Re: 2.6.25-rc9 -- INFO: possible circular locking dependencydetected

From: Ingo Molnar
Date: Mon Apr 14 2008 - 03:18:39 EST



* Heiko Carstens <heiko.carstens@xxxxxxxxxx> wrote:

> On Mon, Apr 14, 2008 at 08:54:05AM +0200, Peter Zijlstra wrote:
> > Fun,
> >
> > I will need to sort out this code before I can say anything about that,
> > perhaps Gautham and or Rafael have ideas before I can come up with
> > something.. ?
>
> Why not simply removing the get/put_online_cpus() pair in
> sched_getaffinity? It's superfluous since we have already a
> read_lock/read_unlock pair there which does disable/enable cpu hotplug
> anyway.

we dont want to insert such silent "preempt off == hotplug disable"
assumptions - which assumption breaks when the tasklist_lock becomes
preemptible (such as in -rt).

Ingo
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