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python/aqmp: fix race condition in legacy.py

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legacy.py provides a synchronous model. iotests frequently uses this
paradigm:

 - create QMP client object
 - start QEMU process
 - await connection from QEMU process

In the switch from sync to async QMP, the QMP client object stopped
calling bind() and listen() during the QMP object creation step, which
creates a race condition if the QEMU process dials in too quickly.

With refactoring out of the way, restore the former behavior of calling
bind() and listen() during __init__() to fix this race condition.

Signed-off-by: John Snow <jsnow@redhat.com>
Acked-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20220225205948.3693480-10-jsnow@redhat.com
[Expanded commit message. --js]
Signed-off-by: John Snow <jsnow@redhat.com>
This commit is contained in:
John Snow 2022-02-25 15:59:47 -05:00
parent 481607c7d3
commit 673856f9d8
1 changed files with 2 additions and 5 deletions
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7
python/qemu/aqmp/legacy.py
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@ -57,7 +57,7 @@ class QEMUMonitorProtocol(qemu.qmp.QEMUMonitorProtocol):
self._timeout: Optional[float] = None
if server:
self._aqmp._bind_hack(address) # pylint: disable=protected-access
self._sync(self._aqmp.start_server(address))
_T = TypeVar('_T')
@ -90,10 +90,7 @@ class QEMUMonitorProtocol(qemu.qmp.QEMUMonitorProtocol):
self._aqmp.await_greeting = True
self._aqmp.negotiate = True
self._sync(
self._aqmp.start_server_and_accept(self._address),
timeout
)
self._sync(self._aqmp.accept(), timeout)
ret = self._get_greeting()
assert ret is not None