linux-kernel - Re: [RFC PATCH 1/4] Refcount Based Cpu-Hotplug Implementation

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Message-Id: <200710171629.13060.rusty@rustcorp.com.au>
Date:	Wed, 17 Oct 2007 16:29:12 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	ego@...ibm.com
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Oleg Nesterov <oleg@...sign.ru>, Ingo Molnar <mingo@...e.hu>,
	Paul E McKenney <paulmck@...ibm.com>
Subject: Re: [RFC PATCH 1/4] Refcount Based Cpu-Hotplug Implementation

On Wednesday 17 October 2007 15:37:54 Gautham R Shenoy wrote:
> On Wed, Oct 17, 2007 at 10:47:41AM +1000, Rusty Russell wrote:
> > On Tuesday 16 October 2007 20:34:17 Gautham R Shenoy wrote:
> > > This patch implements a Refcount + Waitqueue based model for
> > > cpu-hotplug.
> >
> > Hi Gautham,
>
> Hi Rusty,
>
> > 	I can't see where you re-initialize the completion.
>
> The cpu_hotplug.readers_done is a global variable which has been
> initialized in cpu_hotplug_init.
>
> So I am wondering is the re-initialization required ?

Yes.  AFAICT you use this completion on every hotplug.  Yet once a completion 
is completed, it needs to be re-initialized to be reused: it's "complete" and 
wait_for_completion will return immediately thereafter.

Perhaps you want a waitqueue instead?

Rusty.
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