From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35845) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bMQha-0008Um-3Z for qemu-devel@nongnu.org; Sun, 10 Jul 2016 22:12:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bMQhU-0001JZ-MX for qemu-devel@nongnu.org; Sun, 10 Jul 2016 22:12:04 -0400 Received: from [59.151.112.132] (port=53509 helo=heian.cn.fujitsu.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bMQhT-0001IP-FD for qemu-devel@nongnu.org; Sun, 10 Jul 2016 22:12:00 -0400 References: <1466592545-9105-1-git-send-email-zhangchen.fnst@cn.fujitsu.com> <20160708014823.GA13961@ad.usersys.redhat.com> <20160708085401.GA3205@redhat.com> <23246597-319a-d568-6fcc-738f5eb1341a@redhat.com> From: Zhang Chen Message-ID: <57830099.5030108@cn.fujitsu.com> Date: Mon, 11 Jul 2016 10:12:41 +0800 MIME-Version: 1.0 In-Reply-To: <23246597-319a-d568-6fcc-738f5eb1341a@redhat.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC PATCH V2] qemu-char: Fix context for g_source_attach() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini , "Daniel P. Berrange" , Fam Zheng Cc: qemu devel , "eddie . dong" , Jason Wang , Li Zhijian On 07/08/2016 10:27 PM, Paolo Bonzini wrote: > > On 08/07/2016 10:54, Daniel P. Berrange wrote: >> On Fri, Jul 08, 2016 at 09:48:23AM +0800, Fam Zheng wrote: >>> On Wed, 06/22 18:49, Zhang Chen wrote: >>>> We want to poll and handle chardev in another thread >>>> other than main loop. But qemu_chr_add_handlers() can only >>>> work for global default context other than thread default context. >>>> So we use g_source_attach(xx, g_main_context_get_thread_default()) >>>> replace g_source_attach(xx, NULL) to attach g_source. >>>> Comments from jason. >>>> >>>> Signed-off-by: Zhang Chen >>>> Signed-off-by: Jason Wang >>>> --- >>>> io/channel.c | 2 +- >>>> qemu-char.c | 6 +++--- >>>> 2 files changed, 4 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/io/channel.c b/io/channel.c >>>> index 692eb17..cd25677 100644 >>>> --- a/io/channel.c >>>> +++ b/io/channel.c >>>> @@ -146,7 +146,7 @@ guint qio_channel_add_watch(QIOChannel *ioc, >>>> >>>> g_source_set_callback(source, (GSourceFunc)func, user_data, notify); >>>> >>>> - id = g_source_attach(source, NULL); >>>> + id = g_source_attach(source, g_main_context_get_thread_default()); >>>> g_source_unref(source); >>>> >>>> return id; >>>> diff --git a/qemu-char.c b/qemu-char.c >>>> index 84f49ac..4340457 100644 >>>> --- a/qemu-char.c >>>> +++ b/qemu-char.c >>>> @@ -859,7 +859,7 @@ static gboolean io_watch_poll_prepare(GSource *source, gint *timeout_) >>>> iwp->src = qio_channel_create_watch( >>>> iwp->ioc, G_IO_IN | G_IO_ERR | G_IO_HUP | G_IO_NVAL); >>>> g_source_set_callback(iwp->src, iwp->fd_read, iwp->opaque, NULL); >>>> - g_source_attach(iwp->src, NULL); >>>> + g_source_attach(iwp->src, g_main_context_get_thread_default()); >>>> } else { >>>> g_source_destroy(iwp->src); >>>> g_source_unref(iwp->src); >>>> @@ -918,7 +918,7 @@ static guint io_add_watch_poll(QIOChannel *ioc, >>>> iwp->fd_read = (GSourceFunc) fd_read; >>>> iwp->src = NULL; >>>> >>>> - tag = g_source_attach(&iwp->parent, NULL); >>>> + tag = g_source_attach(&iwp->parent, g_main_context_get_thread_default()); >>>> g_source_unref(&iwp->parent); >>>> return tag; >>>> } >>>> @@ -3982,7 +3982,7 @@ int qemu_chr_fe_add_watch(CharDriverState *s, GIOCondition cond, >>>> } >>>> >>>> g_source_set_callback(src, (GSourceFunc)func, user_data, NULL); >>>> - tag = g_source_attach(src, NULL); >>>> + tag = g_source_attach(src, g_main_context_get_thread_default()); >>>> g_source_unref(src); >>>> >>>> return tag; >>>> -- >>> IIRC this opens a gate for your special thread (COLO compare thread?) to use >>> QIOChannel. >> I've no real objection to this proposed patch, though it is fairly pointless >> to take it now without seeing any following patch that actually makes use >> of this added feature. > I agree. Should I move this patch to the "[RFC PATCH V5 0/4] Introduce COLO-compare" patch set? that can show how it works. you can see this patch for how to use: http://lists.nongnu.org/archive/html/qemu-devel/2016-06/msg06754.html > >>> I think in the long run it is better to think about allowing integrating QIO to >>> AioContext, to support its usage outside main loop. Given how opaque GSource >>> is, I'm not sure how feasible that is, or how useful it will be. Anyway we >>> should definitely hear more opinions from Daniel and Paolo. >> Personally I think it is preferable to stick as close to the standard GSource >> model as possible, as that's widely used & well understood API, compared to the >> QEMU specific AioContext. > AioContext is more optimized for the case where the callbacks are > static. In general this is not the case for qemu-char.c. I don't sure AioContext can do this job good, but I think we can make qemu more flexible to do same one job. All roads lead to Rome. Thanks Zhang Chen > Paolo > > > . > -- Thanks zhangchen