Biased reference counting maintains two refcount fields in each object:
`ob_ref_local` and `ob_ref_shared`. The true refcount is the sum of these two
fields. In some cases, when refcounting operations are split across threads,
the ob_ref_shared field can be negative (although the total refcount must be
at least zero). In this case, the thread that decremented the refcount
requests that the owning thread give up ownership and merge the refcount
fields.
Fixes a few issues related to refleak tracking in the free-threaded build:
- Count blocks in abandoned segments
- Call `_mi_page_free_collect` earlier during heap traversal in order to get an accurate count of blocks in use.
- Add missing refcount tracking in `_Py_DecRefSharedDebug` and `_Py_ExplicitMergeRefcount`.
- Pause threads in `get_num_global_allocated_blocks` to ensure that traversing the mimalloc heaps is safe.
This changes a number of internal usages of `PyDict_SetDefault` to use `PyDict_SetDefaultRef`.
Co-authored-by: Erlend E. Aasland <erlend.aasland@protonmail.com>
Starts adding thread safety to dict objects.
Use @critical_section for APIs which are exposed via argument clinic and don't directly correlate with a public C API which needs to acquire the lock
Use a _lock_held suffix for keeping changes to complicated functions simple and just wrapping them with a critical section
Acquire and release the lock in an existing function where it won't be overly disruptive to the existing logic
This marks dead ThreadHandles as non-joinable earlier in
`PyOS_AfterFork_Child()` before we execute any Python code. The handles
are stored in a global linked list in `_PyRuntimeState` because `fork()`
affects the entire process.
We do not want to add locking in `tp_traverse` slot implementations.
Instead, stop the world when calling `gc.get_referents`. Note that the the
stop the world call is a no-op in the default build.
Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>
The `PyDict_SetDefaultRef` function is similar to `PyDict_SetDefault`,
but returns a strong reference through the optional `**result` pointer
instead of a borrowed reference.
Co-authored-by: Petr Viktorin <encukou@gmail.com>
Add optional 'filter' parameter to iterdump() that allows a "LIKE"
pattern for filtering database objects to dump.
Co-authored-by: Erlend E. Aasland <erlend@python.org>
When expanding `**` wildcards, ensure we add a trailing slash to the
topmost directory path. This matches `glob.glob()` behaviour:
>>> glob.glob('dirA/**', recursive=True)
['dirA/', 'dirA/dirB', 'dirA/dirB/dirC']
This does not affect `pathlib.Path.glob()`, because trailing slashes aren't
supported in pathlib proper.
Fix race between `_PyParkingLot_Park` and `_PyParkingLot_UnparkAll` when handling interrupts
There is a potential race when `_PyParkingLot_UnparkAll` is executing in
one thread and another thread is unblocked because of an interrupt in
`_PyParkingLot_Park`. Consider the following scenario:
1. Thread T0 is blocked[^1] in `_PyParkingLot_Park` on address `A`.
2. Thread T1 executes `_PyParkingLot_UnparkAll` on address `A`. It
finds the `wait_entry` for `T0` and unlinks[^2] its list node.
3. Immediately after (2), T0 is woken up due to an interrupt. It
then segfaults trying to unlink[^3] the node that was previously
unlinked in (2).
To fix this we mark each waiter as unparking before releasing the bucket
lock. `_PyParkingLot_Park` will wait to handle the coming wakeup, and not
attempt to unlink the node, when this field is set. `_PyParkingLot_Unpark`
does this already, presumably to handle this case.
Change the somewhat vague "listed below" to "listed in this chapter" in Doc/library/exceptions.rst.
The exceptions are listed in multiple sections after two intermediate sections.
---------
Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>
