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authorJohn Snow <jsnow@redhat.com>2020-10-09 13:51:23 -0400
committerJohn Snow <jsnow@redhat.com>2020-10-20 15:00:06 -0400
commit39cf73c3494045b4418c9c1db8e803640e2150dc (patch)
treea87dddc8e040a7819cafe109983c38ed02fc00df /python
parentd5cca076c3a1ac55f25792fae4fae2b0b1f71e8e (diff)
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python/qemu/qmp.py: Fix settimeout operation
We enabled callers to interface directly with settimeout, but this reacts poorly with blocking/nonblocking operation; as they are using the same internal mechanism. 1. Whenever we change the blocking mechanism temporarily, always set it back to what it was afterwards. 2. Disallow callers from setting a timeout of "0", which means Non-blocking mode. This is going to create more weird problems than anybody wants, so just forbid it. I opt not to coerce '0' to 'None' to maintain the principal of least surprise in mirroring the semantics of Python's interface. Signed-off-by: John Snow <jsnow@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com> Message-id: 20201009175123.249009-4-jsnow@redhat.com Signed-off-by: John Snow <jsnow@redhat.com>
Diffstat (limited to 'python')
-rw-r--r--python/qemu/qmp.py23
1 files changed, 17 insertions, 6 deletions
diff --git a/python/qemu/qmp.py b/python/qemu/qmp.py
index 96456f7..2cd4d43 100644
--- a/python/qemu/qmp.py
+++ b/python/qemu/qmp.py
@@ -164,8 +164,11 @@ class QEMUMonitorProtocol:
retrieved or if some other error occurred.
"""
+ # Current timeout and blocking status
+ current_timeout = self.__sock.gettimeout()
+
# Check for new events regardless and pull them into the cache:
- self.__sock.setblocking(False)
+ self.__sock.settimeout(0) # i.e. setblocking(False)
try:
self.__json_read()
except OSError as err:
@@ -173,7 +176,7 @@ class QEMUMonitorProtocol:
if err.errno != errno.EAGAIN:
raise
finally:
- self.__sock.setblocking(True)
+ self.__sock.settimeout(current_timeout)
# Wait for new events, if needed.
# if wait is 0.0, this means "no wait" and is also implicitly false.
@@ -187,9 +190,11 @@ class QEMUMonitorProtocol:
except Exception as err:
msg = "Error while reading from socket"
raise QMPConnectError(msg) from err
+ finally:
+ self.__sock.settimeout(current_timeout)
+
if ret is None:
raise QMPConnectError("Error while reading from socket")
- self.__sock.settimeout(None)
def __enter__(self) -> 'QEMUMonitorProtocol':
# Implement context manager enter function.
@@ -219,7 +224,7 @@ class QEMUMonitorProtocol:
return self.__negotiate_capabilities()
return None
- def accept(self, timeout: float = 15.0) -> QMPMessage:
+ def accept(self, timeout: Optional[float] = 15.0) -> QMPMessage:
"""
Await connection from QMP Monitor and perform capabilities negotiation.
@@ -338,13 +343,19 @@ class QEMUMonitorProtocol:
if self.__sockfile:
self.__sockfile.close()
- def settimeout(self, timeout: float) -> None:
+ def settimeout(self, timeout: Optional[float]) -> None:
"""
Set the socket timeout.
- @param timeout (float): timeout in seconds, or None.
+ @param timeout (float): timeout in seconds (non-zero), or None.
@note This is a wrap around socket.settimeout
+
+ @raise ValueError: if timeout was set to 0.
"""
+ if timeout == 0:
+ msg = "timeout cannot be 0; this engages non-blocking mode."
+ msg += " Use 'None' instead to disable timeouts."
+ raise ValueError(msg)
self.__sock.settimeout(timeout)
def get_sock_fd(self) -> int: