From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58709) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1agNad-0003Qr-RY for qemu-devel@nongnu.org; Wed, 16 Mar 2016 22:23:08 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1agNaZ-0001MY-L8 for qemu-devel@nongnu.org; Wed, 16 Mar 2016 22:23:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37731) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1agNaZ-0001MU-GM for qemu-devel@nongnu.org; Wed, 16 Mar 2016 22:23:03 -0400 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) by mx1.redhat.com (Postfix) with ESMTPS id 36096C00EB06 for ; Thu, 17 Mar 2016 02:23:03 +0000 (UTC) Date: Thu, 17 Mar 2016 10:23:01 +0800 From: Fam Zheng Message-ID: <20160317022301.GG23821@ad.usersys.redhat.com> References: <1458137817-15383-1-git-send-email-pbonzini@redhat.com> <1458137817-15383-6-git-send-email-pbonzini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1458137817-15383-6-git-send-email-pbonzini@redhat.com> Subject: Re: [Qemu-devel] [PATCH v2 05/16] mirror: use bottom half to re-enter coroutine List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: qemu-devel@nongnu.org, stefanha@redhat.com On Wed, 03/16 15:16, Paolo Bonzini wrote: > Signed-off-by: Paolo Bonzini > --- > v1->v2: use aio_bh_new() [Fam] > > block/mirror.c | 24 ++++++++++++++++++++---- > 1 file changed, 20 insertions(+), 4 deletions(-) > > diff --git a/block/mirror.c b/block/mirror.c > index 9635fa8..2c7874d 100644 > --- a/block/mirror.c > +++ b/block/mirror.c > @@ -72,6 +72,7 @@ typedef struct MirrorOp { > QEMUIOVector qiov; > int64_t sector_num; > int nb_sectors; > + QEMUBH *co_enter_bh; > } MirrorOp; > > static BlockErrorAction mirror_error_action(MirrorBlockJob *s, bool read, > @@ -87,6 +88,18 @@ static BlockErrorAction mirror_error_action(MirrorBlockJob *s, bool read, > } > } > > +static void mirror_bh_cb(void *opaque) > +{ > + MirrorOp *op = opaque; > + MirrorBlockJob *s = op->s; > + > + qemu_bh_delete(op->co_enter_bh); > + g_free(op); > + if (s->waiting_for_io) { > + qemu_coroutine_enter(s->common.co, NULL); > + } > +} > + > static void mirror_iteration_done(MirrorOp *op, int ret) > { > MirrorBlockJob *s = op->s; > @@ -117,11 +130,14 @@ static void mirror_iteration_done(MirrorOp *op, int ret) > } > > qemu_iovec_destroy(&op->qiov); > - g_free(op); > > - if (s->waiting_for_io) { > - qemu_coroutine_enter(s->common.co, NULL); > - } > + /* The I/O operation is not finished until the callback returns. > + * If we call qemu_coroutine_enter here, there is the possibility > + * of a deadlock when the coroutine calls bdrv_drained_begin. > + */ > + op->co_enter_bh = aio_bh_new(bdrv_get_aio_context(s->target), > + mirror_bh_cb, op); > + qemu_bh_schedule(op->co_enter_bh); I think we can conditionally create the BH only if s->waiting_for_io is true, but the else branch is less important, so: Reviewed-by: Fam Zheng