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pty.spawn deadlock #96522

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zhangyoufu opened this issue Sep 3, 2022 · 4 comments
Closed

pty.spawn deadlock #96522

zhangyoufu opened this issue Sep 3, 2022 · 4 comments
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type-bug An unexpected behavior, bug, or error

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@zhangyoufu
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zhangyoufu commented Sep 3, 2022 •
edited by bedevere-bot
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Bug report

% yes | python3 -c "import pty; pty.spawn(['cat'])"
y
...
y^CTraceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python3.10/pty.py", line 181, in spawn
    _copy(master_fd, master_read, stdin_read)
  File "/usr/lib/python3.10/pty.py", line 161, in _copy
    _writen(master_fd, data)
  File "/usr/lib/python3.10/pty.py", line 127, in _writen
    n = os.write(fd, data)
KeyboardInterrupt

You will see 2048 lines of y due to tty echo, then the output stops and hangs forever.
Both python and cat block on write, waiting each other consume something from pty buffer.

Your environment

Tested on Linux/macOS with CPython 3.10.

Linked PRs
@zhangyoufu zhangyoufu added the type-bug An unexpected behavior, bug, or error label Sep 3, 2022
@zhangyoufu
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pty._copy did not check whether the destination fd is writable.

@bedevere-bot bedevere-bot mentioned this issue Sep 7, 2022
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@ambv
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ambv commented Oct 5, 2022

I can reproduce this with main, and the proposed PR does indeed fix the deadlock.

ambv pushed a commit that referenced this issue May 19, 2023
@zhangyoufu
gh-96522: Fix deadlock in pty.spawn (#96639)
9c5aa89
ambv pushed a commit to ambv/cpython that referenced this issue May 19, 2023
@zhangyoufu @ambv
[3.11] pythongh-96522: Fix deadlock in pty.spawn (pythonGH-96639)
38b5d74 
(cherry picked from commit 9c5aa89)

Co-authored-by: Youfu Zhang <1315097+zhangyoufu@users.noreply.github.com>
@bedevere-bot bedevere-bot mentioned this issue May 19, 2023
Merged
ambv added a commit that referenced this issue May 19, 2023
@ambv @zhangyoufu
[3.11] gh-96522: Fix deadlock in pty.spawn (GH-96639) (#104655)
702ce87 
(cherry picked from commit 9c5aa89)

Co-authored-by: Youfu Zhang <1315097+zhangyoufu@users.noreply.github.com>
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ambv commented May 19, 2023

Fixed in 3.11 and 3.12.

@ambv ambv closed this as completed May 19, 2023
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ambv commented May 19, 2023

Thanks, @zhangyoufu! ✨ 🍰 ✨

carljm added a commit to gsallam/cpython_with_perfmap_apii that referenced this issue May 20, 2023
@carljm
Merge branch 'main' into gsallam/main
ea5965a 
* main: (30 commits)
  pythongh-103987: fix several crashes in mmap module (python#103990)
  docs: fix wrong indentation causing rendering error in dis page (python#104661)
  pythongh-94906: Support multiple steps in math.nextafter (python#103881)
  pythongh-104472: Skip `test_subprocess.ProcessTestCase.test_empty_env` if ASAN is enabled (python#104667)
  pythongh-103839: Allow building Tkinter against Tcl 8.7 without external libtommath (pythonGH-103842)
  pythongh-85984: New additions and improvements to the tty library. (python#101832)
  pythongh-104659: Consolidate python examples in enum documentation (python#104665)
  pythongh-92248: Deprecate `type`, `choices`, `metavar` parameters of `argparse.BooleanOptionalAction` (python#103678)
  pythongh-104645: fix error handling in marshal tests (python#104646)
  pythongh-104600: Make type.__type_params__ writable (python#104634)
  pythongh-104602: Add additional test for listcomp with lambda (python#104639)
  pythongh-104640: Disallow walrus in comprehension within type scopes (python#104641)
  pythongh-103921: Rename "type" header in argparse docs (python#104654)
  Improve readability of `typing._ProtocolMeta.__instancecheck__` (python#104649)
  pythongh-96522: Fix deadlock in pty.spawn (python#96639)
  pythonGH-102818: Do not call `PyTraceBack_Here` in sys.settrace trampoline.  (pythonGH-104579)
  pythonGH-103545: Add macOS specific constants for ``os.setpriority`` to ``os`` (python#104606)
  pythongh-104623: Update macOS installer to SQLite 3.42.0 (pythonGH-104624)
  pythongh-104619: never leak comprehension locals to outer locals() (python#104637)
  pythongh-104602: ensure all cellvars are known up front (python#104603)
  ...
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