From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933145Ab1JDTSO (ORCPT ); Tue, 4 Oct 2011 15:18:14 -0400 Received: from claw.goop.org ([74.207.240.146]:56713 "EHLO claw.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932539Ab1JDTSN (ORCPT ); Tue, 4 Oct 2011 15:18:13 -0400 From: Jeremy Fitzhardinge To: Steven Rostedt Cc: "David S. Miller" , David Daney , Michael Ellerman , Jan Glauber , Jason Baron , the arch/x86 maintainers , Xen Devel , Linux Kernel Mailing List , Jeremy Fitzhardinge , Rusty Russell , Peter Zijlstra , Andrew Morton , "H. Peter Anvin" , Ingo Molnar Subject: [PATCH RFC V3 2/8] stop_machine: make stop_machine safe and efficient to call early Date: Tue, 4 Oct 2011 12:18:03 -0700 Message-Id: <619c66d6da63aa086e2eac017e7aed216cc8ddc3.1317755691.git.jeremy.fitzhardinge@citrix.com> X-Mailer: git-send-email 1.7.6.4 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jeremy Fitzhardinge Make stop_machine() safe to call early in boot, before stop_machine() has been set up, by simply calling the callback function directly if there's only one CPU online. [ Fixes from AKPM: - add comment - local_irq_flags, not save_flags - also call hard_irq_disable() for systems which need it Tejun suggested using an explicit flag rather than just looking at the online cpu count. ] Signed-off-by: Jeremy Fitzhardinge Acked-by: Tejun Heo Cc: Rusty Russell Cc: Peter Zijlstra Cc: Andrew Morton Cc: H. Peter Anvin Cc: Ingo Molnar Cc: Steven Rostedt --- kernel/stop_machine.c | 22 ++++++++++++++++++++++ 1 files changed, 22 insertions(+), 0 deletions(-) diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index ba5070c..d3f960a 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -41,6 +41,7 @@ struct cpu_stopper { }; static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper); +static bool stop_machine_initialized = false; static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo) { @@ -386,6 +387,8 @@ static int __init cpu_stop_init(void) cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_ONLINE, bcpu); register_cpu_notifier(&cpu_stop_cpu_notifier); + stop_machine_initialized = true; + return 0; } early_initcall(cpu_stop_init); @@ -485,6 +488,25 @@ int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus) .num_threads = num_online_cpus(), .active_cpus = cpus }; + if (!stop_machine_initialized) { + /* + * Handle the case where stop_machine() is called + * early in boot before stop_machine() has been + * initialized. + */ + unsigned long flags; + int ret; + + WARN_ON_ONCE(smdata.num_threads != 1); + + local_irq_save(flags); + hard_irq_disable(); + ret = (*fn)(data); + local_irq_restore(flags); + + return ret; + } + /* Set the initial state and stop all online cpus. */ set_state(&smdata, STOPMACHINE_PREPARE); return stop_cpus(cpu_online_mask, stop_machine_cpu_stop, &smdata); -- 1.7.6.4