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.
> ---
> 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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