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[10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9518980484C; Tue, 14 Jul 2020 18:47:35 +0000 (UTC) Received: from [10.10.113.141] (ovpn-113-141.rdu2.redhat.com [10.10.113.141]) by smtp.corp.redhat.com (Postfix) with ESMTP id CD3AA390; Tue, 14 Jul 2020 18:47:31 +0000 (UTC) Subject: Re: [PATCH v5 05/12] python/machine.py: Prohibit multiple shutdown() calls To: Cleber Rosa References: <20200710050649.32434-1-jsnow@redhat.com> <20200710050649.32434-6-jsnow@redhat.com> <20200714024858.GA2983508@localhost.localdomain> From: John Snow Autocrypt: addr=jsnow@redhat.com; prefer-encrypt=mutual; keydata= mQINBFTKefwBEAChvwqYC6saTzawbih87LqBYq0d5A8jXYXaiFMV/EvMSDqqY4EY6whXliNO IYzhgrPEe7ZmPxbCSe4iMykjhwMh5byIHDoPGDU+FsQty2KXuoxto+ZdrP9gymAgmyqdk3aV vzzmCa3cOppcqKvA0Kqr10UeX/z4OMVV390V+DVWUvzXpda45/Sxup57pk+hyY52wxxjIqef 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[generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, 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_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=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: kwolf@redhat.com, Aleksandar Rikalo , Eduardo Habkost , qemu-devel@nongnu.org, Wainer dos Santos Moschetta , Aleksandar Markovic , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , Aurelien Jarno Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 7/13/20 10:48 PM, Cleber Rosa wrote: > On Fri, Jul 10, 2020 at 01:06:42AM -0400, John Snow wrote: >> If the VM is not launched, don't try to shut it down. As a change, >> _post_shutdown now unconditionally also calls _early_cleanup in order to >> offer comprehensive object cleanup in failure cases. >> >> As a courtesy, treat it as a NOP instead of rejecting it as an >> error. This is slightly nicer for acceptance tests where vm.shutdown() >> is issued unconditionally in tearDown callbacks. >> >> Signed-off-by: John Snow >> --- >> python/qemu/machine.py | 14 +++++++++++++- >> 1 file changed, 13 insertions(+), 1 deletion(-) >> >> diff --git a/python/qemu/machine.py b/python/qemu/machine.py >> index cac466fbe6..e66a7d66dd 100644 >> --- a/python/qemu/machine.py >> +++ b/python/qemu/machine.py >> @@ -283,6 +283,13 @@ def _post_launch(self): >> self._qmp.accept() >> >> def _post_shutdown(self): >> + """ >> + Called to cleanup the VM instance after the process has exited. >> + May also be called after a failed launch. >> + """ >> + # Comprehensive reset for the failed launch case: >> + self._early_cleanup() >> + > > I'm not following why this is needed here. AFAICT, the closing of the > console socket file was introduced when the QEMU process was alive, > and doing I/O on the serial device attached to the console file (and > was only necessary because of that). In those scenarios, a race > between the time of sending the QMP command to quit, and getting a > response from QMP could occur. > > But here, IIUC, there's no expectations for the QEMU process to be alive. > To the best of my understanding and testing, this line did not contribute > to the robustness of the shutdown behavior. > > Finally, given that currently, only the closing of the console socket > is done within _early_cleanup(), and that is conditional, this also does > no harm AFAICT. If more early cleanups operations were needed, then I > would feel less bothered about calling it here. > >> if self._qmp: >> self._qmp.close() >> self._qmp = None >> @@ -328,7 +335,7 @@ def launch(self): >> self._launch() >> self._launched = True >> except: >> - self.shutdown() >> + self._post_shutdown() >> >> LOG.debug('Error launching VM') >> if self._qemu_full_args: >> @@ -357,6 +364,8 @@ def _launch(self): >> def _early_cleanup(self) -> None: >> """ >> Perform any cleanup that needs to happen before the VM exits. >> + >> + Called additionally by _post_shutdown for comprehensive cleanup. >> """ >> # If we keep the console socket open, we may deadlock waiting >> # for QEMU to exit, while QEMU is waiting for the socket to >> @@ -377,6 +386,9 @@ def shutdown(self, has_quit=False, hard=False): >> """ >> Terminate the VM and clean up >> """ >> + if not self._launched: >> + return >> + > > Because of the additional logic, it'd be a good opportunity to make > the docstring more accurate. This method may now *not* do *any* of if > termination and cleaning (while previously it would attempt those > anyhow). > The docstring gets hit with a polish beam later in the series, but still neglects that it might do nothing. I squashed in a change to patch #10 and pushed to my gitlab to add this clarification to the docstring. https://gitlab.com/jsnow/qemu/-/tree/python-package-shutdown https://gitlab.com/jsnow/qemu/-/commit/b3f14deb730fda9bb2a28a9366a8096d3617f4f4