Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756421Ab1BJM0x (ORCPT ); Thu, 10 Feb 2011 07:26:53 -0500 Received: from cantor.suse.de ([195.135.220.2]:33779 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756290Ab1BJMZU (ORCPT ); Thu, 10 Feb 2011 07:25:20 -0500 From: stable-bot for Venkatesh Pallipadi Date: Thu, 10 Feb 2011 10:23:28 +0100 Subject: [PATCH 21/28] sched: Call tick_check_idle before __irq_enter To: stable@kernel.org Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar Message-ID: <1297340644.5512.21.camel@marge.simson.net> Mime-Version: 1.0 X-Mailer: Evolution 2.30.1.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2647 Lines: 81 Commit: d267f87fb8179c6dba03d08b91952e81bc3723c7 upstream Author: Venkatesh Pallipadi AuthorDate: Mon Oct 4 17:03:23 2010 -0700 When CPU is idle and on first interrupt, irq_enter calls tick_check_idle() to notify interruption from idle. But, there is a problem if this call is done after __irq_enter, as all routines in __irq_enter may find stale time due to yet to be done tick_check_idle. Specifically, trace calls in __irq_enter when they use global clock and also account_system_vtime change in this patch as it wants to use sched_clock_cpu() to do proper irq timing. But, tick_check_idle was moved after __irq_enter intentionally to prevent problem of unneeded ksoftirqd wakeups by the commit ee5f80a: irq: call __irq_enter() before calling the tick_idle_check Impact: avoid spurious ksoftirqd wakeups Moving tick_check_idle() before __irq_enter and wrapping it with local_bh_enable/disable would solve both the problems. Fixed-by: Yong Zhang Signed-off-by: Venkatesh Pallipadi Signed-off-by: Peter Zijlstra LKML-Reference: <1286237003-12406-9-git-send-email-venki@google.com> Signed-off-by: Ingo Molnar Signed-off-by: Mike Galbraith Acked-by: Peter Zijlstra --- kernel/sched.c | 2 +- kernel/softirq.c | 12 +++++++++--- 2 files changed, 10 insertions(+), 4 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index 4f86094..c7f69fe 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -1872,8 +1872,8 @@ void account_system_vtime(struct task_struct *curr) local_irq_save(flags); - now = sched_clock(); cpu = smp_processor_id(); + now = sched_clock_cpu(cpu); delta = now - per_cpu(irq_start_time, cpu); per_cpu(irq_start_time, cpu) = now; /* diff --git a/kernel/softirq.c b/kernel/softirq.c index 0a617de..04a0252 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -296,10 +296,16 @@ void irq_enter(void) rcu_irq_enter(); if (idle_cpu(cpu) && !in_interrupt()) { - __irq_enter(); + /* + * Prevent raise_softirq from needlessly waking up ksoftirqd + * here, as softirq will be serviced on return from interrupt. + */ + local_bh_disable(); tick_check_idle(cpu); - } else - __irq_enter(); + _local_bh_enable(); + } + + __irq_enter(); } #ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED -- 1.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/