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Date: Mon, 4 Oct 2004 11:38:54 -0400
From: David Schultz <das@FreeBSD.ORG>
To: John Baldwin <jhb@FreeBSD.ORG>
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Subject: Re: cvs commit: src/sys/kern kern_fork.c
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On Mon, Oct 04, 2004, John Baldwin wrote:
> On Friday 01 October 2004 01:01 am, David Schultz wrote:
> > das         2004-10-01 05:01:29 UTC
> >
> >   FreeBSD src repository
> >
> >   Modified files:
> >     sys/kern             kern_fork.c
> >   Log:
> >   Avoid calling _PHOLD(p1) with p2's lock held, since _PHOLD()
> >   may block to swap in p1.  Instead, call _PHOLD earlier, at a
> >   point where the only lock held happens to be p1's.
> 
> FWIW, I don't think this can actually happen because curthread belonging to p1 
> is executing and it wouldn't be executing unless it was swapped in, so I 
> don't think that PHOLD could ever have blocked.

Yes, you're right.  I'll revert this one.  Shall I also change the
_PHOLD() into simply p1->p_lock++ (and similarly for _PRELE()) to
avoid the useless test?