Overview

Python 3.12 is probably starting to support a no-gil configuration. PySide should to find the necessary changes to enable that in the PySide project. The anticipated community reaction
is quite huge, since that will make Python really performant.

Currently, there is only a prototype implementation that we are using. It is based on Python nogil-3.9.10-1 with a register machine and different opcodes. This version is by no means the version expected for the fall, when Python 3.12 should come into existence with NoGIL.

It is not clear whether this branch will be continued at all. This depends very much
on business decisions. I just wanted to make sure of the feasibility, but I'm not implementing it yet.
The feasibility is definitely there if they have the right people and time.

Areas in need of thread protection

(to be identified by thread sanitizer).

libshiboken/ Object deletion

• https://codereview.qt-project.org/c/pyside/pyside-setup/+/660549
• Potentially many areas in Object deletion (reuse wrapper map lock?)
• libshiboken setParent()/ removeParent() and destruction maintaining lists of children and pointer to parent in SbkObjectPrivate/ParentInfo

The question is whether one mutex should be used for all this (sort of GIL replacement), Potential candidate
is the existing wrapper mapper lock.

Signal/Slot connections

• https://codereview.qt-project.org/c/pyside/pyside-setup/+/657290/5
• https://codereview.qt-project.org/c/pyside/pyside-setup/+/660548
• (pending) Signal/Slot ConnectionHash in sources/pyside6/libpyside/dynamicslot.cpp:303
• (pending) updateSourceObject() as called by QObject._init_() sources/pyside6/libpyside/pysidesignal.cpp:941 (reported by sanitizer)
• signalInstanceDisconnect sources/pyside6/libpyside/pysidesignal.cpp:719 (reported by sanitizer)
• disconnect_notify

The question is whether one mutex should be used for all of the signal code and the locked areas be extended?

Override handling

• Sbk_GetPyOverride, Spurious evidence so far.

Done

• setNextQObjectMemoryAddr() sources/pyside6/libpysideqml/pysideqmlregistertype.cpp:41 (thread_local?)
• basic compile fixes, removed NoGIL code

References

• py-free-threading.github.io (Tutorial)
• What’s New In Python 3.13
• PEP 703 – Making the Global Interpreter Lock Optional in CPython
• Free threaded vs Limited
• is-free-threading-our-only-option/subinterpreters
• subinterpreters in 3.12
• multi phase-nitialization