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    SubjectRe: cpu hotplug support broken in 2.6.23-rc3
    On Sat, 15 Sep 2007 11:49:41 +0200 Thomas Gleixner <tglx@linutronix.de> wrote:

    > On Fri, 2007-09-14 at 15:15 +0200, Thomas Gleixner wrote:
    > > > Venki sent me an initial patch, but it has issues with the notify
    > > > ordering. Find below my "cache the broadcast flags" version for testing.
    > >
    > > Hmmpf, the flag is still cleared when the cpu goes offline. Need to take
    > > a closer look.
    >
    > I finally tracked it down. There were several ways to turn the box into
    > a brick. Sigh !
    >
    > Can you please test the combo patch below ?
    >
    > The details are available from the for-2.6.23 branch of my hrt git repo:
    >
    > http://git.kernel.org/?p=linux/kernel/git/tglx/linux-2.6-hrt.git;a=shortlog;h=for-2.6.23
    >

    That patch fixes the resume-from-ram and suspend-to-ram regressions on the
    Vaio.

    I dropped the timekeeping.c hunks because they are an older version of
    timekeeping-prevent-time-going-backwards-on-resume.patch which I already
    had.

    Is this good to go? Needs a bit of changelogging.


    drivers/acpi/processor_core.c | 21 +++++++++++++++++++++
    kernel/time/tick-broadcast.c | 24 ++++++++++++++++--------
    kernel/time/tick-sched.c | 12 ++++++++++++
    3 files changed, 49 insertions(+), 8 deletions(-)

    diff -puN drivers/acpi/processor_core.c~cpu-hotplug-support-broken-in-2623-rc3 drivers/acpi/processor_core.c
    --- a/drivers/acpi/processor_core.c~cpu-hotplug-support-broken-in-2623-rc3
    +++ a/drivers/acpi/processor_core.c
    @@ -724,6 +724,25 @@ static void acpi_processor_notify(acpi_h
    return;
    }

    +static int acpi_cpu_soft_notify(struct notifier_block *nfb,
    + unsigned long action, void *hcpu)
    +{
    + unsigned int cpu = (unsigned long)hcpu;
    + struct acpi_processor *pr = processors[cpu];
    +
    + if (action == CPU_ONLINE && pr) {
    + acpi_processor_ppc_has_changed(pr);
    + acpi_processor_cst_has_changed(pr);
    + acpi_processor_tstate_has_changed(pr);
    + }
    + return NOTIFY_OK;
    +}
    +
    +static struct notifier_block acpi_cpu_notifier =
    +{
    + .notifier_call = acpi_cpu_soft_notify,
    +};
    +
    static int acpi_processor_add(struct acpi_device *device)
    {
    struct acpi_processor *pr = NULL;
    @@ -987,6 +1006,7 @@ void acpi_processor_install_hotplug_noti
    ACPI_UINT32_MAX,
    processor_walk_namespace_cb, &action, NULL);
    #endif
    + register_hotcpu_notifier(&acpi_cpu_notifier);
    }

    static
    @@ -999,6 +1019,7 @@ void acpi_processor_uninstall_hotplug_no
    ACPI_UINT32_MAX,
    processor_walk_namespace_cb, &action, NULL);
    #endif
    + unregister_hotcpu_notifier(&acpi_cpu_notifier);
    }

    /*
    diff -puN kernel/time/tick-broadcast.c~cpu-hotplug-support-broken-in-2623-rc3 kernel/time/tick-broadcast.c
    --- a/kernel/time/tick-broadcast.c~cpu-hotplug-support-broken-in-2623-rc3
    +++ a/kernel/time/tick-broadcast.c
    @@ -382,12 +382,23 @@ static int tick_broadcast_set_event(ktim

    int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
    {
    + int cpu = smp_processor_id();
    +
    + /*
    + * If the CPU is marked for broadcast, enforce oneshot
    + * broadcast mode. The jinxed VAIO does not resume otherwise.
    + * No idea why it ends up in a lower C State during resume
    + * without notifying the clock events layer.
    + */
    + if (cpu_isset(cpu, tick_broadcast_mask))
    + cpu_set(cpu, tick_broadcast_oneshot_mask);
    +
    clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);

    if(!cpus_empty(tick_broadcast_oneshot_mask))
    tick_broadcast_set_event(ktime_get(), 1);

    - return cpu_isset(smp_processor_id(), tick_broadcast_oneshot_mask);
    + return cpu_isset(cpu, tick_broadcast_oneshot_mask);
    }

    /*
    @@ -549,20 +560,17 @@ void tick_broadcast_switch_to_oneshot(vo
    */
    void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
    {
    - struct clock_event_device *bc;
    unsigned long flags;
    unsigned int cpu = *cpup;

    spin_lock_irqsave(&tick_broadcast_lock, flags);

    - bc = tick_broadcast_device.evtdev;
    + /*
    + * Clear the broadcast mask flag for the dead cpu, but do not
    + * stop the broadcast device!
    + */
    cpu_clear(cpu, tick_broadcast_oneshot_mask);

    - if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT) {
    - if (bc && cpus_empty(tick_broadcast_oneshot_mask))
    - clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
    - }
    -
    spin_unlock_irqrestore(&tick_broadcast_lock, flags);
    }

    diff -puN kernel/time/tick-sched.c~cpu-hotplug-support-broken-in-2623-rc3 kernel/time/tick-sched.c
    --- a/kernel/time/tick-sched.c~cpu-hotplug-support-broken-in-2623-rc3
    +++ a/kernel/time/tick-sched.c
    @@ -160,6 +160,18 @@ void tick_nohz_stop_sched_tick(void)
    cpu = smp_processor_id();
    ts = &per_cpu(tick_cpu_sched, cpu);

    + /*
    + * If this cpu is offline and it is the one which updates
    + * jiffies, then give up the assignment and let it be taken by
    + * the cpu which runs the tick timer next. If we don't drop
    + * this here the jiffies might be stale and do_timer() never
    + * invoked.
    + */
    + if (unlikely(!cpu_online(cpu))) {
    + if (cpu == tick_do_timer_cpu)
    + tick_do_timer_cpu = -1;
    + }
    +
    if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
    goto end;

    _
    -
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