Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751835AbdHAES7 (ORCPT ); Tue, 1 Aug 2017 00:18:59 -0400 Received: from mail-pf0-f179.google.com ([209.85.192.179]:34556 "EHLO mail-pf0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751779AbdHAES6 (ORCPT ); Tue, 1 Aug 2017 00:18:58 -0400 From: Andres Oportus To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Wanpeng Li , "Peter Zijlstra (Intel)" , Frederic Weisbecker , Linus Torvalds , Mike Galbraith , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Rik van Riel , Thomas Gleixner , Ingo Molnar , Greg Kroah-Hartman , Andres Oportus Subject: [stable 4.4: PATCH] sched/cputime: Fix prev steal time accouting during CPU hotplug Date: Mon, 31 Jul 2017 21:18:00 -0700 Message-Id: <1501561080-3459-1-git-send-email-andresoportus@android.com> X-Mailer: git-send-email 1.9.1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2563 Lines: 74 commit 3d89e5478bf550a50c99e93adf659369798263b0 upstream. Commit: e9532e69b8d1 ("sched/cputime: Fix steal time accounting vs. CPU hotplug") ... set rq->prev_* to 0 after a CPU hotplug comes back, in order to fix the case where (after CPU hotplug) steal time is smaller than rq->prev_steal_time. However, this should never happen. Steal time was only smaller because of the KVM-specific bug fixed by the previous patch. Worse, the previous patch triggers a bug on CPU hot-unplug/plug operation: because rq->prev_steal_time is cleared, all of the CPU's past steal time will be accounted again on hot-plug. Since the root cause has been fixed, we can just revert commit e9532e69b8d1 ("sched/cputime: Fix steal time accounting vs. CPU hotplug"). Signed-off-by: Wanpeng Li Signed-off-by: Peter Zijlstra (Intel) Acked-by: Paolo Bonzini Cc: Frederic Weisbecker Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Radim Krčmář Cc: Rik van Riel Cc: Thomas Gleixner Fixes: 'commit e9532e69b8d1 ("sched/cputime: Fix steal time accounting vs. CPU hotplug")' Link: http://lkml.kernel.org/r/1465813966-3116-3-git-send-email-wanpeng.li@hotmail.com Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman Signed-off-by: Andres Oportus --- kernel/sched/core.c | 1 - kernel/sched/sched.h | 13 ------------- 2 files changed, 14 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index c436426..b103b9c 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5553,7 +5553,6 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu) case CPU_UP_PREPARE: rq->calc_load_update = calc_load_update; - account_reset_rq(rq); break; case CPU_ONLINE: diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 4e5db65..55d92a1 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1770,16 +1770,3 @@ static inline u64 irq_time_read(int cpu) } #endif /* CONFIG_64BIT */ #endif /* CONFIG_IRQ_TIME_ACCOUNTING */ - -static inline void account_reset_rq(struct rq *rq) -{ -#ifdef CONFIG_IRQ_TIME_ACCOUNTING - rq->prev_irq_time = 0; -#endif -#ifdef CONFIG_PARAVIRT - rq->prev_steal_time = 0; -#endif -#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING - rq->prev_steal_time_rq = 0; -#endif -} -- 1.9.1