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    Subject[patch 3/9] cpu: deliver CPU_UP_CANCELED only to NOTIFY_OKed callbacks with CPU_UP_PREPARE
    From: Akinobu Mita <>

    The functions in a CPU notifier chain is called with CPU_UP_PREPARE event
    before making the CPU online. If one of the callback returns NOTIFY_BAD,
    it stops to deliver CPU_UP_PREPARE event, and CPU online operation is canceled.
    Then CPU_UP_CANCELED event is delivered to the functions in a CPU notifier
    chain again.

    This CPU_UP_CANCELED event is delivered to the functions which have been
    called with CPU_UP_PREPARE, not delivered to the functions which haven't
    been called with CPU_UP_PREPARE.

    The problem that makes existing cpu hotplug error handlings complex is
    that the CPU_UP_CANCELED event is delivered to the function that has
    returned NOTIFY_BAD, too.

    Usually we don't expect to call destructor function against the
    object that has failed to initialize. It is like:

    err = register_something();
    if (err) {
    return err;

    So it is natural to deliver CPU_UP_CANCELED event only to the functions
    that have returned NOTIFY_OK with CPU_UP_PREPARE event and not to call
    the function that have returned NOTIFY_BAD. This is what this patch is doing.

    Otherwise, every cpu hotplug notifiler has to track whether
    notifiler event is failed or not for each cpu.
    (drivers/base/topology.c is doing this with topology_dev_map)

    Similary this patch makes same thing with CPU_DOWN_PREPARE and
    CPU_DOWN_FAILED evnets.

    Cc: Rusty Russell <>
    Signed-off-by: Akinobu Mita <>

    kernel/cpu.c | 2 ++
    1 file changed, 2 insertions(+)

    Index: 2.6-git/kernel/cpu.c
    --- 2.6-git.orig/kernel/cpu.c
    +++ 2.6-git/kernel/cpu.c
    @@ -150,6 +150,7 @@ static int _cpu_down(unsigned int cpu, i
    err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
    hcpu, -1, &nr_calls);
    if (err == NOTIFY_BAD) {
    + nr_calls--;
    __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
    hcpu, nr_calls, NULL);
    printk("%s: attempt to take down CPU %u failed\n",
    @@ -233,6 +234,7 @@ static int __cpuinit _cpu_up(unsigned in
    ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE | mod, hcpu,
    -1, &nr_calls);
    if (ret == NOTIFY_BAD) {
    + nr_calls--;
    printk("%s: attempt to bring up CPU %u failed\n",
    __FUNCTION__, cpu);
    ret = -EINVAL;
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      Last update: 2007-07-22 17:49    [W:0.023 / U:0.384 seconds]
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