Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752173AbcLFCch (ORCPT ); Mon, 5 Dec 2016 21:32:37 -0500 Received: from mail-wj0-f195.google.com ([209.85.210.195]:34597 "EHLO mail-wj0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752003AbcLFCcd (ORCPT ); Mon, 5 Dec 2016 21:32:33 -0500 From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Tony Luck , Wanpeng Li , Peter Zijlstra , Michael Ellerman , Heiko Carstens , Benjamin Herrenschmidt , Thomas Gleixner , Paul Mackerras , Ingo Molnar , Fenghua Yu , Rik van Riel , Martin Schwidefsky , Stanislaw Gruszka Subject: [FIX][PATCH 01/10] powerpc32: Fix stale scaled stime on context switch Date: Tue, 6 Dec 2016 03:32:14 +0100 Message-Id: <1480991543-6557-2-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1480991543-6557-1-git-send-email-fweisbec@gmail.com> References: <1480991543-6557-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1738 Lines: 47 On context switch with powerpc32, the cputime is accumulated in the thread_info struct. So the switching-in task must move forward its start time snapshot to the current time in order to later compute the delta spent in system mode. This is what we do for the normal cputime by initializing the starttime field to the value of the previous task's starttime which got freshly updated. But we are missing the update of the scaled cputime start time. As a result we may be accounting too much scaled cputime later. Fix this by initializing the scaled cputime the same way we do for normal cputime. Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: Heiko Carstens Cc: Martin Schwidefsky Cc: Tony Luck Cc: Fenghua Yu Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Stanislaw Gruszka Cc: Wanpeng Li Signed-off-by: Frederic Weisbecker --- arch/powerpc/kernel/time.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index be9751f..bca2781 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -407,6 +407,7 @@ void arch_vtime_task_switch(struct task_struct *prev) struct cpu_accounting_data *acct = get_accounting(current); acct->starttime = get_accounting(prev)->starttime; + acct->startspurr = get_accounting(prev)->startspurr; acct->system_time = 0; acct->user_time = 0; } -- 2.7.4