Re: [Qemu-devel] [PATCH 3/3] replay: introduce block devices record/replay

From: "Pavel Dovgalyuk" <dovgaluk@ispras.ru>
To: 'Kevin Wolf' <kwolf@redhat.com>
Cc: edgar.iglesias@xilinx.com, peter.maydell@linaro.org,
	igor.rubinov@gmail.com, mark.burton@greensocs.com,
	real@ispras.ru, hines@cert.org, qemu-devel@nongnu.org,
	maria.klimushenkova@ispras.ru, stefanha@redhat.com,
	pbonzini@redhat.com, batuzovk@ispras.ru, alex.bennee@linaro.org,
	fred.konrad@greensocs.com
Subject: Re: [Qemu-devel] [PATCH 3/3] replay: introduce block devices record/replay
Date: Mon, 15 Feb 2016 17:50:10 +0300	[thread overview]
Message-ID: <005601d16800$2b4fe500$81efaf00$@ru> (raw)
In-Reply-To: <20160215140635.GF5244@noname.str.redhat.com>

> From: Kevin Wolf [mailto:kwolf@redhat.com]
> > void replay_run_block_event(uint32_t id)
> > {
> >     Request *req;
> >     if (replay_mode == REPLAY_MODE_PLAY) {
> >         while (!(req = block_request_find(id))) {
> >             //aio_poll(bdrv_get_aio_context(req->bs), true);
> >             usleep(1);
> >         }
> 
> >         qemu_coroutine_enter(req->co, NULL);
> >     }
> > }
> >
> > > Can you provide more detail about the exact place where it's hanging,
> > > both in the coroutine and in the main "coroutine" that executes
> > > aio_poll()?

I've tried to replace usleep with aio_poll.
In this case replay cannot be made, because of recursive mutex lock:
aio_poll -> qemu_clock_get_ns -> <lock replay mutex> -> 
  replay_run_block_event -> aio_poll -> qemu_clock_get_ns -> <lock replay mutex> ->
  <assert failed>

Pavel Dovgalyuk