From patchwork Tue Jun 11 14:54:54 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roman Penyaev X-Patchwork-Id: 10987357 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0FEC314BB for ; Tue, 11 Jun 2019 14:55:54 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 00820288A0 for ; Tue, 11 Jun 2019 14:55:54 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id E900728688; Tue, 11 Jun 2019 14:55:53 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 824B8288AC for ; Tue, 11 Jun 2019 14:55:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404168AbfFKOzV (ORCPT ); Tue, 11 Jun 2019 10:55:21 -0400 Received: from mx2.suse.de ([195.135.220.15]:52630 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2404076AbfFKOzU (ORCPT ); Tue, 11 Jun 2019 10:55:20 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 7226AAF1F; Tue, 11 Jun 2019 14:55:19 +0000 (UTC) From: Roman Penyaev Cc: Roman Penyaev , Andrew Morton , Al Viro , Linus Torvalds , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 10/14] epoll: support polling from userspace for ep_modify() Date: Tue, 11 Jun 2019 16:54:54 +0200 Message-Id: <20190611145458.9540-11-rpenyaev@suse.de> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190611145458.9540-1-rpenyaev@suse.de> References: <20190611145458.9540-1-rpenyaev@suse.de> MIME-Version: 1.0 To: unlisted-recipients:; (no To-header on input) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When epfd is polled from userspace and item is being modified: 1. Update user item with new pointer or poll flags. 2. Add event to user ring if needed. Signed-off-by: Roman Penyaev Cc: Andrew Morton Cc: Al Viro Cc: Linus Torvalds Cc: linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org --- fs/eventpoll.c | 32 +++++++++++++++++++++++++++----- 1 file changed, 27 insertions(+), 5 deletions(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index edf7ba28bce0..9f0d48eb360e 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -2239,6 +2239,7 @@ static int ep_insert(struct eventpoll *ep, const struct epoll_event *event, static int ep_modify(struct eventpoll *ep, struct epitem *epi, const struct epoll_event *event) { + __poll_t revents; int pwake = 0; poll_table pt; @@ -2250,10 +2251,24 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, * Set the new event interest mask before calling f_op->poll(); * otherwise we might miss an event that happens between the * f_op->poll() call and the new event set registering. + * + * Use xchg() here because we can race with ep_clear_public_event_bits() + * for the case when events are polled from userspace. Internally + * ep_clear_public_event_bits() uses cmpxchg(), thus on some archs + * we can't mix normal writes and cmpxchg(). */ - epi->event.events = event->events; /* need barrier below */ + xchg(&epi->event.events, event->events); epi->event.data = event->data; /* protected by mtx */ - if (epi->event.events & EPOLLWAKEUP) { + + /* Update user item, barrier is below */ + if (ep_polled_by_user(ep)) { + struct uepitem *uepi = uep_item_from_epi(epi); + struct epoll_uitem *uitem; + + uitem = &ep->user_header->items[uepi->bit]; + WRITE_ONCE(uitem->events, event->events); + WRITE_ONCE(uitem->data, event->data); + } else if (epi->event.events & EPOLLWAKEUP) { if (!ep_has_wakeup_source(epi)) ep_create_wakeup_source(epi); } else if (ep_has_wakeup_source(epi)) { @@ -2286,12 +2301,19 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, * If the item is "hot" and it is not registered inside the ready * list, push it inside. */ - if (ep_item_poll(epi, &pt, 1)) { + revents = ep_item_poll(epi, &pt, 1); + if (revents) { + bool added = false; + write_lock_irq(&ep->lock); - if (!ep_is_linked(epi)) { + if (ep_polled_by_user(ep)) + added = ep_add_event_to_uring(epi, revents); + else if (!ep_is_linked(epi)) { list_add_tail(&epi->rdllink, &ep->rdllist); ep_pm_stay_awake(epi); - + added = true; + } + if (added) { /* Notify waiting tasks that events are available */ if (waitqueue_active(&ep->wq)) wake_up(&ep->wq);