Re: [PATCH 4/7] sched: implement force_cpus_allowed()

[Peter Zijlstra]

On Tue, 2009-12-08 at 11:34 +0100, Peter Zijlstra wrote:
> On Tue, 2009-12-08 at 18:12 +0900, Tejun Heo wrote:
> > > So its only needed in order to flush a workqueue from CPU_DOWN_PREPARE?
> > > And all you need it to place a new kthread on a !active cpu?
> > 
> > Yes, that's all I need. 
> 
> Then you don't need most of that patch, you don't need to touch the
> migration stuff since a new kthread isn't running.
> 
> All you need to do is make a kthread_bind/set_cpus_allowed variant that
> checks against cpu_online_mask instead of cpu_active_mask.
> 
> It might even make sense to have kthread_bind() always check with
> cpu_online_mask as the kernel really ought to know what its doing
> anyway.
> 
> You also don't need to play trickery with PF_THREAD_BOUND, since a new
> kthread will not have that set.
> 
> In fact, your patch is against a tree that still has cpu_online_mask in
> all those places, so you wouldn't have needed any of that, confused.. ?!

More confusion, kthread_bind() doesn't even use set_cpus_allowed() so it
wouldn't have hit any of that crap.

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