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=ham 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 8204CCA9EC9 for ; Mon, 4 Nov 2019 21:55:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 56BC321E6F for ; Mon, 4 Nov 2019 21:55:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572904503; bh=ovT+YY6J3EIP56Anwt7CNtWnyGZ15befber1YB3kycw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ewI6HcqJn9VyOe+p1uoPmkBps0EFI+69rTAw4db15W6iLHYzG1UpQ+F8SYfc1JXCJ sd/nbkgYx0BZW5EcWE6dM51QD5lE5TyJP/QxqvV5zb08GM/sfDthvCWtBf8m64S2G8 Vraf4xkF5dFajz3apu/Z92Aq4KIqWxwBZpvR/DT8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388073AbfKDVzC (ORCPT ); Mon, 4 Nov 2019 16:55:02 -0500 Received: from mail.kernel.org ([198.145.29.99]:50012 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387550AbfKDVy7 (ORCPT ); Mon, 4 Nov 2019 16:54:59 -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 4BB272184C; Mon, 4 Nov 2019 21:54:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572904497; bh=ovT+YY6J3EIP56Anwt7CNtWnyGZ15befber1YB3kycw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=smm9BVFiT6XB6YITUoFmiBFRVwf+r26EB+JPCLYXctIUeR4i4JjTd4yKO9nDkjipU IHlt8vuZKT7mtyCvLlLfqOwfTga8SlAqkZBWMHOKCAG2a2BejmllOLt1WHcwq8rOWc hDxjW/9LAxjmmNcM5EDxmaWjmKU5mkHjmQzH7Tjs= 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 4.14 49/95] sched/vtime: Fix guest/system mis-accounting on task switch Date: Mon, 4 Nov 2019 22:44:47 +0100 Message-Id: <20191104212103.626150804@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191104212038.056365853@linuxfoundation.org> References: <20191104212038.056365853@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 14d2dbf97c531..45c2cd37fe6b0 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -738,7 +738,7 @@ 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); @@ -781,7 +781,7 @@ 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); @@ -792,7 +792,7 @@ 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