Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755711Ab1FGATN (ORCPT ); Mon, 6 Jun 2011 20:19:13 -0400 Received: from hera.kernel.org ([140.211.167.34]:39947 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752798Ab1FGATM (ORCPT ); Mon, 6 Jun 2011 20:19:12 -0400 Date: Tue, 7 Jun 2011 00:19:04 GMT From: tip-bot for Suresh Siddha Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, suresh.b.siddha@intel.com, tglx@linutronix.de, hpa@linux.intel.com Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, suresh.b.siddha@intel.com, tglx@linutronix.de, hpa@linux.intel.com In-Reply-To: <20110606231752.023885847@sbsiddha-MOBL3.sc.intel.com> References: <20110606231752.023885847@sbsiddha-MOBL3.sc.intel.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86, stop_machine: Enable __stop_machine() to be called from the cpu online path Git-Commit-ID: e9de5210f6a6a8b403035985b5a65e77e7004690 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Tue, 07 Jun 2011 00:19:05 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5628 Lines: 160 Commit-ID: e9de5210f6a6a8b403035985b5a65e77e7004690 Gitweb: http://git.kernel.org/tip/e9de5210f6a6a8b403035985b5a65e77e7004690 Author: Suresh Siddha AuthorDate: Mon, 6 Jun 2011 16:16:56 -0700 Committer: H. Peter Anvin CommitDate: Mon, 6 Jun 2011 16:42:09 -0700 x86, stop_machine: Enable __stop_machine() to be called from the cpu online path Currently stop machine infrastructure can be called only from a cpu that is online. But for !CONFIG_SMP, we do allow calling __stop_machine() before the cpu is online. x86 for example requires stop machine infrastructure in the cpu online path and currently implements its own stop machine (using stop_one_cpu_nowait()) for MTRR initialization in the cpu online path. Enhance the __stop_machine() so that it can be called before the cpu is onlined. This will pave the way for code consolidation and address potential deadlocks caused by multiple mechanisms of doing system wide rendezvous. This will also address the behavioral differences of __stop_machine() between SMP and UP builds. Signed-off-by: Suresh Siddha Link: http://lkml.kernel.org/r/20110606231752.023885847@sbsiddha-MOBL3.sc.intel.com Cc: stable@kernel.org # v2.6.35+ Signed-off-by: H. Peter Anvin --- kernel/stop_machine.c | 62 +++++++++++++++++++++++++++++++++++++++++++++---- 1 files changed, 57 insertions(+), 5 deletions(-) diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index e3516b2..c78b0c2 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -136,12 +136,35 @@ void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg, static DEFINE_MUTEX(stop_cpus_mutex); static DEFINE_PER_CPU(struct cpu_stop_work, stop_cpus_work); +/** + * __stop_cpus - stop multiple cpus + * @cpumask: cpus to stop + * @fn: function to execute + * @arg: argument to @fn + * + * Execute @fn(@arg) on online cpus in @cpumask. If @cpumask is NULL, @fn + * is run on all the online cpus including the current cpu (even if it + * is not online). + * On each target cpu, @fn is run in a process context (except when run on + * the cpu that is in the process of coming online, in which case @fn is run + * in the same context as __stop_cpus()) with the highest priority + * preempting any task on the cpu and monopolizing it. This function + * returns after all executions are complete. + */ int __stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg) { + int online = cpu_online(smp_processor_id()); + int include_this_offline = 0; struct cpu_stop_work *work; struct cpu_stop_done done; + unsigned int weight; unsigned int cpu; + if (!cpumask) { + cpumask = cpu_online_mask; + include_this_offline = 1; + } + /* initialize works and done */ for_each_cpu(cpu, cpumask) { work = &per_cpu(stop_cpus_work, cpu); @@ -149,7 +172,12 @@ int __stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg) work->arg = arg; work->done = &done; } - cpu_stop_init_done(&done, cpumask_weight(cpumask)); + + weight = cpumask_weight(cpumask); + if (!online && include_this_offline) + weight++; + + cpu_stop_init_done(&done, weight); /* * Disable preemption while queueing to avoid getting @@ -162,7 +190,20 @@ int __stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg) &per_cpu(stop_cpus_work, cpu)); preempt_enable(); - wait_for_completion(&done.completion); + if (online) + wait_for_completion(&done.completion); + else { + /* + * This cpu is not yet online. If @fn needs to be run on this + * cpu, run it now. Also, we can't afford to sleep here, + * so poll till the work is completed on all the cpu's. + */ + if (include_this_offline) + fn(arg); + while (atomic_read(&done.nr_todo) > 1) + cpu_relax(); + } + return done.executed ? done.ret : -ENOENT; } @@ -431,6 +472,7 @@ static int stop_machine_cpu_stop(void *data) struct stop_machine_data *smdata = data; enum stopmachine_state curstate = STOPMACHINE_NONE; int cpu = smp_processor_id(), err = 0; + unsigned long flags = 0; bool is_active; if (!smdata->active_cpus) @@ -446,7 +488,7 @@ static int stop_machine_cpu_stop(void *data) curstate = smdata->state; switch (curstate) { case STOPMACHINE_DISABLE_IRQ: - local_irq_disable(); + local_irq_save(flags); hard_irq_disable(); break; case STOPMACHINE_RUN: @@ -460,7 +502,7 @@ static int stop_machine_cpu_stop(void *data) } } while (curstate != STOPMACHINE_EXIT); - local_irq_enable(); + local_irq_restore(flags); return err; } @@ -470,9 +512,19 @@ int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus) .num_threads = num_online_cpus(), .active_cpus = cpus }; + /* Include the calling cpu that might not be online yet. */ + if (!cpu_online(smp_processor_id())) + smdata.num_threads++; + /* 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); + + if (cpu_online(smp_processor_id())) + return stop_cpus(cpu_online_mask, stop_machine_cpu_stop, + &smdata); + else + return __stop_cpus(NULL, stop_machine_cpu_stop, + &smdata); } int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus) -- 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/