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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 D39A4C433ED for ; Mon, 10 May 2021 12:37:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B88F16128E for ; Mon, 10 May 2021 12:37:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347317AbhEJMdx (ORCPT ); Mon, 10 May 2021 08:33:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:49986 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232879AbhEJLLz (ORCPT ); Mon, 10 May 2021 07:11:55 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7EDDF6193A; Mon, 10 May 2021 11:09:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1620644983; bh=kwOyVJpLtd8gheGbQRqdFlIORGINOYnXM+3NvNS/wfs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=y6aEp0X36dpTMoRmBa4IDRLWX9gx4pv5Yb6GfQBCE9ECiEuQyXRRQce82tbNs5Adu cxxa3B4FTM9j48EzX9DgOSZiCAQbTaRHJ+c37Up6hQ4tY5cPLqTp2v0E9R+szUeQ+2 0qStWgfIruKRKYnwZUV+11E3VsO32yZTntWYZ93U= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Charan Teja Reddy , "Peter Zijlstra (Intel)" , Johannes Weiner , Sasha Levin Subject: [PATCH 5.12 268/384] sched,psi: Handle potential task count underflow bugs more gracefully Date: Mon, 10 May 2021 12:20:57 +0200 Message-Id: <20210510102023.682497731@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210510102014.849075526@linuxfoundation.org> References: <20210510102014.849075526@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: Charan Teja Reddy [ Upstream commit 9d10a13d1e4c349b76f1c675a874a7f981d6d3b4 ] psi_group_cpu->tasks, represented by the unsigned int, stores the number of tasks that could be stalled on a psi resource(io/mem/cpu). Decrementing these counters at zero leads to wrapping which further leads to the psi_group_cpu->state_mask is being set with the respective pressure state. This could result into the unnecessary time sampling for the pressure state thus cause the spurious psi events. This can further lead to wrong actions being taken at the user land based on these psi events. Though psi_bug is set under these conditions but that just for debug purpose. Fix it by decrementing the ->tasks count only when it is non-zero. Signed-off-by: Charan Teja Reddy Signed-off-by: Peter Zijlstra (Intel) Acked-by: Johannes Weiner Link: https://lkml.kernel.org/r/1618585336-37219-1-git-send-email-charante@codeaurora.org Signed-off-by: Sasha Levin --- kernel/sched/psi.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index 967732c0766c..651218ded981 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -711,14 +711,15 @@ static void psi_group_change(struct psi_group *group, int cpu, for (t = 0, m = clear; m; m &= ~(1 << t), t++) { if (!(m & (1 << t))) continue; - if (groupc->tasks[t] == 0 && !psi_bug) { + if (groupc->tasks[t]) { + groupc->tasks[t]--; + } else if (!psi_bug) { printk_deferred(KERN_ERR "psi: task underflow! cpu=%d t=%d tasks=[%u %u %u %u] clear=%x set=%x\n", cpu, t, groupc->tasks[0], groupc->tasks[1], groupc->tasks[2], groupc->tasks[3], clear, set); psi_bug = 1; } - groupc->tasks[t]--; } for (t = 0; set; set &= ~(1 << t), t++) -- 2.30.2