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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 <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Cc: Matt Turner <mattst88@gmail.com> Cc: Russell King <linux@arm.linux.org.uk> Cc: Mike Frysinger <vapier@gentoo.org> Cc: Jesper Nilsson <jesper.nilsson@axis.com> Cc: Richard Kuo <rkuo@codeaurora.org> Cc: Tony Luck <tony.luck@intel.com> Cc: Hirokazu Takata <takata@linux-m32r.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: David Howells <dhowells@redhat.com> Cc: James E.J. Bottomley <jejb@parisc-linux.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Paul Mundt <lethal@linux-sh.org> Cc: David S. Miller <davem@davemloft.net> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Richard Weinberger <richard@nod.at> Cc: x86@kernel.org Acked-by: Venkatesh Pallipadi <venki@google.com> Link: http://lkml.kernel.org/r/20120420124557.102478630@linutronix.de
97 lines
2.1 KiB
C
97 lines
2.1 KiB
C
/*
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* Common SMP CPU bringup/teardown functions
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*/
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#include <linux/err.h>
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#include <linux/smp.h>
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#include <linux/init.h>
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#include <linux/sched.h>
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#include <linux/percpu.h>
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#include <linux/workqueue.h>
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#include "smpboot.h"
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#ifdef CONFIG_GENERIC_SMP_IDLE_THREAD
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struct create_idle {
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struct work_struct work;
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struct task_struct *idle;
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struct completion done;
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unsigned int cpu;
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};
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static void __cpuinit do_fork_idle(struct work_struct *work)
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{
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struct create_idle *c = container_of(work, struct create_idle, work);
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c->idle = fork_idle(c->cpu);
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complete(&c->done);
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}
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static struct task_struct * __cpuinit idle_thread_create(unsigned int cpu)
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{
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struct create_idle c_idle = {
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.cpu = cpu,
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.done = COMPLETION_INITIALIZER_ONSTACK(c_idle.done),
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};
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INIT_WORK_ONSTACK(&c_idle.work, do_fork_idle);
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schedule_work(&c_idle.work);
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wait_for_completion(&c_idle.done);
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destroy_work_on_stack(&c_idle.work);
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return c_idle.idle;
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}
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/*
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* For the hotplug case we keep the task structs around and reuse
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* them.
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*/
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static DEFINE_PER_CPU(struct task_struct *, idle_threads);
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static inline struct task_struct *get_idle_for_cpu(unsigned int cpu)
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{
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struct task_struct *tsk = per_cpu(idle_threads, cpu);
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if (!tsk)
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return idle_thread_create(cpu);
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init_idle(tsk, cpu);
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return tsk;
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}
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struct task_struct * __cpuinit idle_thread_get(unsigned int cpu)
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{
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return per_cpu(idle_threads, cpu);
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}
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void __init idle_thread_set_boot_cpu(void)
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{
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per_cpu(idle_threads, smp_processor_id()) = current;
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}
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/**
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* idle_thread_init - Initialize the idle thread for a cpu
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* @cpu: The cpu for which the idle thread should be initialized
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*
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* Creates the thread if it does not exist.
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*/
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static int __cpuinit idle_thread_init(unsigned int cpu)
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{
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struct task_struct *idle = get_idle_for_cpu(cpu);
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if (IS_ERR(idle)) {
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printk(KERN_ERR "failed fork for CPU %u\n", cpu);
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return PTR_ERR(idle);
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}
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per_cpu(idle_threads, cpu) = idle;
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return 0;
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}
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#else
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static inline int idle_thread_init(unsigned int cpu) { return 0; }
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#endif
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/**
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* smpboot_prepare - generic smpboot preparation
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*/
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int __cpuinit smpboot_prepare(unsigned int cpu)
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{
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return idle_thread_init(cpu);
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}
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