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    Subject[patch 1/6] x86: simplify idle selection
    default_idle is selected in cpu_idle(), when no other idle routine is
    selected. Select it in select_idle_routine() when mwait is not
    selected.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: Andreas Herrmann <andreas.herrmann3@amd.com>

    ---
    arch/x86/kernel/process.c | 18 +++++++-----------
    arch/x86/kernel/process_32.c | 7 +------
    arch/x86/kernel/process_64.c | 7 ++-----
    3 files changed, 10 insertions(+), 22 deletions(-)

    Index: linux-2.6/arch/x86/kernel/process.c
    ===================================================================
    --- linux-2.6.orig/arch/x86/kernel/process.c
    +++ linux-2.6/arch/x86/kernel/process.c
    @@ -139,27 +139,23 @@ static int __cpuinit mwait_usable(const

    void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
    {
    - static int selected;
    -
    - if (selected)
    - return;
    #ifdef CONFIG_X86_SMP
    if (pm_idle == poll_idle && smp_num_siblings > 1) {
    printk(KERN_WARNING "WARNING: polling idle and HT enabled,"
    " performance may degrade.\n");
    }
    #endif
    + if (pm_idle)
    + return;
    +
    if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) {
    /*
    - * Skip, if setup has overridden idle.
    * One CPU supports mwait => All CPUs supports mwait
    */
    - if (!pm_idle) {
    - printk(KERN_INFO "using mwait in idle threads.\n");
    - pm_idle = mwait_idle;
    - }
    - }
    - selected = 1;
    + printk(KERN_INFO "using mwait in idle threads.\n");
    + pm_idle = mwait_idle;
    + } else
    + pm_idle = default_idle;
    }

    static int __init idle_setup(char *str)
    Index: linux-2.6/arch/x86/kernel/process_32.c
    ===================================================================
    --- linux-2.6.orig/arch/x86/kernel/process_32.c
    +++ linux-2.6/arch/x86/kernel/process_32.c
    @@ -168,24 +168,19 @@ void cpu_idle(void)
    while (1) {
    tick_nohz_stop_sched_tick();
    while (!need_resched()) {
    - void (*idle)(void);

    check_pgt_cache();
    rmb();
    - idle = pm_idle;

    if (rcu_pending(cpu))
    rcu_check_callbacks(cpu, 0);

    - if (!idle)
    - idle = default_idle;
    -
    if (cpu_is_offline(cpu))
    play_dead();

    local_irq_disable();
    __get_cpu_var(irq_stat).idle_timestamp = jiffies;
    - idle();
    + pm_idle();
    }
    tick_nohz_restart_sched_tick();
    preempt_enable_no_resched();
    Index: linux-2.6/arch/x86/kernel/process_64.c
    ===================================================================
    --- linux-2.6.orig/arch/x86/kernel/process_64.c
    +++ linux-2.6/arch/x86/kernel/process_64.c
    @@ -150,12 +150,9 @@ void cpu_idle(void)
    while (1) {
    tick_nohz_stop_sched_tick();
    while (!need_resched()) {
    - void (*idle)(void);

    rmb();
    - idle = pm_idle;
    - if (!idle)
    - idle = default_idle;
    +
    if (cpu_is_offline(smp_processor_id()))
    play_dead();
    /*
    @@ -165,7 +162,7 @@ void cpu_idle(void)
    */
    local_irq_disable();
    enter_idle();
    - idle();
    + pm_idle();
    /* In many cases the interrupt that ended idle
    has already called exit_idle. But some idle
    loops can be woken up without interrupt. */
    --



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