From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48240) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1X4XoU-00039S-Hk for qemu-devel@nongnu.org; Tue, 08 Jul 2014 12:00:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1X4XoO-0007vM-Bj for qemu-devel@nongnu.org; Tue, 08 Jul 2014 12:00:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52453) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1X4XoO-0007uf-4D for qemu-devel@nongnu.org; Tue, 08 Jul 2014 12:00:08 -0400 Date: Tue, 8 Jul 2014 17:59:56 +0200 From: Stefan Hajnoczi Message-ID: <20140708155956.GB11505@stefanha-thinkpad.redhat.com> References: <53BA8B49.9050709@de.ibm.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="zx4FCpZtqtKETZ7O" Content-Disposition: inline In-Reply-To: <53BA8B49.9050709@de.ibm.com> Subject: Re: [Qemu-devel] another locking issue in current dataplane code? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Christian Borntraeger Cc: Cornelia Huck , Kevin Wolf , ming.lei@canonical.com, "qemu-devel@nongnu.org" , Dominik Dingel --zx4FCpZtqtKETZ7O Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jul 07, 2014 at 01:58:01PM +0200, Christian Borntraeger wrote: > Now. If aio_poll never returns, we have a deadlock here.=20 > To me it looks like, that aio_poll could be called from iothread_run, eve= n if there are no outstanding request. > Opinions? Christian pointed out that iothread_run() can miss aio_notify() if a file descriptor becomes readable/writeable at the same time as the AioContext->notifier. aio_poll() will return true since progress was made and we are left with a hung QEMU. I sent Christian an initial patch to fix this but now both threads are stuck in rfifolock_lock() inside cond wait. That's very strange and should never happen. Still trying to figure out what is going on... Stefan --zx4FCpZtqtKETZ7O Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJTvBV8AAoJEJykq7OBq3PIaq4H/2jG5PIzS4U8GcH50EIHUTxz e7k3VwNOmN2el0ybhZuDWLDTUk9YGWWov9cn/Ig7W62/0VSdtAVyB+vJQQD6PY1z x1fC+TaVFy2V7ufUhEYIe/t7dP9mDkUTkf0n7owQ1vBQc6PMsXieG0HcuOzsMgU9 X7QdJQ28WPq9RIdg9Dr0vV+zlQl2XaKnrsBeVF6ZaOiqwEv+4IndN65C+3XFeRPj +9jkzaUGLExJC2WNBHOa9XWlDoRttN1W470Ld+tHuVHHbEsszQTCNC/XM357j0Zz GCMXRrm+xA9ACt3xuY+z/zt3/dXmrJdgrk/ay1gBbmDqek5oBZee8KqwhDrQxQ4= =YDZ5 -----END PGP SIGNATURE----- --zx4FCpZtqtKETZ7O--