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Date:      Wed, 24 Jan 2001 23:10:51 +1100 (EST)
From:      Bruce Evans <bde@zeta.org.au>
To:        Alfred Perlstein <bright@wintelcom.net>
Cc:        John Baldwin <jhb@FreeBSD.org>, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject:   Re: cvs commit: src/sys/isofs/cd9660 cd9660_vfsops.c
Message-ID:  <Pine.BSF.4.21.0101242229170.44683-100000@besplex.bde.org>
In-Reply-To: <20010123163418.N26076@fw.wintelcom.net>

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On Tue, 23 Jan 2001, Alfred Perlstein wrote:

> * John Baldwin <jhb@FreeBSD.org> [010123 16:26] wrote:
> > jhb         2001/01/23 16:26:19 PST
> > 
> >   Modified files:
> >     sys/isofs/cd9660     cd9660_vfsops.c 
> >   Log:
> >   Proc locking to protect p_ucred while we obtain additional references.
> 
> I really don't think you need the PROC_LOCK for these.
> 
> You only need the 'uc' variable, and even then it's only to protect
> against rfork threads playing with setuid which is an inhernent
> race condition as p_ucred shouldn't be NULL.  (afaik).

I don't think you need any locking or crhold()ing for these.  I think
xxx_mount() is only called with p == curproc, so p_ucred can't change.
Unfortunately, most vfs and vnop interfaces including VFS_MOUNT() make
it unclear that p == curproc by pretending to support arbitrary p's.

> Just give it some more thought, because I'm not sure I'm right
> about this.

Me too.

Bruce



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