From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49825) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Whz6Q-0005F1-7l for qemu-devel@nongnu.org; Wed, 07 May 2014 06:29:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Whz6J-00064v-V8 for qemu-devel@nongnu.org; Wed, 07 May 2014 06:29:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:15310) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Whz6J-00064l-MU for qemu-devel@nongnu.org; Wed, 07 May 2014 06:29:23 -0400 Message-ID: <536A0AF8.7030600@redhat.com> Date: Wed, 07 May 2014 12:29:12 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1398956086-20171-1-git-send-email-stefanha@redhat.com> <1398956086-20171-9-git-send-email-stefanha@redhat.com> <20140507100745.GD1771@stefanha-thinkpad.muc.redhat.com> In-Reply-To: <20140507100745.GD1771@stefanha-thinkpad.muc.redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 08/22] iscsi: implement .bdrv_detach/attach_aio_context() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi , Peter Lieven Cc: Kevin Wolf , Stefan Hajnoczi , "Shergill, Gurinder" , qemu-devel@nongnu.org, Ronnie Sahlberg , "Vinod, Chegu" Il 07/05/2014 12:07, Stefan Hajnoczi ha scritto: > On Fri, May 02, 2014 at 12:39:06AM +0200, Peter Lieven wrote: >>> +static void iscsi_attach_aio_context(BlockDriverState *bs, >>> + AioContext *new_context) >>> +{ >>> + IscsiLun *iscsilun = bs->opaque; >>> + >>> + iscsilun->aio_context = new_context; >>> + iscsi_set_events(iscsilun); >>> + >>> +#if defined(LIBISCSI_FEATURE_NOP_COUNTER) >>> + /* Set up a timer for sending out iSCSI NOPs */ >>> + iscsilun->nop_timer = aio_timer_new(iscsilun->aio_context, >>> + QEMU_CLOCK_REALTIME, SCALE_MS, >>> + iscsi_nop_timed_event, iscsilun); >>> + timer_mod(iscsilun->nop_timer, >>> + qemu_clock_get_ms(QEMU_CLOCK_REALTIME) + NOP_INTERVAL); >>> +#endif >>> +} >> >> Is it still guaranteed that iscsi_nop_timed_event for a target is not invoked >> while we are in another function/callback of the iscsi driver for the same target? Yes, since the timer is in the same AioContext as the iscsi driver callbacks. > This is a good point. > > Previously, the nop timer was deferred until the qemu_aio_wait() loop > terminates. > > With this patch the nop timer fires during aio_poll() loops for any > synchronous emulation that QEMU does (including iscsi_aio_cancel() and > .bdrv_ioctl() in block/iscsi.c). > > I don't know libiscsi well enough to understand the implications. I can > see that iscsi_reconnect() resends in-flight commands. So what's the > upshot of all this? I think it's fine. The target will process NOPs asynchronously, so iscsi_nop_timed_event will see no NOP in flight if the target is working properly. > BTW, is iscsi_reconnect() the right libiscsi interface to use since it > is synchronous? It seems like this would block QEMU until the socket > has connected! The guest would be frozen. There is no asynchronous interface yet for reconnection, unfortunately. Paolo