Re: [PATCH] sched/kthread: Complain loudly when others violate ourflags

From: Peter Zijlstra
Date: Mon Oct 03 2011 - 06:21:48 EST

On Sun, 2011-10-02 at 18:15 -0700, Tejun Heo wrote:
> Anyways, I don't think I'm gonna take this one. There are some
> attractions to the approach - ie. making the users determine whether
> they need strict affinity or not and mandating those users to shut
> down properly from cpu down callbacks and if we're doing this from the
> scratch, this probably would be a sane choice. But we already have
> tons of users and relatively well tested code. I don't see compelling
> reasons to perturb that at this point.
So wtf am I going to do with people who want PF_THREAD_BOUND to actually
do what it means? Put a warning in the scheduler code to flag all
violations and let you sort out the workqueue fallout?

I didn't write this change for fun, I actually need to get
PF_THREAD_BOUND back to sanity, this change alone isn't enough, but it
gets rid of the worst abuse. This isn't frivolous perturbation.

> Also, on a quick glance, the change is breaking non-reentrance
> guarantee.
How so? Afaict it does exactly what the trustee thread used to do, or is
it is related to the NON_AFFINE moving the worklets around?
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