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Strip down gil.h to the simple version only. #4218

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Strip down gil.h to the simple version only. #4218

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7bbc06e
Strip down gil.h to the simple version only.
Oct 6, 2022
e70b38b
Explicit `py::gil_scoped_release()` in test_interpreter.cpp `TEST_CAS…
Oct 6, 2022
7115159
clang-tidy fix
Oct 6, 2022
7fc5df8
Delete copy ctor, assignment operator also in `!defined(WITH_THREAD)`…
Oct 6, 2022
f12f194
Use the simplified gil.h from detail/internals.h (to replace gil_scop…
Oct 6, 2022
ad126f5
Remove explicit `get_internals()` from `TEST_CASE("Threads")` and `RE…
Oct 6, 2022
be83638
@jbms wrote: We can leave internals.tstate present (depending on ABI …
Oct 6, 2022
b6b3ad1
Correct silly mistake in previous commit. More version guards are nee…
Oct 6, 2022
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21 changes: 12 additions & 9 deletions include/pybind11/detail/internals.h
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@

#pragma once

#include "../gil.h"
#include "../pytypes.h"

#include <exception>
Expand Down Expand Up @@ -169,16 +170,21 @@ struct internals {
PyTypeObject *default_metaclass;
PyObject *instance_base;
#if defined(WITH_THREAD)
# if PYBIND11_INTERNALS_VERSION < 6
PYBIND11_TLS_KEY_INIT(tstate)
# endif // PYBIND11_INTERNALS_VERSION < 6
# if PYBIND11_INTERNALS_VERSION > 4
PYBIND11_TLS_KEY_INIT(loader_life_support_tls_key)
# endif // PYBIND11_INTERNALS_VERSION > 4
# if PYBIND11_INTERNALS_VERSION < 6
PyInterpreterState *istate = nullptr;
# endif // PYBIND11_INTERNALS_VERSION < 6
~internals() {
# if PYBIND11_INTERNALS_VERSION > 4
PYBIND11_TLS_FREE(loader_life_support_tls_key);
# endif // PYBIND11_INTERNALS_VERSION > 4

# if PYBIND11_INTERNALS_VERSION < 6
// This destructor is called *after* Py_Finalize() in finalize_interpreter().
// That *SHOULD BE* fine. The following details what happens when PyThread_tss_free is
// called. PYBIND11_TLS_FREE is PyThread_tss_free on python 3.7+. On older python, it does
Expand All @@ -187,6 +193,7 @@ struct internals {
// Neither of those have anything to do with CPython internals. PyMem_RawFree *requires*
// that the `tstate` be allocated with the CPython allocator.
PYBIND11_TLS_FREE(tstate);
# endif // PYBIND11_INTERNALS_VERSION < 6
}
#endif
};
Expand Down Expand Up @@ -408,15 +415,7 @@ PYBIND11_NOINLINE internals &get_internals() {
return **internals_pp;
}

// Ensure that the GIL is held since we will need to make Python calls.
// Cannot use py::gil_scoped_acquire here since that constructor calls get_internals.
struct gil_scoped_acquire_local {
gil_scoped_acquire_local() : state(PyGILState_Ensure()) {}
gil_scoped_acquire_local(const gil_scoped_acquire_local &) = delete;
gil_scoped_acquire_local &operator=(const gil_scoped_acquire_local &) = delete;
~gil_scoped_acquire_local() { PyGILState_Release(state); }
const PyGILState_STATE state;
} gil;
gil_scoped_acquire gil;
error_scope err_scope;

PYBIND11_STR_TYPE id(PYBIND11_INTERNALS_ID);
Expand Down Expand Up @@ -445,19 +444,23 @@ PYBIND11_NOINLINE internals &get_internals() {
# if PY_VERSION_HEX < 0x03090000
PyEval_InitThreads();
# endif
# if PYBIND11_INTERNALS_VERSION < 6
PyThreadState *tstate = PyThreadState_Get();
if (!PYBIND11_TLS_KEY_CREATE(internals_ptr->tstate)) {
pybind11_fail("get_internals: could not successfully initialize the tstate TSS key!");
}
PYBIND11_TLS_REPLACE_VALUE(internals_ptr->tstate, tstate);
# endif

# if PYBIND11_INTERNALS_VERSION > 4
if (!PYBIND11_TLS_KEY_CREATE(internals_ptr->loader_life_support_tls_key)) {
pybind11_fail("get_internals: could not successfully initialize the "
"loader_life_support TSS key!");
}
# endif
# if PYBIND11_INTERNALS_VERSION < 6
internals_ptr->istate = tstate->interp;
# endif
#endif
builtins[id] = capsule(internals_pp);
internals_ptr->registered_exception_translators.push_front(&translate_exception);
Expand Down
178 changes: 11 additions & 167 deletions include/pybind11/gil.h
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Original file line number Diff line number Diff line change
Expand Up @@ -10,180 +10,16 @@
#pragma once

#include "detail/common.h"
#include "detail/internals.h"

PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)

PYBIND11_NAMESPACE_BEGIN(detail)
#if defined(WITH_THREAD)

// forward declarations
PyThreadState *get_thread_state_unchecked();

PYBIND11_NAMESPACE_END(detail)

#if defined(WITH_THREAD) && !defined(PYPY_VERSION)

/* The functions below essentially reproduce the PyGILState_* API using a RAII
* pattern, but there are a few important differences:
*
* 1. When acquiring the GIL from an non-main thread during the finalization
* phase, the GILState API blindly terminates the calling thread, which
* is often not what is wanted. This API does not do this.
*
* 2. The gil_scoped_release function can optionally cut the relationship
* of a PyThreadState and its associated thread, which allows moving it to
* another thread (this is a fairly rare/advanced use case).
*
* 3. The reference count of an acquired thread state can be controlled. This
* can be handy to prevent cases where callbacks issued from an external
* thread would otherwise constantly construct and destroy thread state data
* structures.
*
* See the Python bindings of NanoGUI (http://github.com/wjakob/nanogui) for an
* example which uses features 2 and 3 to migrate the Python thread of
* execution to another thread (to run the event loop on the original thread,
* in this case).
*/

class gil_scoped_acquire {
public:
PYBIND11_NOINLINE gil_scoped_acquire() {
auto &internals = detail::get_internals();
tstate = (PyThreadState *) PYBIND11_TLS_GET_VALUE(internals.tstate);

if (!tstate) {
/* Check if the GIL was acquired using the PyGILState_* API instead (e.g. if
calling from a Python thread). Since we use a different key, this ensures
we don't create a new thread state and deadlock in PyEval_AcquireThread
below. Note we don't save this state with internals.tstate, since we don't
create it we would fail to clear it (its reference count should be > 0). */
tstate = PyGILState_GetThisThreadState();
}

if (!tstate) {
tstate = PyThreadState_New(internals.istate);
# if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
if (!tstate) {
pybind11_fail("scoped_acquire: could not create thread state!");
}
# endif
tstate->gilstate_counter = 0;
PYBIND11_TLS_REPLACE_VALUE(internals.tstate, tstate);
} else {
release = detail::get_thread_state_unchecked() != tstate;
}

if (release) {
PyEval_AcquireThread(tstate);
}

inc_ref();
}

gil_scoped_acquire(const gil_scoped_acquire &) = delete;
gil_scoped_acquire &operator=(const gil_scoped_acquire &) = delete;

void inc_ref() { ++tstate->gilstate_counter; }

PYBIND11_NOINLINE void dec_ref() {
--tstate->gilstate_counter;
# if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
if (detail::get_thread_state_unchecked() != tstate) {
pybind11_fail("scoped_acquire::dec_ref(): thread state must be current!");
}
if (tstate->gilstate_counter < 0) {
pybind11_fail("scoped_acquire::dec_ref(): reference count underflow!");
}
# endif
if (tstate->gilstate_counter == 0) {
# if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
if (!release) {
pybind11_fail("scoped_acquire::dec_ref(): internal error!");
}
# endif
PyThreadState_Clear(tstate);
if (active) {
PyThreadState_DeleteCurrent();
}
PYBIND11_TLS_DELETE_VALUE(detail::get_internals().tstate);
release = false;
}
}

/// This method will disable the PyThreadState_DeleteCurrent call and the
/// GIL won't be acquired. This method should be used if the interpreter
/// could be shutting down when this is called, as thread deletion is not
/// allowed during shutdown. Check _Py_IsFinalizing() on Python 3.7+, and
/// protect subsequent code.
PYBIND11_NOINLINE void disarm() { active = false; }

PYBIND11_NOINLINE ~gil_scoped_acquire() {
dec_ref();
if (release) {
PyEval_SaveThread();
}
}

private:
PyThreadState *tstate = nullptr;
bool release = true;
bool active = true;
};

class gil_scoped_release {
public:
explicit gil_scoped_release(bool disassoc = false) : disassoc(disassoc) {
// `get_internals()` must be called here unconditionally in order to initialize
// `internals.tstate` for subsequent `gil_scoped_acquire` calls. Otherwise, an
// initialization race could occur as multiple threads try `gil_scoped_acquire`.
auto &internals = detail::get_internals();
// NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
tstate = PyEval_SaveThread();
if (disassoc) {
// Python >= 3.7 can remove this, it's an int before 3.7
// NOLINTNEXTLINE(readability-qualified-auto)
auto key = internals.tstate;
PYBIND11_TLS_DELETE_VALUE(key);
}
}

gil_scoped_release(const gil_scoped_acquire &) = delete;
gil_scoped_release &operator=(const gil_scoped_acquire &) = delete;

/// This method will disable the PyThreadState_DeleteCurrent call and the
/// GIL won't be acquired. This method should be used if the interpreter
/// could be shutting down when this is called, as thread deletion is not
/// allowed during shutdown. Check _Py_IsFinalizing() on Python 3.7+, and
/// protect subsequent code.
PYBIND11_NOINLINE void disarm() { active = false; }

~gil_scoped_release() {
if (!tstate) {
return;
}
// `PyEval_RestoreThread()` should not be called if runtime is finalizing
if (active) {
PyEval_RestoreThread(tstate);
}
if (disassoc) {
// Python >= 3.7 can remove this, it's an int before 3.7
// NOLINTNEXTLINE(readability-qualified-auto)
auto key = detail::get_internals().tstate;
PYBIND11_TLS_REPLACE_VALUE(key, tstate);
}
}

private:
PyThreadState *tstate;
bool disassoc;
bool active = true;
};
#elif defined(PYPY_VERSION)
class gil_scoped_acquire {
PyGILState_STATE state;

public:
gil_scoped_acquire() { state = PyGILState_Ensure(); }
gil_scoped_acquire() : state{PyGILState_Ensure()} {}
gil_scoped_acquire(const gil_scoped_acquire &) = delete;
gil_scoped_acquire &operator=(const gil_scoped_acquire &) = delete;
~gil_scoped_acquire() { PyGILState_Release(state); }
Expand All @@ -194,19 +30,27 @@ class gil_scoped_release {
PyThreadState *state;

public:
gil_scoped_release() { state = PyEval_SaveThread(); }
gil_scoped_release() : state{PyEval_SaveThread()} {}
gil_scoped_release(const gil_scoped_release &) = delete;
gil_scoped_release &operator=(const gil_scoped_acquire &) = delete;
~gil_scoped_release() { PyEval_RestoreThread(state); }
void disarm() {}
};

#else

class gil_scoped_acquire {
gil_scoped_acquire(const gil_scoped_acquire &) = delete;
gil_scoped_acquire &operator=(const gil_scoped_acquire &) = delete;
void disarm() {}
};

class gil_scoped_release {
gil_scoped_release(const gil_scoped_release &) = delete;
gil_scoped_release &operator=(const gil_scoped_acquire &) = delete;
void disarm() {}
};

#endif

PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
1 change: 0 additions & 1 deletion tests/test_embed/test_interpreter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -293,7 +293,6 @@ TEST_CASE("Threads") {

{
py::gil_scoped_release gil_release{};
REQUIRE(has_pybind11_internals_static());

auto threads = std::vector<std::thread>();
for (auto i = 0; i < num_threads; ++i) {
Expand Down