From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2D480C4363A for ; Tue, 20 Oct 2020 19:08:14 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4F6AF2224A for ; Tue, 20 Oct 2020 19:08:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="bZnPQVcE" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4F6AF2224A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:51854 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kUwzU-00045o-16 for qemu-devel@archiver.kernel.org; Tue, 20 Oct 2020 15:08:12 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35156) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kUwyP-0003aQ-Gt for qemu-devel@nongnu.org; Tue, 20 Oct 2020 15:07:06 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:56795) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kUwyL-0005l7-EM for qemu-devel@nongnu.org; Tue, 20 Oct 2020 15:07:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1603220820; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ROCWlIJvRB6Bs3cqTpEsL6Ka3QQpKYW9nJlBLfPEWsc=; b=bZnPQVcEAUAFy+aK03Gbo3Yb2Pj4ivxFWA4CMK6Tf3f6i5gwIdBSQyMIBH+IhyrIxkh+gT ErR153rCKIN1m7y1BSII3v2zcfeyJZ/DwgEXlYne0eem/QcTSopRMYjLgzPondeHxXirFM HspteUWRgmYT3XdKiK6s3jnd1ZNEEoA= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-164-FK2T3Fs8PuScfhR5NaILKg-1; Tue, 20 Oct 2020 15:06:57 -0400 X-MC-Unique: FK2T3Fs8PuScfhR5NaILKg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 43CE41868434; Tue, 20 Oct 2020 19:06:56 +0000 (UTC) Received: from [10.10.115.172] (ovpn-115-172.rdu2.redhat.com [10.10.115.172]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1A03860C0F; Tue, 20 Oct 2020 19:06:46 +0000 (UTC) Subject: Re: [PULL 20/21] python/qemu/qmp.py: re-raise OSError when encountered To: Nir Soffer References: <20201020172742.1483258-1-jsnow@redhat.com> <20201020172742.1483258-21-jsnow@redhat.com> From: John Snow Message-ID: <3a096ef6-36a3-73ac-e0e8-90a3c4473b5d@redhat.com> Date: Tue, 20 Oct 2020 15:06:45 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 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 Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit 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, NICE_REPLY_A=-0.001, 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=unavailable 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 , QEMU Developers , Max Reitz , Cleber Rosa , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 10/20/20 2:15 PM, Nir Soffer wrote: > On Tue, Oct 20, 2020 at 8:52 PM John Snow wrote: >> >> Nested if conditions don't change when the exception block fires; we >> need to explicitly re-raise the error if we didn't intend to capture and >> suppress it. >> >> Signed-off-by: John Snow >> Reviewed-by: Philippe Mathieu-Daudé >> Message-id: 20201009175123.249009-3-jsnow@redhat.com >> Signed-off-by: John Snow >> --- >> python/qemu/qmp.py | 11 ++++++----- >> 1 file changed, 6 insertions(+), 5 deletions(-) >> >> diff --git a/python/qemu/qmp.py b/python/qemu/qmp.py >> index d911999da1..4969e5741c 100644 >> --- a/python/qemu/qmp.py >> +++ b/python/qemu/qmp.py >> @@ -165,14 +165,15 @@ def __get_events(self, wait: Union[bool, float] = False) -> None: >> """ >> >> # Check for new events regardless and pull them into the cache: >> - self.__sock.setblocking(False) >> try: >> + self.__sock.setblocking(False) > > This change is not required. The idiom is: > > do stuff > try: > something > finally: > undo stuff > > If do stuff failed, there is no need to undo it. > > socket.setblocking() should not fail with EAGAIN, so it > does not need to be inside the try block. > Squashing this change in, will send a new V2 cover letter. >> self.__json_read() >> except OSError as err: >> - if err.errno == errno.EAGAIN: >> - # No data available >> - pass >> - self.__sock.setblocking(True) >> + # EAGAIN: No data available; not critical >> + if err.errno != errno.EAGAIN: >> + raise > > In python 3 this can be simplified to: > > try: > self.__json_read() > except BlockingIOError: > pass > > https://docs.python.org/3.6/library/exceptions.html#BlockingIOError > I'm a lot less clear on this. We only check for EAGAIN, but that would check for EAGAIN, EALREADY, EWOULDBLOCK and EINPROGRESS. That's probably fine, really, but: There is something worse lurking in the code here too, and I really didn't want to get into it on this series, but we are making use of undefined behavior (sockfile.readline() on a non-blocking socket) -- It seems to work in practice so far, but it's begging to break. For that reason (This code should never have worked anyway), I am extremely reluctant to change the exception classes we catch here until we fix the problem. --js >> + finally: >> + self.__sock.setblocking(True) >> >> # Wait for new events, if needed. >> # if wait is 0.0, this means "no wait" and is also implicitly false. >> -- >> 2.26.2 > > Nir >