Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753272AbdFMHZE (ORCPT ); Tue, 13 Jun 2017 03:25:04 -0400 Received: from mx2.suse.de ([195.135.220.15]:40843 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753143AbdFMHYp (ORCPT ); Tue, 13 Jun 2017 03:24:45 -0400 Subject: Re: [PATCH v3 11/18] xen/pvcalls: implement accept command To: Stefano Stabellini , xen-devel@lists.xen.org Cc: linux-kernel@vger.kernel.org, boris.ostrovsky@oracle.com, Stefano Stabellini References: <1496431915-20774-1-git-send-email-sstabellini@kernel.org> <1496431915-20774-11-git-send-email-sstabellini@kernel.org> From: Juergen Gross Message-ID: Date: Tue, 13 Jun 2017 09:24:41 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: <1496431915-20774-11-git-send-email-sstabellini@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: de-DE Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5410 Lines: 185 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. > + > + 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; > } > > 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; > + 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? Juergen > } > > static int pvcalls_back_poll(struct xenbus_device *dev, >