Changes to the function version cache:
- In addition to the function object, also store the code object,
and allow the latter to be retrieved even if the function has been evicted.
- Stop assigning new function versions after a critical attribute (e.g. `__code__`)
has been modified; the version is permanently reset to zero in this case.
- Changes to `__annotations__` are no longer considered critical. (This fixes gh-109998.)
Changes to the Tier 2 optimization machinery:
- If we cannot map a function version to a function, but it is still mapped to a code object,
we continue projecting the trace.
The operand of the `_PUSH_FRAME` and `_POP_FRAME` opcodes can be either NULL,
a function object, or a code object with the lowest bit set.
This allows us to trace through code that calls an ephemeral function,
i.e., a function that may not be alive when we are constructing the executor,
e.g. a generator expression or certain nested functions.
We will lose globals removal inside such functions,
but we can still do other peephole operations
(and even possibly [call inlining](https://github.com/python/cpython/pull/116290),
if we decide to do it), which only need the code object.
As before, if we cannot retrieve the code object from the cache, we stop projecting.
Split `_PyThreadState_DeleteExcept` into two functions:
- `_PyThreadState_RemoveExcept` removes all thread states other than one
passed as an argument. It returns the removed thread states as a
linked list.
- `_PyThreadState_DeleteList` deletes those dead thread states. It may
call destructors, so we want to "start the world" before calling
`_PyThreadState_DeleteList` to avoid potential deadlocks.
I added it quite a while ago as a strategy for managing interpreter lifetimes relative to the PEP 554 (now 734) implementation. Relatively recently I refactored that implementation to no longer rely on InterpreterID objects. Thus now I'm removing it.
Add Py_GetConstant() and Py_GetConstantBorrowed() functions.
In the limited C API version 3.13, getting Py_None, Py_False,
Py_True, Py_Ellipsis and Py_NotImplemented singletons is now
implemented as function calls at the stable ABI level to hide
implementation details. Getting these constants still return borrowed
references.
Add _testlimitedcapi/object.c and test_capi/test_object.py to test
Py_GetConstant() and Py_GetConstantBorrowed() functions.
Mostly we unify the two different implementations of the conversion code (from PyObject * to int64_t. We also drop the PyArg_ParseTuple()-style converter function, as well as rename and move PyInterpreterID_LookUp().
Somehow we ended up with two separate counter variables tracking "the next function version".
Most likely this was a historical accident where an old branch was updated incorrectly.
This PR merges the two counters into a single one: `interp->func_state.next_version`.
Defining a type twice is a C11 feature and so makes the C API
incompatible with C99. Fix the issue by only defining the type once.
Example of warning (treated as an error):
In file included from Include/Python.h:122:
Include/cpython/optimizer.h:77:3: error: redefinition of typedef
'_PyOptimizerObject' is a C11 feature [-Werror,-Wtypedef-redefinition]
} _PyOptimizerObject;
^
build/Include/cpython/optimizer.h:60:35: note: previous definition is here
typedef struct _PyOptimizerObject _PyOptimizerObject;
^
There is a race between when `Thread._tstate_lock` is released[^1] in `Thread._wait_for_tstate_lock()`
and when `Thread._stop()` asserts[^2] that it is unlocked. Consider the following execution
involving threads A, B, and C:
1. A starts.
2. B joins A, blocking on its `_tstate_lock`.
3. C joins A, blocking on its `_tstate_lock`.
4. A finishes and releases its `_tstate_lock`.
5. B acquires A's `_tstate_lock` in `_wait_for_tstate_lock()`, releases it, but is swapped
out before calling `_stop()`.
6. C is scheduled, acquires A's `_tstate_lock` in `_wait_for_tstate_lock()` but is swapped
out before releasing it.
7. B is scheduled, calls `_stop()`, which asserts that A's `_tstate_lock` is not held.
However, C holds it, so the assertion fails.
The race can be reproduced[^3] by inserting sleeps at the appropriate points in
the threading code. To do so, run the `repro_join_race.py` from the linked repo.
There are two main parts to this PR:
1. `_tstate_lock` is replaced with an event that is attached to `PyThreadState`.
The event is set by the runtime prior to the thread being cleared (in the same
place that `_tstate_lock` was released). `Thread.join()` blocks waiting for the
event to be set.
2. `_PyInterpreterState_WaitForThreads()` provides the ability to wait for all
non-daemon threads to exit. To do so, an `is_daemon` predicate was added to
`PyThreadState`. This field is set each time a thread is created. `threading._shutdown()`
now calls into `_PyInterpreterState_WaitForThreads()` instead of waiting on
`_tstate_lock`s.
[^1]: 441affc9e7/Lib/threading.py (L1201)
[^2]: 441affc9e7/Lib/threading.py (L1115)
[^3]: 8194653279
---------
Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Co-authored-by: Antoine Pitrou <antoine@python.org>
Return 0 on success. Set an exception and return -1 on error.
Fix os.timerfd_settime(): properly report exceptions on
_PyTime_FromSecondsDouble() failure.
No longer export _PyTime_FromSecondsDouble().
In free-threaded builds, running with `PYTHON_GIL=0` will now disable the
GIL. Follow-up issues track work to re-enable the GIL when loading an
incompatible extension, and to disable the GIL by default.
In order to support re-enabling the GIL at runtime, all GIL-related data
structures are initialized as usual, and disabling the GIL simply sets a flag
that causes `take_gil()` and `drop_gil()` to return early.
Revert "gh-115398: Increment PyExpat_CAPI_MAGIC for SetReparseDeferralEnabled addition (GH-116301)"
This reverts part of commit eda2963378. Why? this comment buried in an earlier code review explains:
I checked again how that value is used in practice, it's here:
0c80da4c14/Modules/_elementtree.c (L4363-L4372)
Based on that code my understanding is that loading bigger structs from the future is considered okay unless `PyExpat_CAPI_MAGIC` differs, which implies that (1) magic needs to stay the same to support loading the future from the past and (2) that `PyExpat_CAPI_MAGIC` should only ever change for changes that do not increase size (but keep it constant).
To summarize, that supports your argument.
I checked branches 3.8, 3.9, 3.10, 3.11, 3.12 now and they all have the same comparison code there so reverting that magic string bump will support seamless backporting.
This implements the delayed reuse of mimalloc pages that contain Python
objects in the free-threaded build.
Allocations of the same size class are grouped in data structures called
pages. These are different from operating system pages. For thread-safety, we
want to ensure that memory used to store PyObjects remains valid as long as
there may be concurrent lock-free readers; we want to delay using it for
other size classes, in other heaps, or returning it to the operating system.
When a mimalloc page becomes empty, instead of immediately freeing it, we tag
it with a QSBR goal and insert it into a per-thread state linked list of
pages to be freed. When mimalloc needs a fresh page, we process the queue and
free any still empty pages that are now deemed safe to be freed. Pages
waiting to be freed are still available for allocations of the same size
class and allocating from a page prevent it from being freed. There is
additional logic to handle abandoned pages when threads exit.
This sets `MI_DEBUG` to `2` in debug builds to enable `mi_assert_internal()`
calls. Expensive internal assertions are not enabled.
This also disables an assertion in free-threaded builds that would be
triggered by the free-threaded GC because we traverse heaps that are not
owned by the current thread.
* Increment PyExpat_CAPI_MAGIC due to SetReparseDeferralEnabled addition.
This is a followup to git commit
6a95676bb5 from Github PR #115623.
* RESTify news API list.
Make `_thread.ThreadHandle` thread-safe in free-threaded builds
We protect the mutable state of `ThreadHandle` using a `_PyOnceFlag`.
Concurrent operations (i.e. `join` or `detach`) on `ThreadHandle` block
until it is their turn to execute or an earlier operation succeeds.
Once an operation has been applied successfully all future operations
complete immediately.
The `join()` method is now idempotent. It may be called multiple times
but the underlying OS thread will only be joined once. After `join()`
succeeds, any future calls to `join()` will succeed immediately.
The internal thread handle `detach()` method has been removed.
Allow controlling Expat >=2.6.0 reparse deferral (CVE-2023-52425) by adding five new methods:
- `xml.etree.ElementTree.XMLParser.flush`
- `xml.etree.ElementTree.XMLPullParser.flush`
- `xml.parsers.expat.xmlparser.GetReparseDeferralEnabled`
- `xml.parsers.expat.xmlparser.SetReparseDeferralEnabled`
- `xml.sax.expatreader.ExpatParser.flush`
Based on the "flush" idea from https://github.com/python/cpython/pull/115138#issuecomment-1932444270 .
### Notes
- Please treat as a security fix related to CVE-2023-52425.
Includes code suggested-by: Snild Dolkow <snild@sony.com>
and by core dev Serhiy Storchaka.
Malcolm Smith
Guido van Rossum
Sam Gross
Michael Droettboom
Eric Snow
Victor Stinner
Serhiy Storchaka
Mark Shannon
Bogdan Romanyuk
mpage
Thomas Wouters
Matthias Diener
Brett Simmers
Donghee Na
Sergey B Kirpichev
Dino Viehland
Ken Jin
Sebastian Pipping
cui fliter
Gregory P. Smith
Brett Cannon