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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CE17FC433F5 for ; Mon, 20 Dec 2021 15:20:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236388AbhLTPUU (ORCPT ); Mon, 20 Dec 2021 10:20:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40854 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239365AbhLTPSe (ORCPT ); Mon, 20 Dec 2021 10:18:34 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0CE57C00FC7C; Mon, 20 Dec 2021 06:59:25 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id C9067B80EF1; Mon, 20 Dec 2021 14:59:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0307AC36AE8; Mon, 20 Dec 2021 14:59:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1640012362; bh=7JvV31XUvineH8ApZInp4mX7/HLkDFYdSuKt69tN/Ac=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ROokYZOrylZwy3bB7SPHpJLjgaUJ1KQIDpPqF5r2pbSBt91Cxno/JdMvtC8SXxrbf DP6A88iRxM4KZsKWJM5OdpK7EF3cHR3YRxQyv7uMgf1vGbuX9bY5JMxXHPfgJ6zHKx lVeS2cOicbFvax6BeMT4IeOmJm7VnzCI4NwdNHgw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Zqiang , Thomas Gleixner Subject: [PATCH 5.15 141/177] locking/rtmutex: Fix incorrect condition in rtmutex_spin_on_owner() Date: Mon, 20 Dec 2021 15:34:51 +0100 Message-Id: <20211220143044.826704005@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20211220143040.058287525@linuxfoundation.org> References: <20211220143040.058287525@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Zqiang commit 8f556a326c93213927e683fc32bbf5be1b62540a upstream. Optimistic spinning needs to be terminated when the spinning waiter is not longer the top waiter on the lock, but the condition is negated. It terminates if the waiter is the top waiter, which is defeating the whole purpose. Fixes: c3123c431447 ("locking/rtmutex: Dont dereference waiter lockless") Signed-off-by: Zqiang Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20211217074207.77425-1-qiang1.zhang@intel.com Signed-off-by: Greg Kroah-Hartman --- kernel/locking/rtmutex.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1373,7 +1373,7 @@ static bool rtmutex_spin_on_owner(struct * - the VCPU on which owner runs is preempted */ if (!owner->on_cpu || need_resched() || - rt_mutex_waiter_is_top_waiter(lock, waiter) || + !rt_mutex_waiter_is_top_waiter(lock, waiter) || vcpu_is_preempted(task_cpu(owner))) { res = false; break;