From mboxrd@z Thu Jan 1 00:00:00 1970 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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 89B5CC32750 for ; Fri, 2 Aug 2019 13:20:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 587F921849 for ; Fri, 2 Aug 2019 13:20:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564752011; bh=ritnmQKeXCNUkl00pdK+bMvgCPeyD/nYb7rU9HK3wAE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=rEg8cnaU7QzeUGRq2rN114vVSrugGroPaMWacHYRgY5/NCwixuqFIFRuDcFa8Vhk6 3gLq5/iWroJhpXpTs4MHth1cgGJJCc/eR40BKiQXbQpDICXCWMVyG+QQBrWlUVnkK/ fByTadrVGxhI9Q6NKgPKk60Xeu+RWlBy7GK6sVKM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393295AbfHBNUK (ORCPT ); Fri, 2 Aug 2019 09:20:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:58484 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2393281AbfHBNUJ (ORCPT ); Fri, 2 Aug 2019 09:20:09 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A2D19218A3; Fri, 2 Aug 2019 13:20:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564752008; bh=ritnmQKeXCNUkl00pdK+bMvgCPeyD/nYb7rU9HK3wAE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=KvXV1hSIK+Ae3Gj1VvZ8kwBVeWWfKa+aEfIUNKxDJN5vYfnkuIn+Q7Tegab0RUPxO LssHxI/JAZf7sDnhL7ldvHNBZBVVEpOgepEHn3BN1S8HNxPFP0fDhQlY9FEWiCY/2j rGgVlurPZTj0S2uDxEp6d6x3dxZVoHILsXLHjow4= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Josef Bacik , Oleg Nesterov , Jens Axboe , Sasha Levin , linux-block@vger.kernel.org Subject: [PATCH AUTOSEL 5.2 14/76] rq-qos: use a mb for got_token Date: Fri, 2 Aug 2019 09:18:48 -0400 Message-Id: <20190802131951.11600-14-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190802131951.11600-1-sashal@kernel.org> References: <20190802131951.11600-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Josef Bacik [ Upstream commit ac38297f7038cd5b80d66f8809c7bbf5b70031f3 ] Oleg noticed that our checking of data.got_token is unsafe in the cleanup case, and should really use a memory barrier. Use a wmb on the write side, and a rmb() on the read side. We don't need one in the main loop since we're saved by set_current_state(). Reviewed-by: Oleg Nesterov Signed-off-by: Josef Bacik Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/blk-rq-qos.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/block/blk-rq-qos.c b/block/blk-rq-qos.c index e3ab75e4df9ea..06d024204f504 100644 --- a/block/blk-rq-qos.c +++ b/block/blk-rq-qos.c @@ -202,6 +202,7 @@ static int rq_qos_wake_function(struct wait_queue_entry *curr, return -1; data->got_token = true; + smp_wmb(); list_del_init(&curr->entry); wake_up_process(data->task); return 1; @@ -245,6 +246,7 @@ void rq_qos_wait(struct rq_wait *rqw, void *private_data, prepare_to_wait_exclusive(&rqw->wait, &data.wq, TASK_UNINTERRUPTIBLE); do { + /* The memory barrier in set_task_state saves us here. */ if (data.got_token) break; if (!has_sleeper && acquire_inflight_cb(rqw, private_data)) { @@ -255,6 +257,7 @@ void rq_qos_wait(struct rq_wait *rqw, void *private_data, * which means we now have two. Put our local token * and wake anyone else potentially waiting for one. */ + smp_rmb(); if (data.got_token) cleanup_cb(rqw, private_data); break; -- 2.20.1