Commit fc6acccb authored by Antoine Pitrou's avatar Antoine Pitrou

Remove outdated statements about threading and imports.

parent 79341e78
......@@ -120,9 +120,7 @@ processes:
print(q.get()) # prints "[42, None, 'hello']"
p.join()
Queues are thread and process safe, but note that they must never
be instantiated as a side effect of importing a module: this can lead
to a deadlock! (see :ref:`threaded-imports`)
Queues are thread and process safe.
**Pipes**
......
......@@ -996,27 +996,3 @@ is equivalent to::
Currently, :class:`Lock`, :class:`RLock`, :class:`Condition`,
:class:`Semaphore`, and :class:`BoundedSemaphore` objects may be used as
:keyword:`with` statement context managers.
.. _threaded-imports:
Importing in threaded code
--------------------------
While the import machinery is thread-safe, there are two key restrictions on
threaded imports due to inherent limitations in the way that thread-safety is
provided:
* Firstly, other than in the main module, an import should not have the
side effect of spawning a new thread and then waiting for that thread in
any way. Failing to abide by this restriction can lead to a deadlock if
the spawned thread directly or indirectly attempts to import a module.
* Secondly, all import attempts must be completed before the interpreter
starts shutting itself down. This can be most easily achieved by only
performing imports from non-daemon threads created through the threading
module. Daemon threads and threads created directly with the thread
module will require some other form of synchronization to ensure they do
not attempt imports after system shutdown has commenced. Failure to
abide by this restriction will lead to intermittent exceptions and
crashes during interpreter shutdown (as the late imports attempt to
access machinery which is no longer in a valid state).
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