Re: [PATCH] fs/dcache: resched/chill only if we make no progress

[Thomas Gleixner]

On Thu, 8 Sep 2016, Sebastian Andrzej Siewior wrote:
> +		if (parent == dentry) {
> +			/* the task with the highest priority won't schedule */
> +			r = cond_resched();
> +			if (!r && (rt_task(current) || dl_task(current)))

That's wrong because a non RT task will just spin until its time slice is
up. Wasted cycles for nothing.

Ideally we make spinning conditional on 

    !on_cpu(dentry->lock->owner)

That would avoid going to sleep if the owner runs on another cpu. We have
no mechanism for that, but I think it'd be worth to think about one.

> +				cpu_chill();
> +		} else
> +			dentry = parent;

Missing braces

Thanks,

	tglx