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Date: Wed, 30 Oct 2013 10:48:27 +0100
From: Sebastian Huber <sebastian.huber@embedded-brains.de>
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To: Konstantin Belousov <kostikbel@gmail.com>
Subject: Re: soo_close() vs. filt_soread()
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On 2013-10-29 23:25, Konstantin Belousov wrote:
> On Tue, Oct 29, 2013 at 11:35:04AM +0100, Sebastian Huber wrote:
[...]
 >> Are there some means that prevent this
>> sequence in a real FreeBSD kernel?
>
> When file descriptor gets closed, kevent subsystem is notified first
> and clears knotes related to the filedescriptor (important, not the
> file) being closed. You could see this in the closefp() function calling
> knote_fdclose(). Since files are referenced and destroyed only when the
> last reference vanishes, and filedescriptor holds a reference on the
> file, file (which is socket in your case) cannot go away until knotes
> are expunged.
>
> There are some corner cases, when knotes are really attached to objects
> with different life-cycle, like vnodes, but I believe the description
> above should be accurate enough for sockets.
[...]

Thanks for the hints.  I missed this knote_fdclose() completely.  Similar test 
cases worked for select() and poll() since they use the file descriptor index.

-- 
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
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