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,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 E809BCA9ED3 for ; Mon, 4 Nov 2019 22:06:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BCF4F222C4 for ; Mon, 4 Nov 2019 22:06:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572905217; bh=NynUHA4qevW95zKm+h3K9YX279or91FM4C/MRJ+5jkI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=IRCBlNSVn8qSA8Mwvmp8kZAERpxTemKljENfhbJZ69LmLFWtp/DTEak3Z/pxWegRe iAtCWI+2Z6S34IaSbTtzGeNCDXKVuLkRi3FoXZaBV9rodkjdCm5a5jypEni9wqBNY/ Ioiwd9o5AShvGhRYtQD2Efyx7dq3jxtmOBCwOisg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390017AbfKDWG4 (ORCPT ); Mon, 4 Nov 2019 17:06:56 -0500 Received: from mail.kernel.org ([198.145.29.99]:38960 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389069AbfKDWGu (ORCPT ); Mon, 4 Nov 2019 17:06:50 -0500 Received: from localhost (6.204-14-84.ripe.coltfrance.com [84.14.204.6]) (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 C2E3D21D71; Mon, 4 Nov 2019 22:06:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572905209; bh=NynUHA4qevW95zKm+h3K9YX279or91FM4C/MRJ+5jkI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zuz8B4qJhICFmXIc51xB7+GtOlnxMVTwlS06rLk+msKIB5LmV7R3YSkj2wUdEZzJk atFGiINUQRBQP7sEnCxpIMT6KgjPkPxb9WOR04hPSnEvyiX53eAngUarwjo84+8TwH vdEPcG/FElaWQrczpKFdmAIbg9fe21APu4zZQKVw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Frederic Weisbecker , "Peter Zijlstra (Intel)" , Linus Torvalds , Rik van Riel , Thomas Gleixner , Wanpeng Li , Ingo Molnar , Sasha Levin Subject: [PATCH 5.3 066/163] sched/vtime: Fix guest/system mis-accounting on task switch Date: Mon, 4 Nov 2019 22:44:16 +0100 Message-Id: <20191104212144.767062618@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191104212140.046021995@linuxfoundation.org> References: <20191104212140.046021995@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Frederic Weisbecker [ Upstream commit 68e7a4d66b0ce04bf18ff2ffded5596ab3618585 ] vtime_account_system() assumes that the target task to account cputime to is always the current task. This is most often true indeed except on task switch where we call: vtime_common_task_switch(prev) vtime_account_system(prev) Here prev is the scheduling-out task where we account the cputime to. It doesn't match current that is already the scheduling-in task at this stage of the context switch. So we end up checking the wrong task flags to determine if we are accounting guest or system time to the previous task. As a result the wrong task is used to check if the target is running in guest mode. We may then spuriously account or leak either system or guest time on task switch. Fix this assumption and also turn vtime_guest_enter/exit() to use the task passed in parameter as well to avoid future similar issues. Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: Wanpeng Li Fixes: 2a42eb9594a1 ("sched/cputime: Accumulate vtime on top of nsec clocksource") Link: https://lkml.kernel.org/r/20190925214242.21873-1-frederic@kernel.org Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin --- kernel/sched/cputime.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 2305ce89a26cf..46ed4e1383e21 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -740,7 +740,7 @@ void vtime_account_system(struct task_struct *tsk) write_seqcount_begin(&vtime->seqcount); /* We might have scheduled out from guest path */ - if (current->flags & PF_VCPU) + if (tsk->flags & PF_VCPU) vtime_account_guest(tsk, vtime); else __vtime_account_system(tsk, vtime); @@ -783,7 +783,7 @@ void vtime_guest_enter(struct task_struct *tsk) */ write_seqcount_begin(&vtime->seqcount); __vtime_account_system(tsk, vtime); - current->flags |= PF_VCPU; + tsk->flags |= PF_VCPU; write_seqcount_end(&vtime->seqcount); } EXPORT_SYMBOL_GPL(vtime_guest_enter); @@ -794,7 +794,7 @@ void vtime_guest_exit(struct task_struct *tsk) write_seqcount_begin(&vtime->seqcount); vtime_account_guest(tsk, vtime); - current->flags &= ~PF_VCPU; + tsk->flags &= ~PF_VCPU; write_seqcount_end(&vtime->seqcount); } EXPORT_SYMBOL_GPL(vtime_guest_exit); -- 2.20.1