From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:46248) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ghdP0-0002ct-RW for qemu-devel@nongnu.org; Thu, 10 Jan 2019 11:41:56 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ghdOy-0002m1-VJ for qemu-devel@nongnu.org; Thu, 10 Jan 2019 11:41:54 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58170) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ghdOw-0002fY-Qk for qemu-devel@nongnu.org; Thu, 10 Jan 2019 11:41:52 -0500 Date: Thu, 10 Jan 2019 16:41:25 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Message-ID: <20190110164125.GS2178@redhat.com> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <20190109112728.9214-1-xieyongji@baidu.com> <20190109112728.9214-2-xieyongji@baidu.com> <20190110124946.GL2178@redhat.com> <20190110132443.GM2178@redhat.com> <20190110141125.GP2178@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v4 for-4.0 1/7] char-socket: Enable "nowait" option on client sockets List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Yongji Xie Cc: "Michael S. Tsirkin" , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Jason Wang , "Coquelin, Maxime" , Yury Kotov , =?utf-8?B?0JXQstCz0LXQvdC40Lkg0K/QutC+0LLQu9C10LI=?= , qemu-devel , zhangyu31@baidu.com, chaiwen@baidu.com, nixun@baidu.com, lilin24@baidu.com, Xie Yongji On Thu, Jan 10, 2019 at 10:29:20PM +0800, Yongji Xie wrote: > On Thu, 10 Jan 2019 at 22:11, Daniel P. Berrang=C3=A9 wrote: > > > > On Thu, Jan 10, 2019 at 10:08:54PM +0800, Yongji Xie wrote: > > > On Thu, 10 Jan 2019 at 21:24, Daniel P. Berrang=C3=A9 wrote: > > > > > > > > On Thu, Jan 10, 2019 at 09:19:41PM +0800, Yongji Xie wrote: > > > > > On Thu, 10 Jan 2019 at 20:50, Daniel P. Berrang=C3=A9 wrote: > > > > > > > > > > > > On Wed, Jan 09, 2019 at 07:27:22PM +0800, elohimes@gmail.com = wrote: > > > > > > > From: Xie Yongji > > > > > > > > > > > > > > Enable "nowait" option to make QEMU not do a connect > > > > > > > on client sockets during initialization of the chardev. > > > > > > > Then we can use qemu_chr_fe_wait_connected() to connect > > > > > > > when necessary. Now it would be used for unix domain > > > > > > > socket of vhost-user-blk device to support reconnect. > > > > > > > > > > > > > > Signed-off-by: Xie Yongji > > > > > > > Signed-off-by: Zhang Yu > > > > > > > --- > > > > > > > chardev/char-socket.c | 56 +++++++++++++++++++++----------= ------------ > > > > > > > qapi/char.json | 3 +-- > > > > > > > qemu-options.hx | 9 ++++--- > > > > > > > 3 files changed, 35 insertions(+), 33 deletions(-) > > > > > > > > > > > > > > diff --git a/chardev/char-socket.c b/chardev/char-socket.c > > > > > > > index eaa8e8b68f..f803f4f7d3 100644 > > > > > > > --- a/chardev/char-socket.c > > > > > > > +++ b/chardev/char-socket.c > > > > > > > @@ -1072,37 +1072,37 @@ static void qmp_chardev_open_socket= (Chardev *chr, > > > > > > > s->reconnect_time =3D reconnect; > > > > > > > } > > > > > > > > > > > > > > - if (s->reconnect_time) { > > > > > > > - tcp_chr_connect_async(chr); > > > > > > > - } else { > > > > > > > - if (s->is_listen) { > > > > > > > - char *name; > > > > > > > - s->listener =3D qio_net_listener_new(); > > > > > > > + if (s->is_listen) { > > > > > > > + char *name; > > > > > > > + s->listener =3D qio_net_listener_new(); > > > > > > > > > > > > > > - name =3D g_strdup_printf("chardev-tcp-listener= -%s", chr->label); > > > > > > > - qio_net_listener_set_name(s->listener, name); > > > > > > > - g_free(name); > > > > > > > + name =3D g_strdup_printf("chardev-tcp-listener-%s"= , chr->label); > > > > > > > + qio_net_listener_set_name(s->listener, name); > > > > > > > + g_free(name); > > > > > > > > > > > > > > - if (qio_net_listener_open_sync(s->listener, s-= >addr, errp) < 0) { > > > > > > > - object_unref(OBJECT(s->listener)); > > > > > > > - s->listener =3D NULL; > > > > > > > - goto error; > > > > > > > - } > > > > > > > + if (qio_net_listener_open_sync(s->listener, s->add= r, errp) < 0) { > > > > > > > + object_unref(OBJECT(s->listener)); > > > > > > > + s->listener =3D NULL; > > > > > > > + goto error; > > > > > > > + } > > > > > > > > > > > > > > - qapi_free_SocketAddress(s->addr); > > > > > > > - s->addr =3D socket_local_address(s->listener->= sioc[0]->fd, errp); > > > > > > > - update_disconnected_filename(s); > > > > > > > + qapi_free_SocketAddress(s->addr); > > > > > > > + s->addr =3D socket_local_address(s->listener->sioc= [0]->fd, errp); > > > > > > > + update_disconnected_filename(s); > > > > > > > > > > > > > > - if (is_waitconnect && > > > > > > > - qemu_chr_wait_connected(chr, errp) < 0) { > > > > > > > - return; > > > > > > > - } > > > > > > > - if (!s->ioc) { > > > > > > > - qio_net_listener_set_client_func_full(s->l= istener, > > > > > > > - tcp_= chr_accept, > > > > > > > - chr,= NULL, > > > > > > > - chr-= >gcontext); > > > > > > > - } > > > > > > > + if (is_waitconnect && > > > > > > > + qemu_chr_wait_connected(chr, errp) < 0) { > > > > > > > + return; > > > > > > > + } > > > > > > > + if (!s->ioc) { > > > > > > > + qio_net_listener_set_client_func_full(s->liste= ner, > > > > > > > + tcp_chr_= accept, > > > > > > > + chr, NUL= L, > > > > > > > + chr->gco= ntext); > > > > > > > + } > > > > > > > + } else if (is_waitconnect) { > > > > > > > + if (s->reconnect_time) { > > > > > > > + tcp_chr_connect_async(chr); > > > > > > > } else if (qemu_chr_wait_connected(chr, errp) < 0)= { > > > > > > > goto error; > > > > > > > } > > > > > > > > > > > > This skips everything when 'is_waitconnect' is false. > > > > > > > > > > > > This combines with a bug in tests/libqtest.c which adds the '= nowait' > > > > > > flag to the -chardevs it cteates. This mistake was previously= ignored > > > > > > because the chardevs were socket clients, but now we honour i= t. > > > > > > > > > > > > We shoul remove 'nowait' from the qtest chardevs, but separat= ely > > > > > > from that this code should also still attempt a non-blocking > > > > > > connect when is_waitconnect is false. > > > > > > > > > > > > > > > > Do you mean we still need to connect server in background with > > > > > "nowait" option? But my purpose is not to connect server until = we > > > > > manually call qemu_chr_fe_wait_connected() in other place. > > > > > > > > I don't see a need to delay the connect. We can start a > > > > background connect right away. The later code you have > > > > merely needs to wait for that background connect to > > > > finish, which qemu_chr_fe_wait_connected still accomplishes. > > > > This keeps the chardev code clearer only having 2 distinct > > > > code paths to worry about - blocking or non-blocking connect. > > > > > > > > > > Now the problem is that we have a server that only accept one > > > connection. And we want to read something from it during device > > > initializtion. > > > > > > If background connect it before we call qemu_chr_fe_wait_connected(= ) > > > during device initializtion, qemu_chr_fe_wait_connected() will > > > accomplish but we can't read anything. And we have no way to releas= e > > > the background connection. So what I want to do in this patch is to > > > disable background connect. > > > > I'm not seeing the problem here. What I proposed results in > > > > 1. chardev starts connect() >=20 > This should be asynchronous with "reconnect" option. Another thread > may connect before vhost backend? >=20 > > 2. vhost backend waits for connect() to complete >=20 > Sorry, I'm not sure I get your point here. Do you mean vhost backend > call qemu_chr_fe_wait_connected()? Seems like > qemu_chr_fe_wait_connected() will connect directly rather than wait > for connect() to complete? Ahhhh, yes, you are right. qemu_chr_fe_wait_connected will potentially cause a second connection to be established Looking at it the qemu_chr_fe_wait_connected() I believe it is seriously broken even before this patch series. The intended usage is that a device can all qemu_chr_fe_wait_connected to wait for a new connection to be established, and then do I/O on the chardev. This does not in fact work if TLS, websock or telnet modes are enabled for the socket, due to a mistake introduced when we previousl= y tried to fix this: commit 1dc8a6695c731abb7461c637b2512c3670d82be4 Author: Marc-Andr=C3=A9 Lureau Date: Tue Aug 16 12:33:32 2016 +0400 char: fix waiting for TLS and telnet connection That commit fixed the problem where we continued to accept() new sockets when TLS/telnet was enabled, because the 's->connected' flag isn't set immediately. Unfortunately what this means is that when qemu_chr_fe_wait_connected returns, the chardev is *not* ready to read/write data. The TLS/telnet handshake has not been run, and is still pending in the background. So we'll end up with device backend trying todo I/O on the chardev at the same time as it is trying todo the TLS/telnet handshake. We need to fix qemu_chr_fe_wait_connected so that it does explicit synchronization wrt to any ongoing background connection process. It must only return once all TLS/telnet/websock handshakes have completed. If we fix that correctly, then I believe it will also solve the problem you're trying to address. Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberran= ge :| |: https://libvirt.org -o- https://fstop138.berrange.c= om :| |: https://entangle-photo.org -o- https://www.instagram.com/dberran= ge :|