linux-kernel - Re: [PATCH 03/19] scheduler: implement workqueue scheduler class

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20091001184824.GA21357@elte.hu>
Date:	Thu, 1 Oct 2009 20:48:24 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Avi Kivity <avi@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Tejun Heo <tj@...nel.org>, jeff@...zik.org,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	jens.axboe@...cle.com, rusty@...tcorp.com.au,
	cl@...ux-foundation.org, dhowells@...hat.com, arjan@...ux.intel.com
Subject: Re: [PATCH 03/19] scheduler: implement workqueue scheduler class


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> On Thu, 1 Oct 2009, Tejun Heo wrote:
> >
> > Implement workqueue scheduler class.  Workqueue sched_class inherits 
> > fair sched_class and behaves exactly the same as sched_class except 
> > that it has two callback functions which get called when a task is 
> > put to sleep and wakes up and doesn't allow switching to different 
> > scheduler class.
> 
> So this looks odd to me.
> 
> I agree completely with the callback functions, but what I don't agree 
> with is that this is somehow workqueue-related. I bet that others 
> could use this, and in fact, I suspect that it should not be tied to 
> the scheduler class at all, but to the _thread_.
> 
> Just as an example, I could imagine that we would do lock_kernel() 
> releasing the kernel lock on scheduling (and re-taking it on wakeup) 
> as a callback. Or async IO handling - both done independently of any 
> "workqueue" logic.
> 
> So tying this to the scheduler class seems a bit odd. But maybe I'm 
> missing something?

We could do what Avi suggested: not use scheduler classes at all for 
this (that brings in other limitations like lack of p->policy freedom), 
but use the existing preempt-notifications callbacks.

They are per task - we would simply make preempt notifiers 
unconditional, i.e. remove CONFIG_PREEMPT_NOTIFIERS and make it all 
unconditional scheduler logic.

( Sidenote: we could even unify that logic with the perf event 
  sched-in/sched-out logic which is per task in a similar fashion and 
  which can have callback properties as well. That would mean a single,
  well-defined callback facility for scheduler events. )

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/