Re: [Patch] restore the RCU callback to defer put_task_struct() Re:Problems with 2.6.17-rt8

[Esben Nielsen]

On Thu, 10 Aug 2006, Bill Huey wrote:

> On Wed, Aug 09, 2006 at 07:18:35PM -0700, Bill Huey wrote:
> > On Thu, Aug 10, 2006 at 12:05:57AM +0200, Esben Nielsen wrote:
> > > I had a long discussion with Paul McKenney about this. I opposed the patch
> > > from a latency point of view: Suddenly a high-priority RT task could be
> > > made into releasing a task_struct. It would be better for latencies to
> > > defer it to a low priority task.
> > >
> > > The conclusion we ended up with was that it is not a job for the RCU
> > > system, but it ought to be deferred to some other low priority task to
> > > free the task_struct.
> >
> > I agree. It's just hack to get it not to crash at this time. It really
> > should be done in another facility or utilizing another threading context.
>
> Esben and company,
>
> This is the second round of getting rid of the locking problems with free_task()
>
> This extends the mmdrop logic with desched_thread() to also handle free_task()
> requests as well. I believe this address your concerns and I'm open to review
> of this patch.
>
> Patch included:
>
> bill
Without applying the patch and only skimming it it looks like what Paul 
and I concluded :-)

But is there really no generic way of defering this kind of thing? It 
looks like a hell of a lot work where a kind of "message" infrastructure 
could have solved it in a few lines.

Esben
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