From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754224Ab2D1JG1 (ORCPT ); Sat, 28 Apr 2012 05:06:27 -0400 Received: from terminus.zytor.com ([198.137.202.10]:44353 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753277Ab2D1JGV (ORCPT ); Sat, 28 Apr 2012 05:06:21 -0400 Date: Sat, 28 Apr 2012 02:05:03 -0700 From: tip-bot for Thomas Gleixner Message-ID: Cc: mingo@kernel.org, jesper.nilsson@axis.com, rusty@rustcorp.com.au, schwidefsky@de.ibm.com, peterz@infradead.org, cmetcalf@tilera.com, tony.luck@intel.com, ralf@linux-mips.org, linux@arm.linux.org.uk, vapier@gentoo.org, tglx@linutronix.de, venki@google.com, linux-kernel@vger.kernel.org, hpa@zytor.com, richard@nod.at, lethal@linux-sh.org, srivatsa.bhat@linux.vnet.ibm.com, davem@davemloft.net, paulmck@linux.vnet.ibm.com, benh@kernel.crashing.org, dhowells@redhat.com, mattst88@gmail.com, jejb@parisc-linux.org, takata@linux-m32r.org, rkuo@codeaurora.org Reply-To: mingo@kernel.org, jesper.nilsson@axis.com, rusty@rustcorp.com.au, peterz@infradead.org, schwidefsky@de.ibm.com, cmetcalf@tilera.com, tony.luck@intel.com, linux@arm.linux.org.uk, ralf@linux-mips.org, vapier@gentoo.org, tglx@linutronix.de, venki@google.com, linux-kernel@vger.kernel.org, hpa@zytor.com, richard@nod.at, srivatsa.bhat@linux.vnet.ibm.com, lethal@linux-sh.org, davem@davemloft.net, paulmck@linux.vnet.ibm.com, dhowells@redhat.com, benh@kernel.crashing.org, jejb@parisc-linux.org, mattst88@gmail.com, takata@linux-m32r.org, rkuo@codeaurora.org In-Reply-To: <20120420124557.102478630@linutronix.de> References: <20120420124557.102478630@linutronix.de> To: linux-tip-commits@vger.kernel.org Subject: [tip:smp/hotplug] smp: Provide generic idle thread allocation Git-Commit-ID: 29d5e0476e1c4a513859e7858845ad172f560389 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.6 (terminus.zytor.com [127.0.0.1]); Sat, 28 Apr 2012 02:05:09 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 29d5e0476e1c4a513859e7858845ad172f560389 Gitweb: http://git.kernel.org/tip/29d5e0476e1c4a513859e7858845ad172f560389 Author: Thomas Gleixner AuthorDate: Fri, 20 Apr 2012 13:05:45 +0000 Committer: Thomas Gleixner CommitDate: Thu, 26 Apr 2012 12:06:09 +0200 smp: Provide generic idle thread allocation All SMP architectures have magic to fork the idle task and to store it for reusage when cpu hotplug is enabled. Provide a generic infrastructure for it. Create/reinit the idle thread for the cpu which is brought up in the generic code and hand the thread pointer to the architecture code via __cpu_up(). Note, that fork_idle() is called via a workqueue, because this guarantees that the idle thread does not get a reference to a user space VM. This can happen when the boot process did not bring up all possible cpus and a later cpu_up() is initiated via the sysfs interface. In that case fork_idle() would be called in the context of the user space task and take a reference on the user space VM. Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Rusty Russell Cc: Paul E. McKenney Cc: Srivatsa S. Bhat Cc: Matt Turner Cc: Russell King Cc: Mike Frysinger Cc: Jesper Nilsson Cc: Richard Kuo Cc: Tony Luck Cc: Hirokazu Takata Cc: Ralf Baechle Cc: David Howells Cc: James E.J. Bottomley Cc: Benjamin Herrenschmidt Cc: Martin Schwidefsky Cc: Paul Mundt Cc: David S. Miller Cc: Chris Metcalf Cc: Richard Weinberger Cc: x86@kernel.org Acked-by: Venkatesh Pallipadi Link: http://lkml.kernel.org/r/20120420124557.102478630@linutronix.de --- arch/Kconfig | 3 ++ kernel/cpu.c | 2 +- kernel/sched/core.c | 2 + kernel/smpboot.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++- kernel/smpboot.h | 10 ++++++ 5 files changed, 99 insertions(+), 2 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index 684eb5a..4f0d0f7 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -145,6 +145,9 @@ config HAVE_DMA_ATTRS config USE_GENERIC_SMP_HELPERS bool +config GENERIC_SMP_IDLE_THREAD + bool + config HAVE_REGS_AND_STACK_ACCESS_API bool help diff --git a/kernel/cpu.c b/kernel/cpu.c index e58b99a..05c46ba 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -316,7 +316,7 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen) } /* Arch-specific enabling code. */ - ret = __cpu_up(cpu, NULL); + ret = __cpu_up(cpu, idle_thread_get(cpu)); if (ret != 0) goto out_notify; BUG_ON(!cpu_online(cpu)); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 4603b9d..6a63cde 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -83,6 +83,7 @@ #include "sched.h" #include "../workqueue_sched.h" +#include "../smpboot.h" #define CREATE_TRACE_POINTS #include @@ -7049,6 +7050,7 @@ void __init sched_init(void) /* May be allocated at isolcpus cmdline parse time */ if (cpu_isolated_map == NULL) zalloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT); + idle_thread_set_boot_cpu(); #endif init_sched_fair_class(); diff --git a/kernel/smpboot.c b/kernel/smpboot.c index 6dae6a3..ed15769 100644 --- a/kernel/smpboot.c +++ b/kernel/smpboot.c @@ -1,14 +1,96 @@ /* * Common SMP CPU bringup/teardown functions */ +#include +#include #include +#include +#include +#include #include "smpboot.h" +#ifdef CONFIG_GENERIC_SMP_IDLE_THREAD +struct create_idle { + struct work_struct work; + struct task_struct *idle; + struct completion done; + unsigned int cpu; +}; + +static void __cpuinit do_fork_idle(struct work_struct *work) +{ + struct create_idle *c = container_of(work, struct create_idle, work); + + c->idle = fork_idle(c->cpu); + complete(&c->done); +} + +static struct task_struct * __cpuinit idle_thread_create(unsigned int cpu) +{ + struct create_idle c_idle = { + .cpu = cpu, + .done = COMPLETION_INITIALIZER_ONSTACK(c_idle.done), + }; + + INIT_WORK_ONSTACK(&c_idle.work, do_fork_idle); + schedule_work(&c_idle.work); + wait_for_completion(&c_idle.done); + destroy_work_on_stack(&c_idle.work); + return c_idle.idle; +} + +/* + * For the hotplug case we keep the task structs around and reuse + * them. + */ +static DEFINE_PER_CPU(struct task_struct *, idle_threads); + +static inline struct task_struct *get_idle_for_cpu(unsigned int cpu) +{ + struct task_struct *tsk = per_cpu(idle_threads, cpu); + + if (!tsk) + return idle_thread_create(cpu); + init_idle(tsk, cpu); + return tsk; +} + +struct task_struct * __cpuinit idle_thread_get(unsigned int cpu) +{ + return per_cpu(idle_threads, cpu); +} + +void __init idle_thread_set_boot_cpu(void) +{ + per_cpu(idle_threads, smp_processor_id()) = current; +} + +/** + * idle_thread_init - Initialize the idle thread for a cpu + * @cpu: The cpu for which the idle thread should be initialized + * + * Creates the thread if it does not exist. + */ +static int __cpuinit idle_thread_init(unsigned int cpu) +{ + struct task_struct *idle = get_idle_for_cpu(cpu); + + if (IS_ERR(idle)) { + printk(KERN_ERR "failed fork for CPU %u\n", cpu); + return PTR_ERR(idle); + } + per_cpu(idle_threads, cpu) = idle; + return 0; +} +#else +static inline int idle_thread_init(unsigned int cpu) { return 0; } +#endif + /** * smpboot_prepare - generic smpboot preparation */ int __cpuinit smpboot_prepare(unsigned int cpu) { - return 0; + return idle_thread_init(cpu); } diff --git a/kernel/smpboot.h b/kernel/smpboot.h index d88e771..7943bbb 100644 --- a/kernel/smpboot.h +++ b/kernel/smpboot.h @@ -1,6 +1,16 @@ #ifndef SMPBOOT_H #define SMPBOOT_H +struct task_struct; + int smpboot_prepare(unsigned int cpu); +#ifdef CONFIG_GENERIC_SMP_IDLE_THREAD +struct task_struct *idle_thread_get(unsigned int cpu); +void idle_thread_set_boot_cpu(void); +#else +static inline struct task_struct *idle_thread_get(unsigned int cpu) { return NULL; } +static inline void idle_thread_set_boot_cpu(void) { } +#endif + #endif