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

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Date:	Thu, 14 Dec 2006 00:31:57 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
Cc:	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


* 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.

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

	Ingo
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