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Date: Thu, 11 Jan 2007 16:44:51 +0100
From: "Attilio Rao" <attilio@freebsd.org>
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To: "John Baldwin" <jhb@freebsd.org>
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References: <20070107171034.GA13836@crodrigues.org>
	<20070110142100.G52843@fledge.watson.org> <45A5004B.6090402@cisco.com>
	<200701101431.57695.jhb@freebsd.org>
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Cc: Craig Rodrigues <rodrigc@crodrigues.org>, Randall Stewart <rrs@cisco.com>,
	freebsd-current@freebsd.org, Robert Watson <rwatson@freebsd.org>
Subject: Re: Witness warning with SCTP
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2007/1/10, John Baldwin <jhb@freebsd.org>:
> On Wednesday 10 January 2007 10:03, Randall Stewart wrote:
> > Robert/All:
> >
> > Ok, here is the deal... I have looked in a bit
> > closer at this..
> >
> > Here is what is happening...
> >
> > When a cookie arrives, we get a "create lock" on
> > the socket this prevents the user on the same
> > socket from creating a assoc at the same exact time.
>
> Can't you do a model like this:
>
>        lock();
>        if (need to create pcb) {
>                unlock();
>                create_pcb();  // can sleep w/o holding lock
>                lock();
>                if (someone else created the pcb)
>                        free(pcb_I_just_created);
>        }
>        unlock();

But it is quite impossible to get rid of M_WAITOK in this case (IIUC,
this should be the sleeping point)?

Attilio


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