When os.fork() is called (on platforms that support it) all threads but the current one are destroyed in the child process. Consequently we must ensure that all but the associated interpreter are likewise destroyed. The main interpreter is critical for runtime operation, so we must ensure that fork only happens in the main interpreter.
https://bugs.python.org/issue34651
bpo-6721: When os.fork() was called while another thread holds a logging lock, the child process may deadlock when it tries to log. This fixes that by acquiring all logging locks before fork and releasing them afterwards.
A regression test that fails before this change is included.
Within the new unittest itself: There is a small _potential_ due to mixing of fork and a thread in the child process if the parent's thread happened to hold a non-reentrant library call lock (malloc?) when the os.fork() happens. buildbots and time will tell if this actually manifests itself in this test or not. :/ A functionality test that avoids that would be a challenge.
An alternate test that isn't trying to produce the deadlock itself but just checking that the release and acquire calls are made would be the next best alternative if so.
[bpo-34658](https://www.bugs.python.org/issue34658): Fix a rare interpreter unhandled exception state SystemError only
seen when using subprocess with a preexec_fn while an after_parent handler has
been registered with os.register_at_fork and the fork system call fails.
https://bugs.python.org/issue34658
This causes the tearDown code to only unimport the test modules specifically created as part of each test via the self.mkhier method rather than abusing test.support.modules_setup() and the scary test.support.modules_cleanup() code.
https://bugs.python.org/issue34200
Returning EINTR from pthread semaphore or lock acquisition is an optional POSIX
feature. musl does not provide this feature, so some threadsignal tests fail
when Python is built against it.
There's no good way to test for musl, so we skip if we're on Linux and not using
glibc pthreads.
Also, hedge in the threading documentation about when we can provide interrupts
from lock acquisition.
Store a weak reference to stream readerfor breaking strong references
It breaks the strong reference loop between reader and protocol and allows to detect and close the socket if the stream is deleted (garbage collected)
Eric Snow
Yury Selivanov
Tony Flury
Benjamin Peterson
Andrés Delfino
Carol Willing
Eric V. Smith
Raymond Hettinger
Lisa Roach
觉
Gregory P. Smith
Windson yang
Andrew Svetlov
Michael Felt
Ned Deily
Alexey Izbyshev
Oren Milman
Ethan Furman
Bumsik Kim
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