Subject: Re: PATCH: Fix race in cpu_down (hotplug cpu)
From: Nigel Cunningham <ncunningham@cyclades.com>
Reply-To: ncunningham@cyclades.com
To: vatsa@in.ibm.com
Cc: Li Shaohua <shaohua.li@intel.com>, Andrew Morton <akpm@osdl.org>,
       Linus Torvalds <torvalds@osdl.org>,
       Zwane Mwaikambo <zwane@arm.linux.org.uk>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Rusty Russell <rusty@rustcorp.com.au>
In-Reply-To: <20050919052830.GB8653@in.ibm.com>
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Organization: Cyclades
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Date: Mon, 19 Sep 2005 15:35:22 +1000
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On Mon, 2005-09-19 at 15:28, Srivatsa Vaddagiri wrote:
> On Mon, Sep 19, 2005 at 03:23:01PM +1000, Nigel Cunningham wrote:
> > Maybe I'm just an ignoramus, but I was thinking (without being a
> > scheduler expert at all) that if the idle thread was already running,
> > trying to set it up to run next might possibly have zero effect. I've
> 
> sched_idle_next actually adds the idle task to its runqueue (normally
> it is not present in a runqueue while running) and as well changes its 
> priority/policy. So it does have *some* effect!

Ok.

> > added a bit of debugging code to try and see in better detail what's
> > happening.
> 
> Could you elaborate (with some stack traces maybe) on the deadlock you are 
> seeing during resume? Maybe that can throw some light.

I'll try. I'm having trouble reproducing it now (yes, having reversed my
patch!).

Regards,

Nigel
-- 


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