PERFORCE change 14877 for review

[Robert Watson]

On Wed, 24 Jul 2002, Bosko Milekic wrote:

> On Wed, Jul 24, 2002 at 07:21:38PM -0700, Robert Watson wrote:
> > http://people.freebsd.org/~peter/p4db/chv.cgi?CH=14877
> > 
> > Change 14877 by rwatson at rwatson_curry on 2002/07/24 19:21:02
> > 
> > 	Hopefully a bug fix for a bug whereby when one pipe end is
> > 	terminated, the label is prematurely destroyed, resulting in
> > 	a blank label during follow-up policy checks.  I believe this
> > 	change modifies the logic so that the pipe label is destroyed
> > 	only when the second end-point is removed.  We'll see if this
> > 	corrects the problem I'm bumping into.
> 
>    Since you have one mutex and one label for both ends of the
>    bi-directional pipe, why don't you just use the code already in place
>    for destroying the mutex 'safely' to also destroy the label?  In
>    other words, pipeclose() has this `hadpeer' variable which it
>    increments if it finds that the other end exists (and the mutex is
>    grabbed, then).  In other words, just group the label destroy with
>    the mutex destroy.  If one is wrong, they're both wrong and you can
>    fix them both at the same time.  I think that you should only be
>    destroying the label if it hasn't already been initialized, as well.
>    It could be that this is a partially created pipe and so the mutex
>    (and possibly the label?) have not yet been created.  I would examine
>    this further myself but it'll have to wait... :-(

Yeah, I think there may be windows where for fdesc-shared processes (and
presumably KSE's), the pipe is present but not yet available.  An
interesting question is whether you can perform pipe operations in the
window, and if so, whether we need to initialize the labels earlier, and
destroy them later.

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert at fledge.watson.org      Network Associates Laboratories


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