Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751828AbdIVAAm (ORCPT ); Thu, 21 Sep 2017 20:00:42 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:29841 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751748AbdIVAAl (ORCPT ); Thu, 21 Sep 2017 20:00:41 -0400 Subject: Re: [PATCH v4 08/13] xen/pvcalls: implement accept command To: Stefano Stabellini , xen-devel@lists.xen.org Cc: linux-kernel@vger.kernel.org, jgross@suse.com, Stefano Stabellini References: <1505516440-11111-1-git-send-email-sstabellini@kernel.org> <1505516440-11111-8-git-send-email-sstabellini@kernel.org> From: Boris Ostrovsky Message-ID: <80eeb92b-4253-d1f0-fae8-fe288a831213@oracle.com> Date: Thu, 21 Sep 2017 20:00:22 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <1505516440-11111-8-git-send-email-sstabellini@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4062 Lines: 137 > +int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags) > +{ > + struct pvcalls_bedata *bedata; > + struct sock_mapping *map; > + struct sock_mapping *map2 = NULL; > + struct xen_pvcalls_request *req; > + int notify, req_id, ret, evtchn, nonblock; > + > + pvcalls_enter; > + if (!pvcalls_front_dev) { > + pvcalls_exit; > + return -ENOTCONN; > + } > + bedata = dev_get_drvdata(&pvcalls_front_dev->dev); > + > + map = (struct sock_mapping *) sock->sk->sk_send_head; > + if (!map) { > + pvcalls_exit; > + return -ENOTSOCK; > + } > + > + if (map->passive.status != PVCALLS_STATUS_LISTEN) { > + pvcalls_exit; > + return -EINVAL; > + } > + > + nonblock = flags & SOCK_NONBLOCK; > + /* > + * Backend only supports 1 inflight accept request, will return > + * errors for the others > + */ > + if (test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT, > + (void *)&map->passive.flags)) { > + req_id = READ_ONCE(map->passive.inflight_req_id); > + if (req_id != PVCALLS_INVALID_ID && > + READ_ONCE(bedata->rsp[req_id].req_id) == req_id) { > + map2 = map->passive.accept_map; > + goto received; > + } > + if (nonblock) { > + pvcalls_exit; > + return -EAGAIN; > + } > + if (wait_event_interruptible(map->passive.inflight_accept_req, > + !test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT, > + (void *)&map->passive.flags))) { > + pvcalls_exit; > + return -EINTR; > + } > + } > + > + spin_lock(&bedata->socket_lock); > + ret = get_request(bedata, &req_id); > + if (ret < 0) { > + spin_unlock(&bedata->socket_lock); > + pvcalls_exit; > + return ret; > + } > + map2 = kzalloc(sizeof(*map2), GFP_KERNEL); > + if (map2 == NULL) { > + spin_unlock(&bedata->socket_lock); > + pvcalls_exit; > + return -ENOMEM; > + } > + ret = create_active(map2, &evtchn); > + if (ret < 0) { > + kfree(map2); > + spin_unlock(&bedata->socket_lock); > + pvcalls_exit; > + return -ENOMEM; > + } Do you need to clear PVCALLS_FLAG_ACCEPT_INFLIGHT bit on errors (except for EAGAIN/EINTR)? > + list_add_tail(&map2->list, &bedata->socket_mappings); > + > + req = RING_GET_REQUEST(&bedata->ring, req_id); > + req->req_id = req_id; > + req->cmd = PVCALLS_ACCEPT; > + req->u.accept.id = (uint64_t) map; > + req->u.accept.ref = map2->active.ref; > + req->u.accept.id_new = (uint64_t) map2; > + req->u.accept.evtchn = evtchn; > + map->passive.accept_map = map2; > + > + bedata->ring.req_prod_pvt++; > + RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify); > + spin_unlock(&bedata->socket_lock); > + if (notify) > + notify_remote_via_irq(bedata->irq); > + /* We could check if we have received a response before returning. */ > + if (nonblock) { > + WRITE_ONCE(map->passive.inflight_req_id, req_id); > + pvcalls_exit; > + return -EAGAIN; > + } > + > + if (wait_event_interruptible(bedata->inflight_req, > + READ_ONCE(bedata->rsp[req_id].req_id) == req_id)) { > + pvcalls_exit; > + return -EINTR; > + } > + > +received: > + map2->sock = newsock; > + newsock->sk = kzalloc(sizeof(*newsock->sk), GFP_KERNEL); > + if (!newsock->sk) { > + WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID); > + WRITE_ONCE(map->passive.inflight_req_id, PVCALLS_INVALID_ID); > + pvcalls_front_free_map(bedata, map2); > + kfree(map2); > + pvcalls_exit; > + return -ENOMEM; > + } > + newsock->sk->sk_send_head = (void *)map2; > + > + clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT, (void *)&map->passive.flags); > + wake_up(&map->passive.inflight_accept_req); > + > + ret = bedata->rsp[req_id].ret; > + /* read ret, then set this rsp slot to be reused */ > + smp_mb(); > + WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID); > + WRITE_ONCE(map->passive.inflight_req_id, PVCALLS_INVALID_ID); Should inflight_req_id be cleared at the same time as PVCALLS_FLAG_ACCEPT_INFLIGHT? They kind of belong together, don't they? And I wonder whether you actually need the flag --- can you just key off map->passive.inflight_req_id not being PVCALLS_INVALID_ID? (and again, I am not sure about all READ/WRITE_ONCE() macros here). -boris