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=-10.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 757DEC433B4 for ; Fri, 14 May 2021 08:19:36 +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 2C3B061451 for ; Fri, 14 May 2021 08:19:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2C3B061451 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]:51428 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lhT2l-0001wn-3C for qemu-devel@archiver.kernel.org; Fri, 14 May 2021 04:19:35 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:58392) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lhT1t-0001Fk-FY for qemu-devel@nongnu.org; Fri, 14 May 2021 04:18:41 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:35833) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lhT1r-0004S5-Su for qemu-devel@nongnu.org; Fri, 14 May 2021 04:18:41 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1620980319; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=7hHK4T7UUFzEHf+BAQsTgqxv1ZJA06N08Vh4lOBsTZE=; b=faW9atdzx0iTKxJ1yyX8xKJK/h1q75XJa2q64QRj6cyu3eF7zPldQfeWhlhotdDMm8V19a 28xoFR5PvydHWfkm97HP8q+gUnSfgywjqpxjv2pYZVZXSNSdpbE/KuNu/JYSMCWOpQZlTJ xrcRlSaLBW/5BaADZ6S/Dae8NS0qXoQ= 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-361-W9R1hnSmOuGa-jVsUBhOXw-1; Fri, 14 May 2021 04:18:31 -0400 X-MC-Unique: W9R1hnSmOuGa-jVsUBhOXw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 67D696D581; Fri, 14 May 2021 08:18:30 +0000 (UTC) Received: from redhat.com (ovpn-113-212.ams2.redhat.com [10.36.113.212]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A339663BA7; Fri, 14 May 2021 08:18:11 +0000 (UTC) Date: Fri, 14 May 2021 09:18:08 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Steven Sistare Subject: Re: [PATCH V3 06/22] vl: add helper to request re-exec Message-ID: References: <1620390320-301716-1-git-send-email-steven.sistare@oracle.com> <1620390320-301716-7-git-send-email-steven.sistare@oracle.com> <19d18308-c52c-8b87-8deb-98faecd730f6@oracle.com> MIME-Version: 1.0 In-Reply-To: <19d18308-c52c-8b87-8deb-98faecd730f6@oracle.com> User-Agent: Mutt/2.0.6 (2021-03-06) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.699, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Jason Zeng , Juan Quintela , "Michael S. Tsirkin" , qemu-devel@nongnu.org, "Dr. David Alan Gilbert" , Alex Williamson , Stefan Hajnoczi , Paolo Bonzini , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Alex =?utf-8?Q?Benn=C3=A9e?= , Markus Armbruster Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, May 13, 2021 at 04:19:22PM -0400, Steven Sistare wrote: > On 5/7/2021 10:31 AM, Eric Blake wrote: > > On 5/7/21 7:25 AM, Steve Sistare wrote: > >> Add a qemu_exec_requested() hook that causes the main loop to exit and > >> re-exec qemu using the same initial arguments. If /usr/bin/qemu-exec > >> exists, exec that instead. This is an optional site-specific trampoline > >> that may alter the environment before exec'ing the qemu binary. > >> > >> Signed-off-by: Steve Sistare > >> --- > > > >> +static void qemu_exec(void) > >> +{ > >> + const char *helper = "/usr/bin/qemu-exec"; > >> + const char *bin = !access(helper, X_OK) ? helper : argv_main[0]; > > > > Reads awkwardly; I would have used '...= access(helper, X_OK) == 0 ?...' > > Will fix. > > >> + > >> + execvp(bin, argv_main); > >> + error_report("execvp failed, errno %d.", errno); > > > > error_report should not be used with a trailing dot. > > Will fix. I was not sure because I see examples both ways, though no dot prevails. > Perhaps it should be added to the style guide and checkpatch. > > > Also, %d for errno is awkward, better is: > > > > error_report("execvp failed: %s", strerror(errno)); > > I shy away from strerror because it is not thread safe, but I see qemu uses it > extensively. Will fix. GLib provides 'g_strerror' which is threadsafe, but without the horrible API of strerror_r. It works by caching the errno strings in a static table on demand. We don't use it much in QEMU, but I think we ought to. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|