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SubjectRe: [PATCH 2/4] context_tracking: Inherit TIF_NOHZ through forks instead of context switches
On Tue, Apr 21, 2015 at 02:23:07PM +0200, Frederic Weisbecker wrote:
> +void __init context_tracking_cpu_set(int cpu)
> {
> + static __initdata bool initialized = false;
> + struct task_struct *p, *t;
> +
> + if (!per_cpu(context_tracking.active, cpu)) {
> + per_cpu(context_tracking.active, cpu) = true;
> + static_key_slow_inc(&context_tracking_enabled);
> + }
> +
> + if (initialized)
> + return;
> +
> + set_tsk_thread_flag(&init_task, TIF_NOHZ);
> +
> + /*
> + * There shouldn't be any thread at this early boot stage
> + * but the scheduler is ready to host any. So lets walk
> + * the tasklist just in case. tasklist_lock isn't necessary
> + * either that early but take it for correctness checkers.
> + */
> + read_lock(&tasklist_lock);
> + for_each_process_thread(p, t)
> + set_tsk_thread_flag(t, TIF_NOHZ);

If there should not be any task, should there not be a WARN_ON_ONCE()
here?

> + read_unlock(&tasklist_lock);
> +
> + initialized = true;
> }


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