From owner-freebsd-hackers  Wed Apr  9 14:36:06 1997
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To: Terry Lambert <terry@lambert.org>
cc: ponds!rivers@dg-rtp.dg.com (Thomas David Rivers), hackers@freebsd.org
Subject: Re: Some insight on "dup alloc" problems..... 
In-reply-to: Your message of "Wed, 09 Apr 1997 10:09:09 PDT."
             <199704091709.KAA07150@phaeton.artisoft.com> 
From: David Greenman <dg@root.com>
Reply-To: dg@root.com
Date: Wed, 09 Apr 1997 14:35:09 -0700
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...
>| 		vp = (struct vnode *) malloc((u_long) sizeof *vp,
>| 		    M_VNODE, M_WAITOK);
>                *************************************************

   There are mutex locks in the callers of getnewvnode (specifically UFS)
which force the calls to it to be single-threaded, preventing the vnode
allocation race condition you are refering to. I know because I added them
over a year ago:

revision 1.24
date: 1995/07/21 03:52:40;  author: davidg;  state: Exp;  lines: +34 -4
Implement a lock in ffs_vget to prevent a race condition where two processes
try allocate the same inode/vnode, causing a duplicate.

-DG

David Greenman
Core-team/Principal Architect, The FreeBSD Project