linux-kernel - Re: [PATCH] sched/kthread: Complain loudly when others violate our flags

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Message-ID: <1317637238.20367.6.camel@twins>
Date:	Mon, 03 Oct 2011 12:20:38 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Tejun Heo <htejun@...il.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] sched/kthread: Complain loudly when others violate our
 flags

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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