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    Subject[patch 06/18] x86: Use generic idle thread allocation
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: x86@kernel.org
    Cc: Jeremy Fitzhardinge <jeremy@goop.org>
    ---
    arch/x86/Kconfig | 1
    arch/x86/include/asm/smp.h | 1
    arch/x86/kernel/smpboot.c | 81 +++++----------------------------------------
    arch/x86/xen/smp.c | 15 +-------
    4 files changed, 14 insertions(+), 84 deletions(-)

    Index: linux-2.6/arch/x86/Kconfig
    ===================================================================
    --- linux-2.6.orig/arch/x86/Kconfig
    +++ linux-2.6/arch/x86/Kconfig
    @@ -82,6 +82,7 @@ config X86
    select ARCH_HAVE_NMI_SAFE_CMPXCHG
    select GENERIC_IOMAP
    select DCACHE_WORD_ACCESS if !DEBUG_PAGEALLOC
    + select GENERIC_SMP_IDLE_THREAD

    config INSTRUCTION_DECODER
    def_bool (KPROBES || PERF_EVENTS)
    Index: linux-2.6/arch/x86/include/asm/smp.h
    ===================================================================
    --- linux-2.6.orig/arch/x86/include/asm/smp.h
    +++ linux-2.6/arch/x86/include/asm/smp.h
    @@ -164,6 +164,7 @@ int wbinvd_on_all_cpus(void);

    void native_send_call_func_ipi(const struct cpumask *mask);
    void native_send_call_func_single_ipi(int cpu);
    +void x86_idle_thread_init(unsigned int cpu, struct task_struct *idle);

    void smp_store_cpu_info(int id);
    #define cpu_physical_id(cpu) per_cpu(x86_cpu_to_apicid, cpu)
    Index: linux-2.6/arch/x86/kernel/smpboot.c
    ===================================================================
    --- linux-2.6.orig/arch/x86/kernel/smpboot.c
    +++ linux-2.6/arch/x86/kernel/smpboot.c
    @@ -76,20 +76,8 @@
    /* State of each CPU */
    DEFINE_PER_CPU(int, cpu_state) = { 0 };

    -/* Store all idle threads, this can be reused instead of creating
    -* a new thread. Also avoids complicated thread destroy functionality
    -* for idle threads.
    -*/
    #ifdef CONFIG_HOTPLUG_CPU
    /*
    - * Needed only for CONFIG_HOTPLUG_CPU because __cpuinitdata is
    - * removed after init for !CONFIG_HOTPLUG_CPU.
    - */
    -static DEFINE_PER_CPU(struct task_struct *, idle_thread_array);
    -#define get_idle_for_cpu(x) (per_cpu(idle_thread_array, x))
    -#define set_idle_for_cpu(x, p) (per_cpu(idle_thread_array, x) = (p))
    -
    -/*
    * We need this for trampoline_base protection from concurrent accesses when
    * off- and onlining cores wildly.
    */
    @@ -97,20 +85,16 @@ static DEFINE_MUTEX(x86_cpu_hotplug_driv

    void cpu_hotplug_driver_lock(void)
    {
    - mutex_lock(&x86_cpu_hotplug_driver_mutex);
    + mutex_lock(&x86_cpu_hotplug_driver_mutex);
    }

    void cpu_hotplug_driver_unlock(void)
    {
    - mutex_unlock(&x86_cpu_hotplug_driver_mutex);
    + mutex_unlock(&x86_cpu_hotplug_driver_mutex);
    }

    ssize_t arch_cpu_probe(const char *buf, size_t count) { return -1; }
    ssize_t arch_cpu_release(const char *buf, size_t count) { return -1; }
    -#else
    -static struct task_struct *idle_thread_array[NR_CPUS] __cpuinitdata ;
    -#define get_idle_for_cpu(x) (idle_thread_array[(x)])
    -#define set_idle_for_cpu(x, p) (idle_thread_array[(x)] = (p))
    #endif

    /* Number of siblings per CPU package */
    @@ -618,22 +602,6 @@ wakeup_secondary_cpu_via_init(int phys_a
    return (send_status | accept_status);
    }

    -struct create_idle {
    - struct work_struct work;
    - struct task_struct *idle;
    - struct completion done;
    - int cpu;
    -};
    -
    -static void __cpuinit do_fork_idle(struct work_struct *work)
    -{
    - struct create_idle *c_idle =
    - container_of(work, struct create_idle, work);
    -
    - c_idle->idle = fork_idle(c_idle->cpu);
    - complete(&c_idle->done);
    -}
    -
    /* reduce the number of lines printed when booting a large cpu count system */
    static void __cpuinit announce_cpu(int cpu, int apicid)
    {
    @@ -660,58 +628,31 @@ static void __cpuinit announce_cpu(int c
    * Returns zero if CPU booted OK, else error code from
    * ->wakeup_secondary_cpu.
    */
    -static int __cpuinit do_boot_cpu(int apicid, int cpu)
    +static int __cpuinit do_boot_cpu(int apicid, int cpu, struct task_struct *idle)
    {
    unsigned long boot_error = 0;
    unsigned long start_ip;
    int timeout;
    - struct create_idle c_idle = {
    - .cpu = cpu,
    - .done = COMPLETION_INITIALIZER_ONSTACK(c_idle.done),
    - };
    -
    - INIT_WORK_ONSTACK(&c_idle.work, do_fork_idle);

    alternatives_smp_switch(1);

    - c_idle.idle = get_idle_for_cpu(cpu);
    -
    - /*
    - * We can't use kernel_thread since we must avoid to
    - * reschedule the child.
    - */
    - if (c_idle.idle) {
    - c_idle.idle->thread.sp = (unsigned long) (((struct pt_regs *)
    - (THREAD_SIZE + task_stack_page(c_idle.idle))) - 1);
    - init_idle(c_idle.idle, cpu);
    - goto do_rest;
    - }
    + idle->thread.sp = (unsigned long) (((struct pt_regs *)
    + (THREAD_SIZE + task_stack_page(idle))) - 1);
    + per_cpu(current_task, cpu) = idle;

    - schedule_work(&c_idle.work);
    - wait_for_completion(&c_idle.done);
    -
    - if (IS_ERR(c_idle.idle)) {
    - printk("failed fork for CPU %d\n", cpu);
    - destroy_work_on_stack(&c_idle.work);
    - return PTR_ERR(c_idle.idle);
    - }
    -
    - set_idle_for_cpu(cpu, c_idle.idle);
    -do_rest:
    - per_cpu(current_task, cpu) = c_idle.idle;
    #ifdef CONFIG_X86_32
    /* Stack for startup_32 can be just as for start_secondary onwards */
    irq_ctx_init(cpu);
    #else
    - clear_tsk_thread_flag(c_idle.idle, TIF_FORK);
    + clear_tsk_thread_flag(idle, TIF_FORK);
    initial_gs = per_cpu_offset(cpu);
    per_cpu(kernel_stack, cpu) =
    - (unsigned long)task_stack_page(c_idle.idle) -
    + (unsigned long)task_stack_page(idle) -
    KERNEL_STACK_OFFSET + THREAD_SIZE;
    #endif
    early_gdt_descr.address = (unsigned long)get_cpu_gdt_table(cpu);
    initial_code = (unsigned long)start_secondary;
    - stack_start = c_idle.idle->thread.sp;
    + stack_start = idle->thread.sp;

    /* start_ip had better be page-aligned! */
    start_ip = trampoline_address();
    @@ -813,8 +754,6 @@ do_rest:
    */
    smpboot_restore_warm_reset_vector();
    }
    -
    - destroy_work_on_stack(&c_idle.work);
    return boot_error;
    }

    @@ -851,7 +790,7 @@ int __cpuinit native_cpu_up(unsigned int

    per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;

    - err = do_boot_cpu(apicid, cpu);
    + err = do_boot_cpu(apicid, cpu, tidle);
    if (err) {
    pr_debug("do_boot_cpu failed %d\n", err);
    return -EIO;
    Index: linux-2.6/arch/x86/xen/smp.c
    ===================================================================
    --- linux-2.6.orig/arch/x86/xen/smp.c
    +++ linux-2.6/arch/x86/xen/smp.c
    @@ -250,18 +250,8 @@ static void __init xen_smp_prepare_cpus(
    set_cpu_possible(cpu, false);
    }

    - for_each_possible_cpu (cpu) {
    - struct task_struct *idle;
    -
    - if (cpu == 0)
    - continue;
    -
    - idle = fork_idle(cpu);
    - if (IS_ERR(idle))
    - panic("failed fork for CPU %d", cpu);
    -
    + for_each_possible_cpu(cpu)
    set_cpu_present(cpu, true);
    - }
    }

    static int __cpuinit
    @@ -331,9 +321,8 @@ cpu_initialize_context(unsigned int cpu,
    return 0;
    }

    -static int __cpuinit xen_cpu_up(unsigned int cpu, struct task_struct *tidle)
    +static int __cpuinit xen_cpu_up(unsigned int cpu, struct task_struct *idle)
    {
    - struct task_struct *idle = idle_task(cpu);
    int rc;

    per_cpu(current_task, cpu) = idle;



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