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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 2BD43C432C2 for ; Wed, 25 Sep 2019 21:42:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F107B20872 for ; Wed, 25 Sep 2019 21:42:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1569447773; bh=AYode9PlaIC0hRrFA8rWwBDwtULCuvtmK+Py1GKxgD4=; h=From:To:Cc:Subject:Date:List-ID:From; b=S5gXK60dLejovcz/Bbv2dX4YsU9c2ZzaH9EYjP0VrqNOLeaA7kD180Zl0XO7gizw1 sZnpLPvBYBbWv7LO+acFYbHBIMY6aEur/YNntdwPlCwTmllEhJHaB91wT2lQCGRZVw D2AI0EXT8TV0rE+qukZD9Rs0MVv5XW/WhWQNh5AM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727664AbfIYVmw (ORCPT ); Wed, 25 Sep 2019 17:42:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:49914 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726173AbfIYVmw (ORCPT ); Wed, 25 Sep 2019 17:42:52 -0400 Received: from lenoir.home (lfbn-ncy-1-150-155.w83-194.abo.wanadoo.fr [83.194.232.155]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 934A3205F4; Wed, 25 Sep 2019 21:42:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1569447771; bh=AYode9PlaIC0hRrFA8rWwBDwtULCuvtmK+Py1GKxgD4=; h=From:To:Cc:Subject:Date:From; b=H7GatfJ063qpvrFS9alZimCNtMI9haZyoVnLX19hvI5oDk9Mi4l+gmWTtLUYaluLt /D7Q/A6wTAyXuMJde37ySUsE1tU+Ke9YTAcQFvVWyxuJJr1cpyPZKu2xqCc7PrKNVL /OQ5XIcgOmk1yXhoC3RYcZSZuSF+rr0qH09heoaM= From: Frederic Weisbecker To: Peter Zijlstra , Ingo Molnar Cc: LKML , Frederic Weisbecker , Wanpeng Li , Thomas Gleixner , Rik van Riel Subject: [PATCH] sched/vtime: Fix guest/system mis-accounting on task switch Date: Wed, 25 Sep 2019 23:42:42 +0200 Message-Id: <20190925214242.21873-1-frederic@kernel.org> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Fixes: 2a42eb9594a1 ("sched/cputime: Accumulate vtime on top of nsec clocksource") Signed-off-by: Frederic Weisbecker Cc: Thomas Gleixner Cc: Rik van Riel Cc: Peter Zijlstra Cc: Wanpeng Li Cc: Ingo Molnar --- 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 2305ce89a26c..46ed4e1383e2 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); -- 2.21.0