Re: [PATCH -tip 22/32] sched: Split the cookie and setup per-task cookie on fork

[Peter Zijlstra]

On Tue, Nov 17, 2020 at 06:19:52PM -0500, Joel Fernandes (Google) wrote:

> +/*
> + * Ensure that the task has been requeued. The stopper ensures that the task cannot
> + * be migrated to a different CPU while its core scheduler queue state is being updated.
> + * It also makes sure to requeue a task if it was running actively on another CPU.
> + */
> +static int sched_core_task_join_stopper(void *data)
> +{
> +	struct sched_core_task_write_tag *tag = (struct sched_core_task_write_tag *)data;
> +	int i;
> +
> +	for (i = 0; i < 2; i++)
> +		sched_core_tag_requeue(tag->tasks[i], tag->cookies[i], false /* !group */);
> +
> +	return 0;
> +}
> +
> +static int sched_core_share_tasks(struct task_struct *t1, struct task_struct *t2)
> +{

> +	stop_machine(sched_core_task_join_stopper, (void *)&wr, NULL);

> +}

This is *REALLY* terrible...