From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763715AbYDXTkz (ORCPT ); Thu, 24 Apr 2008 15:40:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932133AbYDXTkG (ORCPT ); Thu, 24 Apr 2008 15:40:06 -0400 Received: from pne-smtpout3-sn2.hy.skanova.net ([81.228.8.111]:36794 "EHLO pne-smtpout3-sn2.hy.skanova.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932117AbYDXTkE convert rfc822-to-8bit (ORCPT ); Thu, 24 Apr 2008 15:40:04 -0400 Date: Thu, 24 Apr 2008 22:39:47 +0300 From: Pekka Paalanen To: Ingo Molnar Cc: Pekka Paalanen , Steven Rostedt , linux-kernel@vger.kernel.org, Mathieu Desnoyers Subject: [PATCH v2] x86 mmiotrace: dynamically disable non-boot CPUs Message-ID: <20080424223947.55c053f6@daedalus.pq.iki.fi> In-Reply-To: <20080413230552.33ca587a@daedalus.pq.iki.fi> References: <20080413224207.4430a09c@daedalus.pq.iki.fi> <20080413230552.33ca587a@daedalus.pq.iki.fi> X-Mailer: Claws Mail 3.0.2 (GTK+ 2.12.8; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>From 8979ee55cb6a429c4edd72ebec2244b849f6a79a Mon Sep 17 00:00:00 2001 From: Pekka Paalanen Date: Sat, 12 Apr 2008 00:18:57 +0300 Subject: [PATCH] x86 mmiotrace: dynamically disable non-boot CPUs Mmiotrace is not reliable with multiple CPUs and may miss events. Drop to single CPU when mmiotrace is activated. Signed-off-by: Pekka Paalanen --- I've tested this patch on my Core 2 Duo laptop, and with "[PATCH v2] Check for breakpoint in text_poke to eliminate bug_on" cpu hotplug seems to work fine on a sched-devel/latest SMP kernel both with and without CONFIG_HOTPLUG_CPU. One strange thing was a stack trace printed just before the CPU resets for "shutdown -r now", but I could not see what it was about. I'll ignore that for now, hopefully it's something unrelated. arch/x86/mm/mmio-mod.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 61 insertions(+), 0 deletions(-) diff --git a/arch/x86/mm/mmio-mod.c b/arch/x86/mm/mmio-mod.c index 6d6cac8..1f77d85 100644 --- a/arch/x86/mm/mmio-mod.c +++ b/arch/x86/mm/mmio-mod.c @@ -32,6 +32,7 @@ #include /* for ISA_START_ADDRESS */ #include #include +#include #include "pf_in.h" @@ -400,6 +401,64 @@ static void clear_trace_list(void) } } +#ifdef CONFIG_HOTPLUG_CPU +static cpumask_t downed_cpus; + +static void enter_uniprocessor(void) +{ + int cpu; + int err; + + get_online_cpus(); + downed_cpus = cpu_online_map; + cpu_clear(first_cpu(cpu_online_map), downed_cpus); + if (num_online_cpus() > 1) + pr_notice(NAME "Disabling non-boot CPUs...\n"); + put_online_cpus(); + + for_each_cpu_mask(cpu, downed_cpus) { + err = cpu_down(cpu); + if (!err) { + pr_info(NAME "CPU%d is down.\n", cpu); + } else { + pr_err(NAME "Error taking CPU%d down: %d\n", cpu, err); + } + } + if (num_online_cpus() > 1) + pr_warning(NAME "multiple CPUs still online, " + "may miss events.\n"); +} + +static void leave_uniprocessor(void) +{ + int cpu; + int err; + + if (cpus_weight(downed_cpus) == 0) + return; + pr_notice(NAME "Re-enabling CPUs...\n"); + for_each_cpu_mask(cpu, downed_cpus) { + err = cpu_up(cpu); + if (!err) + pr_info(NAME "enabled CPU%d.\n", cpu); + else + pr_err(NAME "cannot re-enable CPU%d: %d\n", cpu, err); + } +} + +#else /* !CONFIG_HOTPLUG_CPU */ +static void enter_uniprocessor(void) +{ + if (num_online_cpus() > 1) + pr_warning(NAME "multiple CPUs are online, may miss events. " + "Suggest booting with maxcpus=1 kernel argument.\n"); +} + +static void leave_uniprocessor(void) +{ +} +#endif + #if 0 /* XXX: out of order */ static struct file_operations fops_marker = { .owner = THIS_MODULE, @@ -422,6 +481,7 @@ void enable_mmiotrace(void) if (nommiotrace) pr_info(NAME "MMIO tracing disabled.\n"); + enter_uniprocessor(); spin_lock_irq(&trace_lock); atomic_inc(&mmiotrace_enabled); spin_unlock_irq(&trace_lock); @@ -442,6 +502,7 @@ void disable_mmiotrace(void) spin_unlock_irq(&trace_lock); clear_trace_list(); /* guarantees: no more kmmio callbacks */ + leave_uniprocessor(); if (marker_file) { debugfs_remove(marker_file); marker_file = NULL; -- 1.5.3.7