The PyMutex implementation supports unlocking after fork because we
clear the list of waiters in parking_lot.c. This doesn't work as well
for _PyRecursiveMutex because on some systems, such as SerenityOS, the
thread id is not preserved across fork().
This adds a `_PyRecursiveMutex` type based on `PyMutex` and uses that
for the import lock. This fixes some data races in the free-threaded
build and generally simplifies the import lock code.
Add the ability to enable/disable the GIL at runtime, and use that in
the C module loading code.
We can't know before running a module init function if it supports
free-threading, so the GIL is temporarily enabled before doing so. If
the module declares support for running without the GIL, the GIL is
later disabled. Otherwise, the GIL is permanently enabled, and will
never be disabled again for the life of the current interpreter.
Basically, I've turned most of _PyImport_LoadDynamicModuleWithSpec() into two new functions (_PyImport_GetModInitFunc() and _PyImport_RunModInitFunc()) and moved the rest of it out into _imp_create_dynamic_impl(). There shouldn't be any changes in behavior.
This change makes some future changes simpler. This is particularly relevant to potentially calling each module init function in the main interpreter first. Thus the critical part of the PR is the addition of _PyImport_RunModInitFunc(), which is strictly focused on running the init func and validating the result. A later PR will take it a step farther by capturing error information rather than raising exceptions.
FWIW, this change also helps readers by clarifying a bit more about what happens when an extension/builtin module is imported.
These are cleanups I've pulled out of gh-118116. Mostly, this change moves code around to align with some future changes and to improve clarity a little. There is one very small change in behavior: we now add the module to the per-interpreter caches after updating the global state, rather than before.
This is a collection of very basic cleanups I've pulled out of gh-118116. It is mostly renaming variables and moving a couple bits of code in functionally equivalent ways.
<pycore_time.h> include is no longer needed to get the PyTime_t type
in internal header files. This type is now provided by <Python.h>
include. Add <pycore_time.h> includes to C files instead.
This replaces some usages of PyThread_type_lock with PyMutex, which does not require memory allocation to initialize.
This simplifies some of the runtime initialization and is also one step towards avoiding changing the default raw memory allocator during initialize/finalization, which can be non-thread-safe in some circumstances.
No longer export _PyCompile_AstOptimize() internal C API function.
Change comment style to "// comment" and add comment explaining why
other functions have to be exported.
* Add missing includes.
* Remove unused includes.
* Update old include/symbol names to newer names.
* Mention at least one included symbol.
* Sort includes.
* Update Tools/cases_generator/generate_cases.py used to generated
pycore_opcode_metadata.h.
* Update Parser/asdl_c.py used to generate pycore_ast.h.
* Cleanup also includes in _testcapimodule.c and _testinternalcapi.c.
* pycore_intrinsics.h does nothing if included twice
(add #ifndef and #define).
* Update Tools/cases_generator/generate_cases.py to generate the
Py_BUILD_CORE test.
* _bz2, _lzma, _opcode and zlib extensions now define the
Py_BUILD_CORE_MODULE macro to use internal headers
(pycore_code.h, pycore_intrinsics.h and pycore_blocks_output_buffer.h).
This fixes a crasher due to a race condition, triggered infrequently when two isolated (own GIL) subinterpreters simultaneously initialize their sys or builtins modules. The crash happened due the combination of the "detached" thread state we were using and the "last holder" logic we use for the GIL. It turns out it's tricky to use the same thread state for different threads. Who could have guessed?
We solve the problem by eliminating the one object we were still sharing between interpreters. We replace it with a low-level hashtable, using the "raw" allocator to avoid tying it to the main interpreter.
We also remove the accommodations for "detached" thread states, which were a dubious idea to start with.
No longer export these 5 internal C API variables:
* _PyBufferWrapper_Type
* _PyImport_FrozenBootstrap
* _PyImport_FrozenStdlib
* _PyImport_FrozenTest
* _Py_SwappedOp
Fix the definition of these internal functions, replace PyAPI_DATA()
with PyAPI_FUNC():
* _PyImport_ClearExtension()
* _PyObject_IsFreed()
* _PyThreadState_GetCurrent()
* Remove private _PyImport C API functions: move them to the internal
C API (pycore_import.h).
* No longer export most of these private functions.
* _testcapi avoids private _PyImport_GetModuleAttrString().
Remove the "cpython/pytime.h" header file: it only contained private
functions. Move functions to the internal pycore_time.h header file.
Move tests from _testcapi to _testinternalcapi. Rename also test
methods to have the same name than tested C functions.
No longer export these functions:
* _PyTime_Add()
* _PyTime_As100Nanoseconds()
* _PyTime_FromMicrosecondsClamp()
* _PyTime_FromTimespec()
* _PyTime_FromTimeval()
* _PyTime_GetPerfCounterWithInfo()
* _PyTime_MulDiv()
Sharing mutable (or non-immortal) objects between interpreters is generally not safe. We can work around that but not easily.
There are two restrictions that are critical for objects that break interpreter isolation.
The first is that the object's state be guarded by a global lock. For now the GIL meets this requirement, but a granular global lock is needed once we have a per-interpreter GIL.
The second restriction is that the object (and, for a container, its items) be deallocated/resized only when the interpreter in which it was allocated is the current one. This is because every interpreter has (or will have, see gh-101660) its own object allocator. Deallocating an object with a different allocator can cause crashes.
The dict for the cache of module defs is completely internal, which simplifies what we have to do to meet those requirements. To do so, we do the following:
* add a mechanism for re-using a temporary thread state tied to the main interpreter in an arbitrary thread
* add _PyRuntime.imports.extensions.main_tstate`
* add _PyThreadState_InitDetached() and _PyThreadState_ClearDetached() (pystate.c)
* add _PyThreadState_BindDetached() and _PyThreadState_UnbindDetached() (pystate.c)
* make sure the cache dict (_PyRuntime.imports.extensions.dict) and its items are all owned by the main interpreter)
* add a placeholder using for a granular global lock
Note that the cache is only used for legacy extension modules and not for multi-phase init modules.
https://github.com/python/cpython/issues/100227
Specific changes:
* move the import lock to PyInterpreterState
* move the "find_and_load" diagnostic state to PyInterpreterState
Note that the import lock exists to keep multiple imports of the same module in the same interpreter (but in different threads) from stomping on each other. Independently, we use a distinct global lock to protect globally shared import state, especially related to loaded extension modules. For now we can rely on the GIL as that lock but with a per-interpreter GIL we'll need a new global lock.
The remaining state in _PyRuntimeState.imports will (probably) continue being global.
https://github.com/python/cpython/issues/100227
Enforcing (optionally) the restriction set by PEP 489 makes sense. Furthermore, this sets the stage for a potential restriction related to a per-interpreter GIL.
This change includes the following:
* add tests for extension module subinterpreter compatibility
* add _PyInterpreterConfig.check_multi_interp_extensions
* add Py_RTFLAGS_MULTI_INTERP_EXTENSIONS
* add _PyImport_CheckSubinterpIncompatibleExtensionAllowed()
* fail iff the module does not implement multi-phase init and the current interpreter is configured to check
https://github.com/python/cpython/issues/98627
This change is almost entirely moving code around and hiding import state behind internal API. We introduce no changes to behavior, nor to non-internal API. (Since there was already going to be a lot of churn, I took this as an opportunity to re-organize import.c into topically-grouped sections of code.) The motivation is to simplify a number of upcoming changes.
Specific changes:
* move existing import-related code to import.c, wherever possible
* add internal API for interacting with import state (both global and per-interpreter)
* use only API outside of import.c (to limit churn there when changing the location, etc.)
* consolidate the import-related state of PyInterpreterState into a single struct field (this changes layout slightly)
* add macros for import state in import.c (to simplify changing the location)
* group code in import.c into sections
*remove _PyState_AddModule()
https://github.com/python/cpython/issues/101758
We actually don't move PyImport_Inittab. Instead, we make a copy that we keep on _PyRuntimeState and use only that after Py_Initialize(). We also prevent folks from modifying PyImport_Inittab (the best we can) after that point.
https://github.com/python/cpython/issues/81057
Currently custom modules (the array set on PyImport_FrozenModules) replace all the frozen stdlib modules. That can be problematic and is unlikely to be what the user wants. This change treats the custom frozen modules as additions instead. They take precedence over all other frozen modules except for those needed to bootstrap the import system. If the "code" field of an entry in the custom array is NULL then that frozen module is treated as disabled, which allows a custom entry to disable a frozen stdlib module.
This change allows us to get rid of is_essential_frozen_module() and simplifies the logic for which frozen modules should be ignored.
https://bugs.python.org/issue45395
In the list of generated frozen modules at the top of Tools/scripts/freeze_modules.py, you will find that some of the modules have a different name than the module (or .py file) that is actually frozen. Let's call each case an "alias". Aliases do not come into play until we get to the (generated) list of modules in Python/frozen.c. (The tool for freezing modules, Programs/_freeze_module, is only concerned with the source file, not the module it will be used for.)
Knowledge of which frozen modules are aliases (and the identity of the original module) normally isn't important. However, this information is valuable when we go to set __file__ on frozen stdlib modules. This change updates Tools/scripts/freeze_modules.py to map aliases to the original module name (or None if not a stdlib module) in Python/frozen.c. We also add a helper function in Python/import.c to look up a frozen module's alias and add the result of that function to the frozen info returned from find_frozen().
https://bugs.python.org/issue45020
Convert the _imp extension module to the multi-phase initialization
API (PEP 489).
* Add _PyImport_BootstrapImp() which fix a bootstrap issue: import
the _imp module before importlib is initialized.
* Add create_builtin() sub-function, used by _imp_create_builtin().
* Initialize PyInterpreterState.import_func earlier, in
pycore_init_builtins().
* Remove references to _PyImport_Cleanup(). This function has been
renamed to finalize_modules() and moved to pylifecycle.c.
PyOS_AfterFork_Child() helper functions now return a PyStatus:
PyOS_AfterFork_Child() is now responsible to handle errors.
* Move _PySignal_AfterFork() to the internal C API
* Add #ifdef HAVE_FORK on _PyGILState_Reinit(), _PySignal_AfterFork()
and _PyInterpreterState_DeleteExceptMain().
* Rename PyImport_Cleanup() to _PyImport_Cleanup() and move it to the
internal C API. Add 'tstate' parameters.
* Remove documentation of _PyImport_Init(), PyImport_Cleanup(),
_PyImport_Fini(). All three were documented as "For internal use
only.".
* Add 'tstate' parameter to many internal import.c functions.
* _PyImportZip_Init() now gets 'tstate' parameter rather than
'interp'.
* Add 'interp' parameter to _PyState_ClearModules() and rename it
to _PyInterpreterState_ClearModules().
* Move private _PyImport_FindBuiltin() to the internal C API; add
'tstate' parameter to it.
* Remove private _PyImport_AddModuleObject() from the C API:
use public PyImport_AddModuleObject() instead.
* Remove private _PyImport_FindExtensionObjectEx() from the C API:
use private _PyImport_FindExtensionObject() instead.
* Add Include/cpython/import.h and Include/internal/pycore_import.h
header files.
* Move _PyImport_ReInitLock() to the internal C API. Don't export the
symbol anymore.
Sam Gross
Kirill Podoprigora
Brett Simmers
Eric Snow
Victor Stinner
Serhiy Storchaka
Dong-hee Na
Victor Stinner