From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:43336) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TT77G-000092-Te for qemu-devel@nongnu.org; Tue, 30 Oct 2012 04:24:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TT77A-0006X7-Gq for qemu-devel@nongnu.org; Tue, 30 Oct 2012 04:24:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54352) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TT77A-0006Wx-9K for qemu-devel@nongnu.org; Tue, 30 Oct 2012 04:24:00 -0400 Received: from int-mx02.intmail.prod.int.phx2.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id q9U8Nxn3005127 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 30 Oct 2012 04:23:59 -0400 From: Juan Quintela In-Reply-To: <87y5ioh0no.fsf@blackfin.pond.sub.org> (Markus Armbruster's message of "Tue, 30 Oct 2012 08:36:11 +0100") References: <1351519903-26607-1-git-send-email-quintela@redhat.com> <1351519903-26607-8-git-send-email-quintela@redhat.com> <87objlp97t.fsf@blackfin.pond.sub.org> <87r4ohkwvj.fsf@elfo.mitica> <87y5ioh0no.fsf@blackfin.pond.sub.org> Date: Tue, 30 Oct 2012 09:23:56 +0100 Message-ID: <87d300l65f.fsf@elfo.mitica> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH 07/18] migration: make writes blocking Reply-To: quintela@redhat.com List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster Cc: owasserm@redhat.com, mtosatti@redhat.com, qemu-devel@nongnu.org, pbonzini@redhat.com, avi@redhat.com Markus Armbruster wrote: > Juan Quintela writes: > >> Markus Armbruster wrote: >>> Juan Quintela writes: >>> >>>> Move all the writes to the migration_thread, and make writings >>>> blocking. Notice that are still using the iothread for everything >>>> that we do. >>> [...] >>>> diff --git a/qemu-sockets.c b/qemu-sockets.c >>>> index cfed9c5..61b6e95 100644 >>>> --- a/qemu-sockets.c >>>> +++ b/qemu-sockets.c >>>> @@ -276,9 +276,6 @@ static int inet_connect_addr(struct addrinfo *addr, bool *in_progress, >>>> return -1; >>>> } >>>> qemu_setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)); >>>> - if (connect_state != NULL) { >>>> - socket_set_nonblock(sock); >>>> - } >>>> /* connect to peer */ >>>> do { >>>> rc = 0; >>>> @@ -732,7 +729,6 @@ int unix_connect_opts(QemuOpts *opts, Error **errp, >>>> connect_state = g_malloc0(sizeof(*connect_state)); >>>> connect_state->callback = callback; >>>> connect_state->opaque = opaque; >>>> - socket_set_nonblock(sock); >>>> } >>>> >>>> memset(&un, 0, sizeof(un)); >>> >>> Doesn't this break inet_nonblocking_connect() and >>> unix_nonblocking_connect()? >>> >>> In your cover letter, you wrote: >>> >>> Note: Writes has become blocking, and I have to change the "remove" >>> the feature now in qemu-sockets.c. Checked that migration was the >>> only user of that feature. If new users appear, they just need to add >>> the socket_set_nonblock() by hand. >>> >>> Yes, migration-{tcp,unix} are their only users, but if they want a >>> blocking socket now, why not use inet_connect() and unix_connect()? >>> >>> New users can't "just add socket_set_nonblock()". They'd have to add it >>> right where you deleted it: between qemu_socket() and connect(). Else >>> the connect() is blocking. >> >> Grrr. >> >> So, is there any way to make a connection that is non-blocking, but then >> writes are blocking? > > Which operations on the migration socket do you need to block, and which > ones do you need not to block? connect: not blocking (done on the iothread) writes: blocking, done in the migration thread. I think thet socket_set_block() that paolo says is the right solution. > > If connect() should block, use inet_connect() / unix_connect(). The > returned socket will be blocking. You can then switch to non-blocking > mode (and possibly back) at appropriate times. > > If connect() should not block, use inet_nonblocking_connect() and so > forth. Thanks, Juan.