On 05/16/2014 05:35 PM, Peter Zijlstra wrote:
> On Fri, May 16, 2014 at 11:50:42AM +0800, Lai Jiangshan wrote:
>> After debugging, I found the hotlug-in cpu is atctive but !online in this
>> case.
>> the problem was introduced by 5fbd036b.
>> Some code assumes that any cpu in cpu_active_mask is also online, but
>> 5fbd036b breaks
>> this assumption, so the corresponding code with this assumption should be
>> changed too.
>
> Good find, and yes it does that.
>
>> The following patch is just a workaround. After it is applied, the above
>> WARNING
>> is gone, but I can't hit the wq problem that you found.
>
> Seeing how the entirety of hotplug is basically duct tape and twigs, the
> below isn't that bad.
I think we need to find a more grace solution...
>
>> ---
>> diff --git a/kernel/cpu.c b/kernel/cpu.c
>> index a9e710e..253a129 100644
>> --- a/kernel/cpu.c
>> +++ b/kernel/cpu.c
>> @@ -726,9 +726,10 @@ void set_cpu_present(unsigned int cpu, bool present)
>>
>> void set_cpu_online(unsigned int cpu, bool online)
>> {
>> - if (online)
>> + if (online) {
>> cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
>> - else
>> + cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
>> + } else
>> cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
>> }
>>
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index 268a45e..c1a712d 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -5043,7 +5043,6 @@ static int sched_cpu_active(struct notifier_block *nfb,
>> unsigned long action, void *hcpu)
>> {
>> switch (action & ~CPU_TASKS_FROZEN) {
>> - case CPU_STARTING:
>> case CPU_DOWN_FAILED:
>> set_cpu_active((long)hcpu, true);
>> return NOTIFY_OK;
--
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