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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 841DEC02185 for ; Wed, 15 Jan 2025 10:40:00 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tY0np-0007xq-Bv; Wed, 15 Jan 2025 05:39:13 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tY0nm-0007xa-Ha for qemu-devel@nongnu.org; Wed, 15 Jan 2025 05:39:11 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tY0nk-00050Q-FP for qemu-devel@nongnu.org; Wed, 15 Jan 2025 05:39:10 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1736937545; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Ai2W8Cm2E/I+HcL/Seu+PjoXIofaesCZk0zlrmAtj4Y=; b=g6PL/JaiP/D+ZtnrcOYVB6/JXFaWmbjSQQITA2hXXwkL4VV11bZglS1+07T9OWrmnt4/Fu Z4+a8DEFV7YJNjuDtX96BVH474yG438lMVB1qD6elR3W9fFGWwlqvV6/+RCgymao+2GUw1 fZXhRawYcPCZgAiq1RYXfkC92CboEiQ= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-487-5buwi3YWMDiRJJR5ALFnHw-1; Wed, 15 Jan 2025 05:38:59 -0500 X-MC-Unique: 5buwi3YWMDiRJJR5ALFnHw-1 X-Mimecast-MFC-AGG-ID: 5buwi3YWMDiRJJR5ALFnHw Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C4AE21955E7F; Wed, 15 Jan 2025 10:38:58 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.126]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0AA2230001BE; Wed, 15 Jan 2025 10:38:56 +0000 (UTC) Date: Wed, 15 Jan 2025 10:38:53 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Akihiko Odaki Cc: Jason Wang , qemu-devel@nongnu.org, devel@daynix.com Subject: Re: [PATCH v2 2/2] tap: Use g_spawn_sync() and g_spawn_check_wait_status() Message-ID: References: <20250104-glib-v2-0-12013f3e5782@daynix.com> <20250104-glib-v2-2-12013f3e5782@daynix.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.13 (2024-03-09) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.063, 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_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, Jan 15, 2025 at 03:04:19PM +0900, Akihiko Odaki wrote: > On 2025/01/06 18:34, Daniel P. Berrangé wrote: > > On Sat, Jan 04, 2025 at 05:04:08PM +0900, Akihiko Odaki wrote: > > > g_spawn_sync() gives an informative message if it fails to execute > > > the script instead of reporting exiting status 1. > > > > > > g_spawn_check_wait_status() also gives an message easier to understand > > > than the raw value returned by waitpid(). > > > > > > Signed-off-by: Akihiko Odaki > > > --- > > > net/tap.c | 169 ++++++++++++++++++++++++-------------------------------------- > > > 1 file changed, 66 insertions(+), 103 deletions(-) > > > > > > diff --git a/net/tap.c b/net/tap.c > > > index ae1c7e398321..392a024f8ed9 100644 > > > --- a/net/tap.c > > > +++ b/net/tap.c > > > @@ -385,56 +385,30 @@ static TAPState *net_tap_fd_init(NetClientState *peer, > > > return s; > > > } > > > -static void close_all_fds_after_fork(int excluded_fd) > > > +static void unset_cloexec(gpointer data) > > > { > > > - const int skip_fd[] = {STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO, > > > - excluded_fd}; > > > - unsigned int nskip = ARRAY_SIZE(skip_fd); > > > - > > > - /* > > > - * skip_fd must be an ordered array of distinct fds, exclude > > > - * excluded_fd if already included in the [STDIN_FILENO - STDERR_FILENO] > > > - * range > > > - */ > > > - if (excluded_fd <= STDERR_FILENO) { > > > - nskip--; > > > - } > > > - > > > - qemu_close_all_open_fd(skip_fd, nskip); > > > + g_assert(!fcntl(GPOINTER_TO_INT(data), F_SETFD, 0)); > > > } > > > static void launch_script(const char *setup_script, const char *ifname, > > > int fd, Error **errp) > > > { > > > - int pid, status; > > > - char *args[3]; > > > - char **parg; > > > + gint status; > > > + gchar *argv[] = { (gchar *)setup_script, (gchar *)ifname, NULL }; > > > + g_autoptr(GError) error = NULL; > > > /* try to launch network script */ > > > - pid = fork(); > > > - if (pid < 0) { > > > - error_setg_errno(errp, errno, "could not launch network script %s", > > > - setup_script); > > > + if (!g_spawn_sync(NULL, argv, NULL, G_SPAWN_CHILD_INHERITS_STDIN, > > > + unset_cloexec, GINT_TO_POINTER(fd), > > > + NULL, NULL, &status, &error)) { > > > > This unset_cloexec callback is relying on knowledge of current internal > > impl details of g_spawn_sync. The API docs say that all file descriptors > > will be closed, except for stdin/out/err. We should not assume glib is > > doing this by setting O_CLOEXEC, as opposed to directly calling close(). > > > > If we need specific FDs to remain open, we neeed to be using the other > > g_spawn_async_with_pipes_and_fds API that accepts a list of FDs to remain > > open. > > g_spawn_async_with_pipes_and_fds() is not available for 2.66 so we cannot > use it. > > An upstream developer says unsetting FD_CLOEXEC in the setup function is > fine in such a scenario. They are not documenting that because new glib > versions they are developing has g_spawn_async_with_pipes_and_fds(), which > is a better alternative: > https://gitlab.gnome.org/GNOME/glib/-/merge_requests/4452 That comment only says we're fine to unset FD_CLOEXEC on *historical* releases of GLib. ie they're not going to break this in a bug fix on a stable branch of 2.66.x. For anything >= 2.68 they say we need to be using g_spawn_async_with_pipes_and_fds IOW, we need to support both code paths today, and in future when we drop 2.66 compat, we can eliminate the FD_CLOEXEC codepath, leaving us with only g_spawn_async_with_pipes_and_fds With 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 :|