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From: "Williams, David" <dwilliams AT solekai DOT com>
To: "cygwin AT cygwin DOT com" <cygwin AT cygwin DOT com>
Date: Wed, 30 Apr 2008 16:10:41 -0700
Subject: RE: Problem with cygserver and sysv message queues: msgsnd()  	blocks  forever.
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Corinna,

I can report that the patch works perfectly. Both with the examples
and with our original application program that brought the bug to
our attention.

Dave Williams

-----Original Message-----
From: cygwin-owner AT cygwin DOT com [mailto:cygwin-owner AT cygwin DOT com] On Behalf Of Corinna Vinschen
Sent: Wednesday, April 30, 2008 11:58 AM
To: cygwin AT cygwin DOT com
Subject: Re: Problem with cygserver and sysv message queues: msgsnd() blocks forever.

On Apr 30 10:16, Williams, David wrote:
> Yes, I can patch and build the sources, and will test the patch. I
> can see that this will work, and is probably the least disruptive
> way to fix it. I'm bothered a little bit by the fixed timeout value,
> although this is an exceptional case, which shouldn't occur in a
> properly tuned and managed system.

I'm not that concerned.  A fixed value of 50 will interrupt a maximum of
20 times per second.  The hz value in BSD is usually higher.  I think 50
is a good compromise.

> My thoughts for a fix were centered around replacing the msqptr
> ident parameter with a resource specific identifier that would
> allow freeing a resource by one queue to wake another. However,
> such a fix would require much regression testing, and STILL might
> need a timeout like this as an ultimate safety net. Besides, we
> likely want to continue tracking the BSD source.

There's surely some better way to solve this problem but if there's
an upstream fix, I'd like to use it.  My goal is to keep the code as
much upstream centered as possible.

> I'm currently building and testing using the cygwin-1.5.25-12 release
> tarball. Would it be more helpful for me to pull the CVS head down
> to test this?

Shouldn't matter, actually.  There's no difference in the message queue
code between 1.5.25 and CVS HEAD.  However, the bugfix will only go into
CVS HEAD.  If you need this bugfix desperately, please maintain your
local version for now.

> Thanks for the quick reply. I'm glad to be of some help.

You're welcome.  Thanks for the debugging effort and the testcase.
You almost did all the work yourself already, I just had to look
what upstream is doing about it :)

I'll check this in in a couple of minutes.


Thanks again,
Corinna

--
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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