Date: Sun, 10 Jun 2007 16:16:16 +0100
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Eric Dumazet <dada1@cosmosbay.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
       Al Viro <viro@ftp.linux.org.uk>, Kyle Moffett <mrmacman_g4@mac.com>,
       Ulrich Drepper <drepper@redhat.com>,
       Davide Libenzi <davidel@xmailserver.org>, Theodore Tso <tytso@mit.edu>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>, Ingo Molnar <mingo@elte.hu>
Subject: Re: [patch 7/8] fdmap v2 - implement sys_socket2
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> > and there's absolutely nothing wrong with this kind of setup, even if you 
> > could obviously have done it other ways too (ie by using "dup2()" instead 
> > of "close + open"),
> > 
> 
> This kind of setup was OK 25 years ago, before multithreading era.
> You cannot reasonably expect it to work in a multithreaded program.

Why not.

When execution begins which is the normal point you do this then you've
got one thread. If you need to do this from a thread after that point
posix provides threaded applications with locking.

Not much else works in a threaded app if you get the locking wrong, and
that is considered the authors job. Why is fd allocation different ?
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