The `--disable-gil` builds occasionally need to pause all but one thread. Some
examples include:
* Cyclic garbage collection, where this is often called a "stop the world event"
* Before calling `fork()`, to ensure a consistent state for internal data structures
* During interpreter shutdown, to ensure that daemon threads aren't accessing Python objects
This adds the following functions to implement global and per-interpreter pauses:
* `_PyEval_StopTheWorldAll()` and `_PyEval_StartTheWorldAll()` (for the global runtime)
* `_PyEval_StopTheWorld()` and `_PyEval_StartTheWorld()` (per-interpreter)
(The function names may change.)
These functions are no-ops outside of the `--disable-gil` build.
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.
* Move _PyRuntimeState.time to _posixstate.ticks_per_second and
time_module_state.ticks_per_second.
* Add time_module_state.clocks_per_second.
* Rename _PyTime_GetClockWithInfo() to py_clock().
* Rename _PyTime_GetProcessTimeWithInfo() to py_process_time().
* Add process_time_times() helper function, called by
py_process_time().
* os.times() is now always built: no longer rely on HAVE_TIMES.
This moves several general internal APIs out of _xxsubinterpretersmodule.c and into the new Python/crossinterp.c (and the corresponding internal headers).
Specifically:
* _Py_excinfo, etc.: the initial implementation for non-object exception snapshots (in pycore_pyerrors.h and Python/errors.c)
* _PyXI_exception_info, etc.: helpers for passing an exception beween interpreters (wraps _Py_excinfo)
* _PyXI_namespace, etc.: helpers for copying a dict of attrs between interpreters
* _PyXI_Enter(), _PyXI_Exit(): functions that abstract out the transitions between one interpreter and a second that will do some work temporarily
Again, these were all abstracted out of _xxsubinterpretersmodule.c as generalizations. I plan on proposing these as public API at some point.
This is partly to clear this stuff out of pystate.c, but also in preparation for moving some code out of _xxsubinterpretersmodule.c. This change also moves this stuff to the internal API (new: Include/internal/pycore_crossinterp.h). @vstinner did this previously and I undid it. Now I'm re-doing it. :/
We do the following:
* add a per-interpreter XID registry (PyInterpreterState.xidregistry)
* put heap types there (keep static types in _PyRuntimeState.xidregistry)
* clear the registries during interpreter/runtime finalization
* avoid duplicate entries in the registry (when _PyCrossInterpreterData_RegisterClass() is called more than once for a type)
* use Py_TYPE() instead of PyObject_Type() in _PyCrossInterpreterData_Lookup()
The per-interpreter registry helps preserve isolation between interpreters. This is important when heap types are registered, which is something we haven't been doing yet but I will likely do soon.
There is a WIP proposal to enable webassembly stack switching which have been
implemented in v8:
https://github.com/WebAssembly/js-promise-integration
It is not possible to switch stacks that contain JS frames so the Emscripten JS
trampolines that allow calling functions with the wrong number of arguments
don't work in this case. However, the js-promise-integration proposal requires
the [type reflection for Wasm/JS API](https://github.com/WebAssembly/js-types)
proposal, which allows us to actually count the number of arguments a function
expects.
For better compatibility with stack switching, this PR checks if type reflection
is available, and if so we use a switch block to decide the appropriate
signature. If type reflection is unavailable, we should use the current EMJS
trampoline.
We cache the function argument counts since when I didn't cache them performance
was negatively affected.
Co-authored-by: T. Wouters <thomas@python.org>
Co-authored-by: Brett Cannon <brett@python.org>
No longer export _PyUnicode_FromId() internal C API function.
Change comment style to "// comment" and add comment explaining why
other functions have to be exported.
Update Tools/build/generate_token.py to update Include/internal/pycore_token.h
comments.
* 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.
We tried this before with a dict and for all interned strings. That ran into problems due to interpreter isolation. However, exclusively using a per-interpreter cache caused some inconsistency that can eliminate the benefit of interning. Here we circle back to using a global cache, but only for statically allocated strings. We also use a more-basic _Py_hashtable_t for that global cache instead of a dict.
Ideally we would only have the global cache, but the optional isolation of each interpreter's allocator means that a non-static string object must not outlive its interpreter. Thus we would have to store a copy of each such interned string in the global cache, tied to the main interpreter.
This is the culmination of PEP 684 (and of my 8-year long multi-core Python project)!
Each subinterpreter may now be created with its own GIL (via Py_NewInterpreterFromConfig()). If not so configured then the interpreter will share with the main interpreter--the status quo since subinterpreters were added decades ago. The main interpreter always has its own GIL and subinterpreters from Py_NewInterpreter() will always share with the main interpreter.
This is strictly about moving the "obmalloc" runtime state from
`_PyRuntimeState` to `PyInterpreterState`. Doing so improves isolation
between interpreters, specifically most of the memory (incl. objects)
allocated for each interpreter's use. This is important for a
per-interpreter GIL, but such isolation is valuable even without it.
FWIW, a per-interpreter obmalloc is the proverbial
canary-in-the-coalmine when it comes to the isolation of objects between
interpreters. Any object that leaks (unintentionally) to another
interpreter is highly likely to cause a crash (on debug builds at
least). That's a useful thing to know, relative to interpreter
isolation.
Core static types will continue to use the global value. All other types
will use the per-interpreter value. They all share the same range, where
the global types use values < 2^16 and each interpreter uses values
higher than that.
We replace _PyRuntime.tstate_current with a thread-local variable. As part of this change, we add a _Py_thread_local macro in pyport.h (only for the core runtime) to smooth out the compiler differences. The main motivation here is in support of a per-interpreter GIL, but this change also provides some performance improvement opportunities.
Note that we do not provide a fallback to the thread-local, either falling back to the old tstate_current or to thread-specific storage (PyThread_tss_*()). If that proves problematic then we can circle back. I consider it unlikely, but will run the buildbots to double-check.
Also note that this does not change any of the code related to the GILState API, where it uses a thread state stored in thread-specific storage. I suspect we can combine that with _Py_tss_tstate (from here). However, that can be addressed separately and is not urgent (nor critical).
(While this change was mostly done independently, I did take some inspiration from earlier (~2020) work by @markshannon (main...markshannon:threadstate_in_tls) and @vstinner (#23976).)
The function is like Py_AtExit() but for a single interpreter. This is a companion to the atexit module's register() function, taking a C callback instead of a Python one.
We also update the _xxinterpchannels module to use _Py_AtExit(), which is the motivating case. (This is inspired by pain points felt while working on gh-101660.)
We can revisit the options for keeping it global later, if desired. For now the approach seems quite complex, so we've gone with the simpler isolation solution in the meantime.
https://github.com/python/cpython/issues/100227
The essentially eliminates the global variable, with the associated benefits. This is also a precursor to isolating this bit of state to PyInterpreterState.
Folks that currently read _Py_RefTotal directly would have to start using _Py_GetGlobalRefTotal() instead.
https://github.com/python/cpython/issues/102304
We've factored out a struct from the two PyThreadState fields. This accomplishes two things:
* make it clear that the trashcan-related code doesn't need any other parts of PyThreadState
* allows us to use the trashcan mechanism even when there isn't a "current" thread state
We still expect the caller to hold the GIL.
https://github.com/python/cpython/issues/59956
The objective of this change is to help make the GILState-related code easier to understand. This mostly involves moving code around and some semantically equivalent refactors. However, there are a also a small number of slight changes in structure and behavior:
* tstate_current is moved out of _PyRuntimeState.gilstate
* autoTSSkey is moved out of _PyRuntimeState.gilstate
* autoTSSkey is initialized earlier
* autoTSSkey is re-initialized (after fork) earlier
https://github.com/python/cpython/issues/59956
* move _PyRuntime.global_objects.interned to _PyRuntime.cached_objects.interned_strings (and use _Py_CACHED_OBJECT())
* rename _PyRuntime.global_objects to _PyRuntime.static_objects
(This also relates to gh-96075.)
https://github.com/python/cpython/issues/90111
The global allocators were stored in 3 static global variables: _PyMem_Raw, _PyMem, and _PyObject. State for the "small block" allocator was stored in another 13. That makes a total of 16 global variables. We are moving all 16 to the _PyRuntimeState struct as part of the work for gh-81057. (If PEP 684 is accepted then we will follow up by moving them all to PyInterpreterState.)
https://github.com/python/cpython/issues/81057
He Weidong
Sam Gross
Victor Stinner
Eric Snow
Irit Katriel
Donghee Na
Hood Chatham
Mark Shannon
Pablo Galindo Salgado
Gabriele N. Tornetta
Виталий Дмитриев