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Date: Thu, 26 Oct 2000 18:46:49 -0700
From: Alfred Perlstein <bright@wintelcom.net>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Jonathan Lemon <jlemon@flugsvamp.com>, Gideon Glass <gid@cisco.com>,
        Simon Kirby <sim@stormix.com>, Dan Kegel <dank@alumni.caltech.edu>,
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Subject: Re: kqueue microbenchmark results
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* Alan Cox <alan@lxorguk.ukuu.org.uk> [001026 18:33] wrote:
> > the application of a close event.  What can I say, "the fd formerly known
> > as X" is now gone?  It would be incorrect to say that "fd X was closed",
> > since X no longer refers to anything, and the application may have reused
> > that fd for another file.
> 
> Which is precisely why you need to know where in the chain of events this
> happened. Otherwise if I see
> 
> 	'read on fd 5'
> 	'read on fd 5'
> 
> How do I know which read is for which fd in the multithreaded case

No you don't, you don't see anything with the current code unless
fd 5 is still around, what you're presenting to Jonathan is a
application threading problem, not something that need to be
resolved by the OS.

> > As for the multi-thread case, this would be a bug; if one thread closes
> > the descriptor, the other thread is going to get an EBADF when it goes 
> > to perform the read.
> 
> Another thread may already have reused the fd

This is another example of an application threading problem.

-- 
-Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org]
"I have the heart of a child; I keep it in a jar on my desk."
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