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    SubjectRe: [PATCH] clockevent: don't remove broadcast device when cpu is dead
    On Thu, 7 Jan 2010, Xiaotian Feng wrote:

    > Marc reported BUG during shutdown, after debugging, kernel is trying
    > to remove a broadcast device which mode is CLOCK_EVT_MODE_ONESHOT.
    >
    > The root cause for this bug is that in clockevents_notify,
    > "cpumask_weight(dev->cpumask) == 1" is always true even if dev is a

    Why is cpumask_weight(dev->cpumask) == 1 always true when we shutdown
    a non boot cpu ?

    The broadcast device is not a per cpu device and the cpumask should
    not only contain the CPU which is shut down !

    The patch is papering over the real problem.

    Marc, can you please apply the following debug patch and provide the
    dmesg outputs from boot and shutdown ?

    Thanks,

    tglx
    ---

    Index: linux-2.6-tip/kernel/time/clockevents.c
    ===================================================================
    --- linux-2.6-tip.orig/kernel/time/clockevents.c
    +++ linux-2.6-tip/kernel/time/clockevents.c
    @@ -186,7 +186,7 @@ void clockevents_register_device(struct
    BUG_ON(!dev->cpumask);

    raw_spin_lock_irqsave(&clockevents_lock, flags);
    -
    + printk(KERN_ERR "CE register %p %s\n", dev, dev->name);
    list_add(&dev->list, &clockevent_devices);
    clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
    clockevents_notify_released();
    @@ -220,6 +220,7 @@ void clockevents_exchange_device(struct
    * released list and do a notify add later.
    */
    if (old) {
    + printk(KERN_INFO "CE Release %p %s\n", old, old->name);
    clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
    list_del(&old->list);
    list_add(&old->list, &clockevents_released);
    @@ -260,6 +261,13 @@ void clockevents_notify(unsigned long re
    list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
    if (cpumask_test_cpu(cpu, dev->cpumask) &&
    cpumask_weight(dev->cpumask) == 1) {
    + if (dev->mode != CLOCK_EVT_MODE_UNUSED) {
    + printk(KERN_INFO
    + "CE Remove %p %s bc: %d\n",
    + dev, dev->name,
    + tick_is_broadcast_device(dev));
    + continue;
    + }
    BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
    list_del(&dev->list);
    }
    Index: linux-2.6-tip/kernel/time/tick-broadcast.c
    ===================================================================
    --- linux-2.6-tip.orig/kernel/time/tick-broadcast.c
    +++ linux-2.6-tip/kernel/time/tick-broadcast.c
    @@ -72,6 +72,8 @@ int tick_check_broadcast_device(struct c
    (dev->features & CLOCK_EVT_FEAT_C3STOP))
    return 0;

    + printk(KERN_INFO "CE set broadcast %p %s\n", dev, dev->name);
    +
    clockevents_exchange_device(NULL, dev);
    tick_broadcast_device.evtdev = dev;
    if (!cpumask_empty(tick_get_broadcast_mask()))

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