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bpo-38982: Fix asyncio PidfdChildWatcher on waitpid() error #17477

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Merged
vstinner merged 1 commit into from
Dec 6, 2019
Merged

bpo-38982: Fix asyncio PidfdChildWatcher on waitpid() error #17477

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15 changes: 13 additions & 2 deletions Lib/asyncio/unix_events.py
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Original file line number Diff line number Diff line change
Expand Up @@ -930,9 +930,20 @@ def add_child_handler(self, pid, callback, *args):
def _do_wait(self, pid):
pidfd, callback, args = self._callbacks.pop(pid)
self._loop._remove_reader(pidfd)
_, status = os.waitpid(pid, 0)
try:
_, status = os.waitpid(pid, 0)
except ChildProcessError:
# The child process is already reaped
# (may happen if waitpid() is called elsewhere).
returncode = 255
logger.warning(
"child process pid %d exit status already read: "
" will report returncode 255",
pid)
else:
returncode = _compute_returncode(status)

os.close(pidfd)
returncode = _compute_returncode(status)
callback(pid, returncode, *args)

def remove_child_handler(self, pid):
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5 changes: 5 additions & 0 deletions Misc/NEWS.d/next/Library/2019-12-05-18-21-26.bpo-38982.W3u-03.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
Fix asyncio ``PidfdChildWatcher``: handle ``waitpid()`` error. If
``waitpid()`` is called elsewhere, ``waitpid()`` call fails with
:exc:`ChildProcessError`: use return code 255 in this case, and log a
warning. It ensures that the pidfd file descriptor is closed if this error
occurs.