From patchwork Thu Jan 7 14:16:47 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 359709 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 51104C432C3 for ; Thu, 7 Jan 2021 14:19:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2B1262311E for ; Thu, 7 Jan 2021 14:19:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726229AbhAGOT3 (ORCPT ); Thu, 7 Jan 2021 09:19:29 -0500 Received: from mail.kernel.org ([198.145.29.99]:39050 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729098AbhAGOR2 (ORCPT ); Thu, 7 Jan 2021 09:17:28 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7FFBC23340; Thu, 7 Jan 2021 14:16:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1610029015; bh=AgyAM6uAwY/jDTnLkhu2YpKgeiOVtG0VcU/xbuvlV5M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rWVHwT4phuwe7xN4+hfHGg3AB5M4zdlSnfqlGODhZXntl3KulHXpCO6nvIOHhx8sw Dfdlw74ztVB00G1nM6hUoE0aEQtKkCCLNWIPD7UWwQlWthh6aR3Z914Q3Nkc8Mfc+f cuisMqUkREshTdbau8MKKsn8BTpfFwX3x3+heY9c= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, SeongJae Park , Michael Kurth , Pawel Wieczorkiewicz , Juergen Gross Subject: [PATCH 4.9 27/32] xen/xenbus: Count pending messages for each watch Date: Thu, 7 Jan 2021 15:16:47 +0100 Message-Id: <20210107140829.157470056@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210107140827.866214702@linuxfoundation.org> References: <20210107140827.866214702@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: SeongJae Park commit 3dc86ca6b4c8cfcba9da7996189d1b5a358a94fc upstream. This commit adds a counter of pending messages for each watch in the struct. It is used to skip unnecessary pending messages lookup in 'unregister_xenbus_watch()'. It could also be used in 'will_handle' callback. This is part of XSA-349 Cc: stable@vger.kernel.org Signed-off-by: SeongJae Park Reported-by: Michael Kurth Reported-by: Pawel Wieczorkiewicz Reviewed-by: Juergen Gross Signed-off-by: Juergen Gross Signed-off-by: Greg Kroah-Hartman --- drivers/xen/xenbus/xenbus_xs.c | 31 +++++++++++++++++++------------ include/xen/xenbus.h | 2 ++ 2 files changed, 21 insertions(+), 12 deletions(-) --- a/drivers/xen/xenbus/xenbus_xs.c +++ b/drivers/xen/xenbus/xenbus_xs.c @@ -699,6 +699,8 @@ int register_xenbus_watch(struct xenbus_ sprintf(token, "%lX", (long)watch); + watch->nr_pending = 0; + down_read(&xs_state.watch_mutex); spin_lock(&watches_lock); @@ -748,12 +750,15 @@ void unregister_xenbus_watch(struct xenb /* Cancel pending watch events. */ spin_lock(&watch_events_lock); - list_for_each_entry_safe(msg, tmp, &watch_events, list) { - if (msg->u.watch.handle != watch) - continue; - list_del(&msg->list); - kfree(msg->u.watch.vec); - kfree(msg); + if (watch->nr_pending) { + list_for_each_entry_safe(msg, tmp, &watch_events, list) { + if (msg->u.watch.handle != watch) + continue; + list_del(&msg->list); + kfree(msg->u.watch.vec); + kfree(msg); + } + watch->nr_pending = 0; } spin_unlock(&watch_events_lock); @@ -800,7 +805,6 @@ void xs_suspend_cancel(void) static int xenwatch_thread(void *unused) { - struct list_head *ent; struct xs_stored_msg *msg; for (;;) { @@ -813,13 +817,15 @@ static int xenwatch_thread(void *unused) mutex_lock(&xenwatch_mutex); spin_lock(&watch_events_lock); - ent = watch_events.next; - if (ent != &watch_events) - list_del(ent); + msg = list_first_entry_or_null(&watch_events, + struct xs_stored_msg, list); + if (msg) { + list_del(&msg->list); + msg->u.watch.handle->nr_pending--; + } spin_unlock(&watch_events_lock); - if (ent != &watch_events) { - msg = list_entry(ent, struct xs_stored_msg, list); + if (msg) { msg->u.watch.handle->callback( msg->u.watch.handle, (const char **)msg->u.watch.vec, @@ -909,6 +915,7 @@ static int process_msg(void) msg->u.watch.vec_size))) { spin_lock(&watch_events_lock); list_add_tail(&msg->list, &watch_events); + msg->u.watch.handle->nr_pending++; wake_up(&watch_events_waitq); spin_unlock(&watch_events_lock); } else { --- a/include/xen/xenbus.h +++ b/include/xen/xenbus.h @@ -58,6 +58,8 @@ struct xenbus_watch /* Path being watched. */ const char *node; + unsigned int nr_pending; + /* * Called just before enqueing new event while a spinlock is held. * The event will be discarded if this callback returns false.