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Tue, 20 Oct 2020 17:28:14 +0000 (UTC) Received: from scv.redhat.com (ovpn-115-172.rdu2.redhat.com [10.10.115.172]) by smtp.corp.redhat.com (Postfix) with ESMTP id 098E71992D; Tue, 20 Oct 2020 17:28:12 +0000 (UTC) From: John Snow To: qemu-devel@nongnu.org Subject: [PULL 21/21] python/qemu/qmp.py: Fix settimeout operation Date: Tue, 20 Oct 2020 13:27:42 -0400 Message-Id: <20201020172742.1483258-22-jsnow@redhat.com> In-Reply-To: <20201020172742.1483258-1-jsnow@redhat.com> References: <20201020172742.1483258-1-jsnow@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jsnow@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=63.128.21.124; envelope-from=jsnow@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/20 01:15:43 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Peter Maydell , Eduardo Habkost , qemu-block@nongnu.org, =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , Max Reitz , Cleber Rosa , John Snow Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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 Reviewed-by: Philippe Mathieu-Daudé Message-id: 20201009175123.249009-4-jsnow@redhat.com Signed-off-by: John Snow --- python/qemu/qmp.py | 23 +++++++++++++++++------ 1 file changed, 17 insertions(+), 6 deletions(-) diff --git a/python/qemu/qmp.py b/python/qemu/qmp.py index 4969e5741c..f64517fb0a 100644 --- a/python/qemu/qmp.py +++ b/python/qemu/qmp.py @@ -164,16 +164,19 @@ def __get_events(self, wait: Union[bool, float] = False) -> None: 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: try: - self.__sock.setblocking(False) + self.__sock.settimeout(0) # i.e. setblocking(False) self.__json_read() except OSError as err: # EAGAIN: No data available; not critical 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 @@ def __get_events(self, wait: Union[bool, float] = False) -> None: 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 @@ def connect(self, negotiate: bool = True) -> Optional[QMPMessage]: 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 @@ def close(self) -> None: 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: