From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5845B60A260E for ; Mon, 26 Oct 2026 11:30:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=KFLAmSe8 Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1xLIuD-000842-Ke; Mon, 26 Oct 2026 07:30:21 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xLIuA-00083N-Sf for qemu-devel@nongnu.org; Mon, 26 Oct 2026 07:30:18 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xLIu8-0001IP-3U for qemu-devel@nongnu.org; Mon, 26 Oct 2026 07:30:18 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1793014214; 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=xBec8mRSRg053NN56cKqOhLcYou/rJlajMQ/Zuc+KxU=; b=KFLAmSe8XAA1qaSL4CTBBPrje3IPtDFfr1MvX2iQKNj/UblonitVQ9yKmeM0jPGysRzBrx 9TwAoQbdbpYCYMPoeBsPNnng/2kHDDzFSVtsEcicTAxGvVL2+6rSapE0sdBskcJyxg/awg dOEDIFlQdfGMUkupJRumyyweZiGULj8= Received: from mx-prod-mc-05.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-224-A_XJTYmtO_WvYyQYVMq3Eg-1; Mon, 26 Oct 2026 07:30:04 -0400 X-MC-Unique: A_XJTYmtO_WvYyQYVMq3Eg-1 X-Mimecast-MFC-AGG-ID: A_XJTYmtO_WvYyQYVMq3Eg_1793014203 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3122419560BD; Mon, 26 Oct 2026 11:30:03 +0000 (UTC) Received: from redhat.com (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 9EC6A18004D2; Mon, 26 Oct 2026 11:29:59 +0000 (UTC) Date: Mon, 26 Oct 2026 11:29:56 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Tim Pambor Cc: qemu-devel@nongnu.org, "Michael S. Tsirkin" , Stefano Garzarella , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Paolo Bonzini , Kevin Wolf , Hanna Reitz , Jason Wang , Pierrick Bouvier , qemu-block@nongnu.org, Raphael Norwitz , Brad Smith Subject: Re: [PATCH 3/8] io/channel-socket: only clear O_NONBLOCK on received fds if set Message-ID: References: <20261022-vhost-user-posix-v1-0-0bd4d450d23c@gmail.com> <20261022-vhost-user-posix-v1-3-0bd4d450d23c@gmail.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20261022-vhost-user-posix-v1-3-0bd4d450d23c@gmail.com> User-Agent: Mutt/2.4.2 (2026-08-30) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 2 X-Spam_score: 0.2 X-Spam_bar: / X-Spam_report: (0.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.339, 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org X-Spam-Status: No, score=-17.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Thu, Oct 22, 2026 at 03:47:24PM +0200, Tim Pambor wrote: > After receiving descriptors with SCM_RIGHTS the socket channel resets > O_NONBLOCK on each of them with fcntl(F_SETFL). macOS rejects F_SETFL > on POSIX shared memory descriptors, so every message carrying such a > descriptor caused the connection to drop. Those descriptors are passed > in blocking mode anyway, so there is nothing to change on them. Query > the flags with F_GETFL first and only issue F_SETFL when O_NONBLOCK is > actually set. > > Signed-off-by: Tim Pambor > --- > io/channel-socket.c | 19 +++++++++++++++++-- > 1 file changed, 17 insertions(+), 2 deletions(-) > > diff --git a/io/channel-socket.c b/io/channel-socket.c > index 7920cee639..1785fd5bfe 100644 > --- a/io/channel-socket.c > +++ b/io/channel-socket.c > @@ -520,8 +520,23 @@ static bool qio_channel_handle_fds(int *fds, size_t nfds, > } > > if (!preserve_blocking) { > - /* O_NONBLOCK is preserved across SCM_RIGHTS so reset it */ > - if (!qemu_set_blocking(*fd, true, errp)) { > + /* > + * O_NONBLOCK is preserved across SCM_RIGHTS so reset it. > + * > + * Some descriptors reject F_SETFL outright, e.g. POSIX > + * shared memory on macOS. They are passed in blocking > + * mode anyway, so only touch descriptors that have it set. > + */ > + int flags = fcntl(*fd, F_GETFL); > + > + if (flags < 0) { > + error_setg_errno(errp, errno, > + "Can't get file descriptor %d flags", *fd); > + return false; > + } > + > + if ((flags & O_NONBLOCK) && > + !qemu_set_blocking(*fd, true, errp)) { I'd be inclined to put this logic in qemu_set_blocking itself so that it does the right thing for all possible callers. At that point we might as well get rid of the use of g_unix_set_fd_nonblocking in that function and directly call fcntl so we avoid the duplicate F_GETFL calls, eg something more like: int flags, newflags; flag = fcntl(fd, F_GETFL); if (flags < 0) { error_setg_errno(....) return -1; } if (nonblock) newflags = flags | O_NONBLOCK; else newflags = flags & ~O_NONBLOCK; if (newflags != flags && fcntl(fd, F_SETFL, newflags) < 0) { error_setg_errno(...); return -1; } With regards, Daniel -- |: https://berrange.com ~~ https://hachyderm.io/@berrange :| |: https://libvirt.org ~~ https://entangle-photo.org :| |: https://pixelfed.art/berrange ~~ https://fstop138.berrange.com :|