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=-11.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 C3785C433DF for ; Mon, 20 Jul 2020 18:31:00 +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 55760208E4 for ; Mon, 20 Jul 2020 18:31:00 +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="eIvbjWnm" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 55760208E4 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]:56586 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jxaZ1-00084B-AX for qemu-devel@archiver.kernel.org; Mon, 20 Jul 2020 14:30:59 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35666) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jxaXn-0007SZ-1k for qemu-devel@nongnu.org; Mon, 20 Jul 2020 14:29:43 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:26943 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jxaXk-0004jU-3O for qemu-devel@nongnu.org; Mon, 20 Jul 2020 14:29:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1595269778; 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=ESC7lHJZEWU8baXjgzf9kEzpgGoBQTa40Od5KbPxuos=; b=eIvbjWnmD1GAuxLGkDV3npdE6jxhERBbK+ALWv3lPT1WpgkASDYNaxbCDNxI+SiPPSQG1y VkhGMoOU72Kn1/TelIHDH/Va3XjvomshEJ+iO/Ed4nW1TGDpxlIyd9SQSxEyJV4hvH5jD5 T9rnCwdb0Bjmuol4PD2n4lzT3X57XG8= 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-469-SXBfPDZ0NICzTifIysEbYQ-1; Mon, 20 Jul 2020 14:29:33 -0400 X-MC-Unique: SXBfPDZ0NICzTifIysEbYQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0C95C8015F3; Mon, 20 Jul 2020 18:29:32 +0000 (UTC) Received: from redhat.com (unknown [10.36.110.53]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 187B45D9D5; Mon, 20 Jul 2020 18:29:25 +0000 (UTC) Date: Mon, 20 Jul 2020 19:29:23 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Vladimir Sementsov-Ogievskiy Subject: Re: [PATCH 3/4] io/channel-socket: implement non-blocking connect Message-ID: <20200720182923.GP643836@redhat.com> References: <20200720180715.10521-1-vsementsov@virtuozzo.com> <20200720180715.10521-4-vsementsov@virtuozzo.com> MIME-Version: 1.0 In-Reply-To: <20200720180715.10521-4-vsementsov@virtuozzo.com> User-Agent: Mutt/1.14.5 (2020-06-23) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 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=207.211.31.81; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/19 21:45:06 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: kwolf@redhat.com, qemu-block@nongnu.org, qemu-devel@nongnu.org, mreitz@redhat.com, kraxel@redhat.com, den@openvz.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, Jul 20, 2020 at 09:07:14PM +0300, Vladimir Sementsov-Ogievskiy wrote: > Utilize new socket API to make a non-blocking connect for inet sockets. > > Signed-off-by: Vladimir Sementsov-Ogievskiy > --- > include/io/channel-socket.h | 14 +++++++ > io/channel-socket.c | 74 +++++++++++++++++++++++++++++++++++++ > 2 files changed, 88 insertions(+) > > diff --git a/include/io/channel-socket.h b/include/io/channel-socket.h > index 777ff5954e..82e868bc02 100644 > --- a/include/io/channel-socket.h > +++ b/include/io/channel-socket.h > @@ -94,6 +94,20 @@ int qio_channel_socket_connect_sync(QIOChannelSocket *ioc, > SocketAddress *addr, > Error **errp); > > +/** > + * qio_channel_socket_connect_non_blocking_sync: > + * @ioc: the socket channel object > + * @addr: the address to connect to > + * @errp: pointer to a NULL-initialized error object > + * > + * Attempt to connect to the address @addr using non-blocking mode of > + * the socket. Function is synchronous, but being called from > + * coroutine context will yield during connect operation. > + */ > +int qio_channel_socket_connect_non_blocking_sync(QIOChannelSocket *ioc, > + SocketAddress *addr, > + Error **errp); > + > /** > * qio_channel_socket_connect_async: > * @ioc: the socket channel object > diff --git a/io/channel-socket.c b/io/channel-socket.c > index e1b4667087..076de7578a 100644 > --- a/io/channel-socket.c > +++ b/io/channel-socket.c > @@ -22,6 +22,7 @@ > #include "qapi/error.h" > #include "qapi/qapi-visit-sockets.h" > #include "qemu/module.h" > +#include "qemu/sockets.h" > #include "io/channel-socket.h" > #include "io/channel-watch.h" > #include "trace.h" > @@ -29,6 +30,8 @@ > > #define SOCKET_MAX_FDS 16 > > +static int qio_channel_socket_close(QIOChannel *ioc, Error **errp); > + > SocketAddress * > qio_channel_socket_get_local_address(QIOChannelSocket *ioc, > Error **errp) > @@ -157,6 +160,77 @@ int qio_channel_socket_connect_sync(QIOChannelSocket *ioc, > return 0; > } > > +static int qio_channel_inet_connect_non_blocking_sync(QIOChannelSocket *ioc, > + InetSocketAddress *addr, Error **errp) > +{ > + Error *local_err = NULL; > + struct addrinfo *infos, *info; > + int sock = -1; > + > + infos = inet_parse_connect_saddr(addr, errp); > + if (!infos) { > + return -1; > + } This call is blocking since it calls getaddrinfo whose design offers no ability todo non-blocking DNS lookups. Given this call, ... > + > + for (info = infos; info != NULL; info = info->ai_next) { > + bool in_progress; > + > + error_free(local_err); > + local_err = NULL; > + > + sock = inet_connect_addr(addr, info, false, &in_progress, &local_err); > + if (sock < 0) { > + continue; > + } > + > + if (qio_channel_socket_set_fd(ioc, sock, &local_err) < 0) { > + close(sock); > + continue; > + } > + > + if (in_progress) { > + if (qemu_in_coroutine()) { > + qio_channel_yield(QIO_CHANNEL(ioc), G_IO_OUT); > + } else { > + qio_channel_wait(QIO_CHANNEL(ioc), G_IO_OUT); > + } ...this is offering false assurances of being non-blocking. If we don't want the current thread to be blocked then we need to be using the existing qio_channel_socket_connect_async method or similar. It uses a throw away background thread to run the connection attempt, and then reports completion back later, thus avoiding the getaddrinfo design flaw for the callers. I explicitly didn't want to add an method like the impl in this patch, because getaddrinfo dooms it and we already had bugs in the pre-QIOChannel code where QEMU thought it was non-blocking but wasn't due to getaddrinfo lookups. IIUC, the main appeal of this method is that the non-blocking nature is hidden from the caller who can continue to treat it as a synchronous call and have the coroutine magic happen in behind the scenes. IOW, What's needed is a simple way to run the operation in a thread, and sleep for completion while having the coroutine yield. I think this could likely be achieved with QIOTask with an alternate impl of the qio_task_wait_thread() method that is friendly to coroutines instead of being based on pthread condition variable waits. > + if (socket_check(sock, &local_err) < 0) { > + qio_channel_socket_close(QIO_CHANNEL(ioc), NULL); > + continue; > + } > + } > + > + break; > + } > + > + freeaddrinfo(infos); > + > + error_propagate(errp, local_err); > + return sock; > +} 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 :|