gh-140734: fix off-by-one error when comparing to `_SUN_PATH_MAX` (GH-140903)
The limit includes a NULL terminator.
(cherry picked from commit 9a19900673)
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
gh-126631: gh-137996: fix pre-loading of `__main__`
The `main_path` parameter was renamed `init_main_from_name`, update the
forkserver code accordingly. This was leading to slower startup times when people
were trying to preload the main module.
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(cherry picked from commit 0912b3a6db)
Co-authored-by: Duane Griffin <duaneg@dghda.com>
gh-118981: multiprocessing.popen_spawn_posix, fix potential hang (gh-118982)
fix potential hang.
It can happen that the child crashes right in the beginning for whatever reason. In this case, the parent will hang when writing into the pipe, because the child fd is not closed yet.
The normal pattern is to close the child fds right after the child proc is forked/executed/spawned, so when the child dies, then also the pipes will be closed, and there will be no hang (the parent gets SIGPIPE instead).
(cherry picked from commit 8ed5a2b56c)
Co-authored-by: Albert Zeyer <albzey@gmail.com>
gh-131788: make resource_tracker re-entrant safe (GH-131787)
(cherry picked from commit f24a012350)
Co-authored-by: Thomas Grainger <tagrain@gmail.com>
Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Co-authored-by: Gregory P. Smith <greg@krypto.org>
* gh-132124: improve safety nets for creating AF_UNIX socket files (GH-134085)
* ensure that we can create AF_UNIX socket files
* emit a warning if system-wide temporary directory is used
(cherry picked from commit 1a07a01014)
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
* rename warn -> _warn for the 3.13.x backport
* Update Misc/NEWS.d/next/Library/2025-05-16-12-40-37.gh-issue-132124.T_5Odx.rst
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Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
Co-authored-by: Gregory P. Smith <greg@krypto.org>
gh-135335: flush stdout/stderr in forkserver after preloading modules (GH-135338)
If a preloaded module writes to stdout or stderr, and the stream is buffered,
child processes will inherit the buffered data after forking. Attempt to
prevent this by flushing the streams after preload.
(cherry picked from commit 9877d191f4)
Co-authored-by: Duane Griffin <duaneg@dghda.com>
Co-authored-by: Mikhail Efimov <efimov.mikhail@gmail.com>
Co-authored-by: Victor Stinner <vstinner@python.org>
gh-80334: fix multiprocessing.freeze_support for other spawn platforms (GH-134462)
Doc/library/multiprocessing.rst: freeze_support: Change to specify spawn method instead of platform
Have multiprocessing.freeze_support() enable on spawn, not just win32.
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(cherry picked from commit 80284b5c5e)
Co-authored-by: Eddy Mulyono <eddymul@gmail.com>
Co-authored-by: Gregory P. Smith <greg@krypto.org>
gh-88887: Cleanup `multiprocessing.resource_tracker.ResourceTracker` upon deletion (GH-130429)
(cherry picked from commit f53e7de6a8)
Co-authored-by: luccabb <32229669+luccabb@users.noreply.github.com>
Co-authored-by: Victor Stinner <vstinner@python.org>
Co-authored-by: Gregory P. Smith <greg@krypto.org>
remove type annotations from multiprocessing. (GH-129381)
* remove type annotations from multiprocessing.
One of them was technically invalid per typing specs... but since we're not
checking these in the stdlib today lets elide them.
https://discuss.python.org/t/static-type-annotations-in-cpython/65068/13
* use the actual comment style annotation format
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(cherry picked from commit 71aecc284e)
Co-authored-by: Gregory P. Smith <greg@krypto.org>
Co-authored-by: 🇺🇦 Sviatoslav Sydorenko (Святослав Сидоренко) <wk.cvs.github@sydorenko.org.ua>
gh-127586: multiprocessing.Pool does not properly restore blocked signals (try 2) (GH-128011)
Correct pthread_sigmask in resource_tracker to restore old signals
Using SIG_UNBLOCK to remove blocked "ignored signals" may accidentally
cause side effects if the calling parent already had said signals
blocked to begin with and did not intend to unblock them when
creating a pool. Use SIG_SETMASK instead with the previous mask of
blocked signals to restore the original blocked set.
(cherry picked from commit aeb9b65aa2)
Co-authored-by: Stephen Hansen <stephen.paul.hansen@gmail.com>
Co-authored-by: Peter Bierma <zintensitydev@gmail.com>
Co-authored-by: Gregory P. Smith <greg@krypto.org>
Add the missing `f` on an f-string error message in multiprocessing. (GH-127462)
(cherry picked from commit 11c01092d5)
Co-authored-by: Gregory P. Smith <greg@krypto.org>
Proxes of shared objects register a Finalizer in BaseProxy._incref(), and it
will call BaseProxy._decref() when it is GCed. This may cause a race condition
with Pool(maxtasksperchild=None) on Windows.
A connection would be closed and raised TypeError when a GC occurs between
_ConnectionBase._check_writable() and _ConnectionBase._send_bytes() in
_ConnectionBase.send() in the second or later task, and a new object
is allocated that shares the id() of a previously deleted one.
Instead of using the id() of the token (or the proxy), use a unique,
non-reusable number.
(cherry picked from commit ba088c8f9c)
Co-authored-by: Petr Viktorin <encukou@gmail.com>
Co-authored-by: Akinori Hattori <hattya@gmail.com>
gh-117378: Fix multiprocessing forkserver preload sys.path inheritance. (GH-126538)
`sys.path` was not properly being sent from the parent process when launching
the multiprocessing forkserver process to preload imports. This bug has been
there since the forkserver start method was introduced in Python 3.4. It was
always _supposed_ to inherit `sys.path` the same way the spawn method does.
Observable behavior change: A `''` value in `sys.path` will now be replaced in
the forkserver's `sys.path` with an absolute pathname
`os.path.abspath(os.getcwd())` saved at the time that `multiprocessing` was
imported in the parent process as it already was when using the spawn start
method. **This will only be observable during forkserver preload imports**.
The code invoked before calling things in another process already correctly sets `sys.path`.
Which is likely why this went unnoticed for so long as a mere performance issue in
some configurations.
A workaround for the bug on impacted Pythons is to set PYTHONPATH in the
environment before multiprocessing's forkserver process was started. Not perfect
as that is then inherited by other children, etc, but likely good enough for many
people's purposes.
(cherry picked from commit 9d08423b6e)
Co-authored-by: Gregory P. Smith <greg@krypto.org>
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
This builds on https://github.com/python/cpython/pull/106807, which adds
a return code to ResourceTracker, to make future debugging easier.
Testing this “in situ” proved difficult, since the global ResourceTracker is
involved in test infrastructure. So, the tests here create a new instance and
feed it fake data.
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Co-authored-by: Yonatan Bitton <yonatan.bitton@perception-point.io>
Co-authored-by: Yonatan Bitton <bityob@gmail.com>
Co-authored-by: Antoine Pitrou <antoine@python.org>
We add _winapi.BatchedWaitForMultipleObjects to wait for larger numbers of handles.
This is an internal module, hence undocumented, and should be used with caution.
Check the docstring for info before using BatchedWaitForMultipleObjects.
`_multiprocessing` is only used under the `if _winapi:` block, this moves the import to be within the `_winapi` ImportError handling try/except for equivalent treatment.
Increase the backlog for multiprocessing.connection.Listener` objects created
by `multiprocessing.manager` and `multiprocessing.resource_sharer` to
significantly reduce the risk of getting a connection refused error when creating
a `multiprocessing.connection.Connection` to them.
On Windows, Process.terminate() no longer sets the returncode
attribute to always call WaitForSingleObject() in Process.wait().
Previously, sometimes the process was still running after
TerminateProcess() even if GetExitCodeProcess() is not STILL_ACTIVE.
Add a track parameter to shared memory to allow resource tracking via the side-launched resource tracker process to be disabled on platforms that use it (POSIX).
This allows people who do not want automated cleanup at process exit because they are using the shared memory with processes not participating in Python's resource tracking to use the shared_memory API.
Co-authored-by: Łukasz Langa <lukasz@langa.pl>
Co-authored-by: Guido van Rossum <gvanrossum@gmail.com>
Co-authored-by: Antoine Pitrou <pitrou@free.fr>
Co-authored-by: Gregory P. Smith <greg@krypto.org>
Make `multiprocessing.managers.{DictProxy,ListProxy}` generic for type annotation use. `ListProxy[str]` for example.
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
Co-authored-by: Gregory P. Smith <greg@krypto.org>
concurrent.futures: The *executor manager thread* now catches
exceptions when adding an item to the *call queue*. During Python
finalization, creating a new thread can now raise RuntimeError. Catch
the exception and call terminate_broken() in this case.
Add test_python_finalization_error() to test_concurrent_futures.
concurrent.futures._ExecutorManagerThread changes:
* terminate_broken() no longer calls shutdown_workers() since the
call queue is no longer working anymore (read and write ends of
the queue pipe are closed).
* terminate_broken() now terminates child processes, not only
wait until they complete.
* _ExecutorManagerThread.terminate_broken() now holds shutdown_lock
to prevent race conditons with ProcessPoolExecutor.submit().
multiprocessing.Queue changes:
* Add _terminate_broken() method.
* _start_thread() sets _thread to None on exception to prevent
leaking "dangling threads" even if the thread was not started
yet.
On Windows, multiprocessing Popen.terminate() now catchs
PermissionError and get the process exit code. If the process is
still running, raise again the PermissionError. Otherwise, the
process terminated as expected: store its exit code.
Follow-up of gh-107219.
* Only close the connection writer on Windows.
* Also use existing constant _winapi.ERROR_OPERATION_ABORTED instead of
WSA_OPERATION_ABORTED.
Fix a race condition in concurrent.futures. When a process in the
process pool was terminated abruptly (while the future was running or
pending), close the connection write end. If the call queue is
blocked on sending bytes to a worker process, closing the connection
write end interrupts the send, so the queue can be closed.
Changes:
* _ExecutorManagerThread.terminate_broken() now closes
call_queue._writer.
* multiprocessing PipeConnection.close() now interrupts
WaitForMultipleObjects() in _send_bytes() by cancelling the
overlapped operation.
gh-107275 introduced a regression where a SemLock would fail being passed along nested child processes, as the `is_fork_ctx` attribute would be left missing after the first deserialization.
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Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Co-authored-by: Antoine Pitrou <pitrou@free.fr>
Ensure multiprocessing SemLock is valid for spawn Process before serializing it.
Creating a multiprocessing SemLock with a fork context, and then trying to pass it to a spawn-created Process, would segfault if not detected early.
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Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Co-authored-by: Antoine Pitrou <pitrou@free.fr>
Adding the `rtype_cache` to the `warnings.warn` message improves the
previous, somewhat vague message from
```
/Users/username/cpython/Lib/multiprocessing/resource_tracker.py:224: UserWarning: resource_tracker: There appear to be 6 leaked semaphore objects to clean up at shutdown
```
to
```
/Users/username/cpython/Lib/multiprocessing/resource_tracker.py:224: UserWarning: resource_tracker: There appear to be 6 leaked semaphore objects to clean up at shutdown: {'/mp-yor5cvj8', '/mp-10jx8eqr', '/mp-eobsx9tt', '/mp-0lml23vl', '/mp-9dgtsa_m', '/mp-frntyv4s'}
```
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Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Prevent `multiprocessing.spawn` from failing to *import* in environments
where `sys.executable` is `None`. This regressed in 3.11 with the addition
of support for path-like objects in multiprocessing.
Adds a test decorator to have tests only run when part of test_multiprocessing_spawn to `_test_multiprocessing.py` so we can start to avoid re-running the same not-global-state specific test in all 3 modes when there is no need.
Fix a race condition in the internal `multiprocessing.process` cleanup
logic that could manifest as an unintended `AttributeError` when calling
`BaseProcess.close()`.
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Co-authored-by: Oleg Iarygin <oleg@arhadthedev.net>
Co-authored-by: Gregory P. Smith <greg@krypto.org>
bpo-17258: `multiprocessing` now supports stronger HMAC algorithms for inter-process connection authentication rather than only HMAC-MD5.
Signed-off-by: Christian Heimes <christian@python.org>
gpshead: I Reworked to be more robust while keeping the idea.
The protocol modification idea remains, but we now take advantage of the
message length as an indicator of legacy vs modern protocol version. No
more regular expression usage. We now default to HMAC-SHA256, but do so
in a way that will be compatible when communicating with older clients
or older servers. No protocol transition period is needed.
More integration tests to verify these claims remain true are required. I'm
unaware of anyone depending on multiprocessing connections between
different Python versions.
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Signed-off-by: Christian Heimes <christian@python.org>
Co-authored-by: Gregory P. Smith [Google] <greg@krypto.org>
This starts the process. Users who don't specify their own start method
and use the default on platforms where it is 'fork' will see a
DeprecationWarning upon multiprocessing.Pool() construction or upon
multiprocessing.Process.start() or concurrent.futures.ProcessPool use.
See the related issue and documentation within this change for details.
