From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50579) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZKP3H-000629-Qn for qemu-devel@nongnu.org; Wed, 29 Jul 2015 06:57:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZKP3G-0000Jw-Vz for qemu-devel@nongnu.org; Wed, 29 Jul 2015 06:57:35 -0400 Date: Wed, 29 Jul 2015 18:57:25 +0800 From: Fam Zheng Message-ID: <20150729105725.GA10376@ad.nay.redhat.com> References: <1438144934-23619-1-git-send-email-famz@redhat.com> <1438144934-23619-12-git-send-email-famz@redhat.com> <55B882C1.8070500@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55B882C1.8070500@redhat.com> Subject: Re: [Qemu-devel] [PATCH v2 11/11] block: Only poll block layer fds in bdrv_aio_poll List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: kwolf@redhat.com, stefanha@redhat.com, qemu-devel@nongnu.org, qemu-block@nongnu.org On Wed, 07/29 09:37, Paolo Bonzini wrote: > > > On 29/07/2015 06:42, Fam Zheng wrote: > > @@ -2613,6 +2613,8 @@ bool bdrv_aio_poll(AioContext *ctx, bool blocking) > > { > > bool ret; > > > > + aio_disable_clients(ctx, AIO_CLIENT_DATAPLANE | AIO_CLIENT_NBD_SERVER); > > ret = aio_poll(ctx, blocking); > > + aio_enable_clients(ctx, AIO_CLIENT_DATAPLANE | AIO_CLIENT_NBD_SERVER); > > return ret; > > This is not enough, because another thread's aio_poll can sneak in > between calls to bdrv_aio_poll if the AioContext lock is released, and > they will use the full set of clients. > > Similar to your v1, it works with the large critical sections we > currently have, but it has the same problem in the longer term. Can we add more disable/enable pairs around bdrv_drain on top? Fam > > The clients have to be disabled around calls to bdrv_drain, as you were > doing when you had pause/resume notifiers. Patches 1-8 however are ok. > > Paolo >