Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754135AbdFNArT (ORCPT ); Tue, 13 Jun 2017 20:47:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:32888 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753947AbdFNArR (ORCPT ); Tue, 13 Jun 2017 20:47:17 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0C966239A8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=sstabellini@kernel.org Date: Tue, 13 Jun 2017 17:47:11 -0700 (PDT) From: Stefano Stabellini X-X-Sender: sstabellini@sstabellini-ThinkPad-X260 To: Juergen Gross cc: Stefano Stabellini , xen-devel@lists.xen.org, linux-kernel@vger.kernel.org, boris.ostrovsky@oracle.com, Stefano Stabellini Subject: Re: [PATCH v3 11/18] xen/pvcalls: implement accept command In-Reply-To: Message-ID: References: <1496431915-20774-1-git-send-email-sstabellini@kernel.org> <1496431915-20774-11-git-send-email-sstabellini@kernel.org> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5929 Lines: 193 On Tue, 13 Jun 2017, Juergen Gross wrote: > On 02/06/17 21:31, Stefano Stabellini wrote: > > Implement the accept command by calling inet_accept. To avoid blocking > > in the kernel, call inet_accept(O_NONBLOCK) from a workqueue, which get > > scheduled on sk_data_ready (for a passive socket, it means that there > > are connections to accept). > > > > Use the reqcopy field to store the request. Accept the new socket from > > the delayed work function, create a new sock_mapping for it, map > > the indexes page and data ring, and reply to the other end. Allocate an > > ioworker for the socket. > > > > Only support one outstanding blocking accept request for every socket at > > any time. > > > > Add a field to sock_mapping to remember the passive socket from which an > > active socket was created. > > > > Signed-off-by: Stefano Stabellini > > CC: boris.ostrovsky@oracle.com > > CC: jgross@suse.com > > --- > > drivers/xen/pvcalls-back.c | 109 ++++++++++++++++++++++++++++++++++++++++++++- > > 1 file changed, 108 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c > > index a75586e..f1173f4 100644 > > --- a/drivers/xen/pvcalls-back.c > > +++ b/drivers/xen/pvcalls-back.c > > @@ -65,6 +65,7 @@ struct pvcalls_ioworker { > > struct sock_mapping { > > struct list_head list; > > struct pvcalls_fedata *priv; > > + struct sockpass_mapping *sockpass; > > struct socket *sock; > > uint64_t id; > > grant_ref_t ref; > > @@ -275,10 +276,79 @@ static int pvcalls_back_release(struct xenbus_device *dev, > > > > static void __pvcalls_back_accept(struct work_struct *work) > > { > > + struct sockpass_mapping *mappass = container_of( > > + work, struct sockpass_mapping, register_work); > > + struct sock_mapping *map; > > + struct pvcalls_ioworker *iow; > > + struct pvcalls_fedata *priv; > > + struct socket *sock; > > + struct xen_pvcalls_response *rsp; > > + struct xen_pvcalls_request *req; > > + int notify; > > + int ret = -EINVAL; > > + unsigned long flags; > > + > > + priv = mappass->priv; > > + /* We only need to check the value of "cmd" atomically on read. */ > > + spin_lock_irqsave(&mappass->copy_lock, flags); > > + req = &mappass->reqcopy; > > + if (req->cmd != PVCALLS_ACCEPT) { > > + spin_unlock_irqrestore(&mappass->copy_lock, flags); > > + return; > > + } > > + spin_unlock_irqrestore(&mappass->copy_lock, flags); > > What about: > req = &mappass->reqcopy; > if (ACCESS_ONCE(req->cmd) != PVCALLS_ACCEPT) > return; > > I can't see the need for taking a lock here. Sure, good idea > > + > > + sock = sock_alloc(); > > + if (sock == NULL) > > + goto out_error; > > + sock->type = mappass->sock->type; > > + sock->ops = mappass->sock->ops; > > + > > + ret = inet_accept(mappass->sock, sock, O_NONBLOCK, true); > > + if (ret == -EAGAIN) { > > + sock_release(sock); > > + goto out_error; > > + } > > + > > + map = pvcalls_new_active_socket(priv, > > + req->u.accept.id_new, > > + req->u.accept.ref, > > + req->u.accept.evtchn, > > + sock); > > + if (!map) { > > + sock_release(sock); > > + goto out_error; > > + } > > + > > + map->sockpass = mappass; > > + iow = &map->ioworker; > > + atomic_inc(&map->read); > > + atomic_inc(&map->io); > > + queue_work_on(iow->cpu, iow->wq, &iow->register_work); > > + > > +out_error: > > + rsp = RING_GET_RESPONSE(&priv->ring, priv->ring.rsp_prod_pvt++); > > + rsp->req_id = req->req_id; > > + rsp->cmd = req->cmd; > > + rsp->u.accept.id = req->u.accept.id; > > + rsp->ret = ret; > > + RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&priv->ring, notify); > > + if (notify) > > + notify_remote_via_irq(priv->irq); > > + > > + spin_lock_irqsave(&mappass->copy_lock, flags); > > + mappass->reqcopy.cmd = 0; > > + spin_unlock_irqrestore(&mappass->copy_lock, flags); > > ACCESS_ONCE(mappass->reqcopy.cmd) = 0; OK > > } > > > > static void pvcalls_pass_sk_data_ready(struct sock *sock) > > { > > + struct sockpass_mapping *mappass = sock->sk_user_data; > > + > > + if (mappass == NULL) > > + return; > > + > > + queue_work(mappass->wq, &mappass->register_work); > > } > > > > static int pvcalls_back_bind(struct xenbus_device *dev, > > @@ -380,7 +450,44 @@ static int pvcalls_back_listen(struct xenbus_device *dev, > > static int pvcalls_back_accept(struct xenbus_device *dev, > > struct xen_pvcalls_request *req) > > { > > - return 0; > > + struct pvcalls_fedata *priv; > > + struct sockpass_mapping *mappass; > > + int ret = -EINVAL; > > + struct xen_pvcalls_response *rsp; > > + unsigned long flags; > > + > > + priv = dev_get_drvdata(&dev->dev); > > + > > + mappass = radix_tree_lookup(&priv->socketpass_mappings, > > + req->u.accept.id); > > + if (mappass == NULL) > > + goto out_error; > > + > > + /* > > + * Limitation of the current implementation: only support one > > + * concurrent accept or poll call on one socket. > > + */ > > + spin_lock_irqsave(&mappass->copy_lock, flags); > > + if (mappass->reqcopy.cmd != 0) { > > + spin_unlock_irqrestore(&mappass->copy_lock, flags); > > + ret = -EINTR; > > + goto out_error; > > + } > > + > > + mappass->reqcopy = *req; > > This time you need the lock, however you should use: > > ACCESS_ONCE(mappass->reqcopy) = *req; I don't think that guarantees atomic accesses to the cmd field of the struct. Shouldn't this be: ACCESS_ONCE(mappass->reqcopy.cmd) = req->cmd; mappass->reqcopy = *req; > > + spin_unlock_irqrestore(&mappass->copy_lock, flags); > > + queue_work(mappass->wq, &mappass->register_work); > > + > > + /* Tell the caller we don't need to send back a notification yet */ > > + return -1; > > + > > +out_error: > > + rsp = RING_GET_RESPONSE(&priv->ring, priv->ring.rsp_prod_pvt++); > > + rsp->req_id = req->req_id; > > + rsp->cmd = req->cmd; > > + rsp->u.accept.id = req->u.accept.id; > > + rsp->ret = ret; > > + return ret; > > return 0? Yes, thanks