empty, False otherwise (not reliable!). static int _queue_SimpleQueue_empty_impl(simplequeueobject *self) -/*[clinic end generated code: output=1a02a1b87c0ef838 input=1a98431c45fd66f9]*/ +/*[clinic end generated code: output=1a02a1b87c0ef838 input=96cb22df5a67d831]*/ { return RingBuf_IsEmpty(&self->buf); } /*[clinic input] +@critical_section _queue.SimpleQueue.qsize -> Py_ssize_t Return the approximate size of the queue (not reliable!). @@ -460,7 +488,7 @@ Return the approximate size of the queue (not reliable!). static Py_ssize_t _queue_SimpleQueue_qsize_impl(simplequeueobject *self) -/*[clinic end generated code: output=f9dcd9d0a90e121e input=7a74852b407868a1]*/ +/*[clinic end generated code: output=f9dcd9d0a90e121e input=e218623cb8c16a79]*/ { return RingBuf_Len(&self->buf); } diff --git a/Modules/clinic/_queuemodule.c.h b/Modules/clinic/_queuemodule.c.h index 8e2a430835e..b3b6b8e96c1 100644 --- a/Modules/clinic/_queuemodule.c.h +++ b/Modules/clinic/_queuemodule.c.h @@ -6,6 +6,7 @@ preserve # include "pycore_gc.h" // PyGC_Head # include "pycore_runtime.h" // _Py_ID() #endif +#include "pycore_critical_section.h"// Py_BEGIN_CRITICAL_SECTION() #include "pycore_modsupport.h" // _PyArg_NoKeywords() PyDoc_STRVAR(simplequeue_new__doc__, @@ -107,7 +108,9 @@ _queue_SimpleQueue_put(simplequeueobject *self, PyObject *const *args, Py_ssize_ } timeout = args[2]; skip_optional_pos: + Py_BEGIN_CRITICAL_SECTION(self); return_value = _queue_SimpleQueue_put_impl(self, item, block, timeout); + Py_END_CRITICAL_SECTION(); exit: return return_value; @@ -165,7 +168,9 @@ _queue_SimpleQueue_put_nowait(simplequeueobject *self, PyObject *const *args, Py goto exit; } item = args[0]; + Py_BEGIN_CRITICAL_SECTION(self); return_value = _queue_SimpleQueue_put_nowait_impl(self, item); + Py_END_CRITICAL_SECTION(); exit: return return_value; @@ -244,7 +249,9 @@ _queue_SimpleQueue_get(simplequeueobject *self, PyTypeObject *cls, PyObject *con } timeout_obj = args[1]; skip_optional_pos: + Py_BEGIN_CRITICAL_SECTION(self); return_value = _queue_SimpleQueue_get_impl(self, cls, block, timeout_obj); + Py_END_CRITICAL_SECTION(); exit: return return_value; @@ -269,11 +276,18 @@ _queue_SimpleQueue_get_nowait_impl(simplequeueobject *self, static PyObject * _queue_SimpleQueue_get_nowait(simplequeueobject *self, PyTypeObject *cls, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames) { + PyObject *return_value = NULL; + if (nargs) { PyErr_SetString(PyExc_TypeError, "get_nowait() takes no arguments"); - return NULL; + goto exit; } - return _queue_SimpleQueue_get_nowait_impl(self, cls); + Py_BEGIN_CRITICAL_SECTION(self); + return_value = _queue_SimpleQueue_get_nowait_impl(self, cls); + Py_END_CRITICAL_SECTION(); + +exit: + return return_value; } PyDoc_STRVAR(_queue_SimpleQueue_empty__doc__, @@ -294,7 +308,9 @@ _queue_SimpleQueue_empty(simplequeueobject *self, PyObject *Py_UNUSED(ignored)) PyObject *return_value = NULL; int _return_value; + Py_BEGIN_CRITICAL_SECTION(self); _return_value = _queue_SimpleQueue_empty_impl(self); + Py_END_CRITICAL_SECTION(); if ((_return_value == -1) && PyErr_Occurred()) { goto exit; } @@ -322,7 +338,9 @@ _queue_SimpleQueue_qsize(simplequeueobject *self, PyObject *Py_UNUSED(ignored)) PyObject *return_value = NULL; Py_ssize_t _return_value; + Py_BEGIN_CRITICAL_SECTION(self); _return_value = _queue_SimpleQueue_qsize_impl(self); + Py_END_CRITICAL_SECTION(); if ((_return_value == -1) && PyErr_Occurred()) { goto exit; } @@ -331,4 +349,4 @@ _queue_SimpleQueue_qsize(simplequeueobject *self, PyObject *Py_UNUSED(ignored)) exit: return return_value; } -/*[clinic end generated code: output=457310b20cb61cf8 input=a9049054013a1b77]*/ +/*[clinic end generated code: output=242950edc8f7dfd7 input=a9049054013a1b77]*/