Re: [BUG] long freezes on thinkpad t60

[Ingo Molnar]

* Miklos Szeredi <miklos@xxxxxxxxxx> wrote:

> > could you try the quick hack below, ontop of cfs-v17? It adds two 
> > things to wait_task_inactive():
> > 
> > - a cond_resched() [in case you are running !PREEMPT]
> > 
> > - use MONITOR+MWAIT to monitor memory transactions to the rq->curr
> >   cacheline. This should make the polling loop definitely fair.
> 
> Is it not possible for the mwait to get stuck?

it is - when the other CPU does nothing.

> > If this solves the problem on your box then i'll do a proper fix and 
> > introduce a cpu_relax_memory_change(*addr) type of API to around 
> > monitor/mwait. This patch boots fine on my T60 - but i never saw 
> > your problem.
> 
> Yes, the patch does make the pauses go away.  In fact just the 
> smp_mb() seems to suffice.

cool! Could you send me the smallest patch you tried that still made the 
hangs go away?

	Ingo
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