linux-kernel - Re: [RFC] Patch: dynticks: idle load balancing

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Message-ID: <20061213151926.C12795@unix-os.sc.intel.com>
Date:	Wed, 13 Dec 2006 15:19:27 -0800
From:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	nickpiggin@...oo.com.au, vatsa@...ibm.com, clameter@....com,
	tglx@...utronix.de, arjan@...ux.intel.com,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC] Patch: dynticks: idle load balancing

On Thu, Dec 14, 2006 at 12:31:57AM +0100, Ingo Molnar wrote:
> 
> * Siddha, Suresh B <suresh.b.siddha@...el.com> wrote:
> 
> > On Thu, Dec 14, 2006 at 12:13:16AM +0100, Ingo Molnar wrote:
> > > there's another bug as well: in schedule() resched_cpu() is called with 
> > > the current runqueue held in two places, which is deadlock potential. 
> > 
> > resched_cpu() was getting called after prepare_task_switch() which 
> > releases the current runqueue lock. Isn't it?
> 
> no, it doesnt release it. The finish stage is what releases it.

I see.

> the other problem is load_balance(): there this_rq is locked and you 
> call resched_cpu() unconditionally.

But here resched_cpu() was called after double_rq_unlock().

thanks,
suresh
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