From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59907) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d6Fvw-00021e-T2 for qemu-devel@nongnu.org; Thu, 04 May 2017 08:32:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d6Fvt-0005Ba-Qy for qemu-devel@nongnu.org; Thu, 04 May 2017 08:32:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38930) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1d6Fvt-0005BC-KG for qemu-devel@nongnu.org; Thu, 04 May 2017 08:32:33 -0400 References: <20170504084135.7488.24715.stgit@PASHA-ISP> <20170504084210.7488.37561.stgit@PASHA-ISP> <000401d2c4c7$6d5b6d50$481247f0$@ru> <000801d2c4cd$3d3af720$b7b0e560$@ru> <58398574-88b5-3382-65e2-7208beccc09a@redhat.com> <000f01d2c4cf$7479f630$5d6de290$@ru> From: Paolo Bonzini Message-ID: Date: Thu, 4 May 2017 14:32:27 +0200 MIME-Version: 1.0 In-Reply-To: <000f01d2c4cf$7479f630$5d6de290$@ru> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v9 06/10] replay: fix save/load vm for non-empty queue List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Pavel Dovgalyuk , 'Pavel Dovgalyuk' , qemu-devel@nongnu.org Cc: kwolf@redhat.com, peter.maydell@linaro.org, mst@redhat.com, jasowang@redhat.com, quintela@redhat.com, kraxel@redhat.com On 04/05/2017 14:10, Pavel Dovgalyuk wrote: >> From: Paolo Bonzini [mailto:pbonzini@redhat.com] >> On 04/05/2017 13:54, Pavel Dovgalyuk wrote: >>>> From: Paolo Bonzini [mailto:pbonzini@redhat.com] >>>> On 04/05/2017 13:13, Pavel Dovgalyuk wrote: >>>>>>> This patch does not allows saving/loading vmstate when >>>>>>> replay events queue is not empty. There is no reliable >>>>>>> way to save events queue, because it describes internal >>>>>>> coroutine state. Therefore saving and loading operations >>>>>>> should be deferred to another record/replay step. >>>>>> >>>>>> Can it actually be non-empty after bdrv_drain_all? >>>>> >>>>> drain/flush cannot succeed, because started requests are >>>>> prisoned in the replay events queue. >>>> >>>> But that would apply to loading only. Saving should still be always >>>> possible. >>> >>> We can save it. But it wouldn't load correctly - replay queue will be empty after loading. >> >> When saving you can drain, and then the events queue should be empty. >> Or I am misunderstanding how it works, which is possible too. > > Drain will wait until the queue becomes empty. > Queue is processed only at checkpoints. > Checkpoints are met in iothread (at timers processing and so on). > But iothread is waiting for finishing the drain. What checkpoint can hang the drain during a save? Paolo