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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 68BC2C433FF for ; Wed, 14 Aug 2019 17:25:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3C2AB20665 for ; Wed, 14 Aug 2019 17:25:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565803536; bh=b2zNZyKjcECupHNHtgikwqMvVgIIB0qbiiwmrBACDAM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=hLletH2TlAzYMy0xTxWmXz7+vU4H/vqgRsoC3XNSWsXXk1P6oZFp5u+TVuWfrAIBn mshMeY+z00diyr2ZMi4zXgRxMnuQu2yNuHnaWzs9AJmYJHwN+CkfoYZO62pgMcopzY pMCjhZFvrZXIdDbiiNHHTbuwPrs1DHOyaY5sgR5M= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728367AbfHNRZb (ORCPT ); Wed, 14 Aug 2019 13:25:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:54722 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729479AbfHNRFq (ORCPT ); Wed, 14 Aug 2019 13:05:46 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 075FE2084D; Wed, 14 Aug 2019 17:05:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565802345; bh=b2zNZyKjcECupHNHtgikwqMvVgIIB0qbiiwmrBACDAM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Zx/x3+iQPhZuniANkZKN+dMjavidf3MmfERdoJ0WNeMgRQC0ZqK0JiMjiOkcAeqpw FWyxOgughTWwN6HXX2NrHCc1KwRucyD8FaURiEgnf2e7HPZE3WgIf6phaFpJx3BNb0 BxK3GfFVSv920ATqrXcj84B26FHDrUo8/HJTrOd8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Oleg Nesterov , Josef Bacik , Jens Axboe , Sasha Levin Subject: [PATCH 5.2 062/144] rq-qos: use a mb for got_token Date: Wed, 14 Aug 2019 19:00:18 +0200 Message-Id: <20190814165802.430179590@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190814165759.466811854@linuxfoundation.org> References: <20190814165759.466811854@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org [ 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