Message-ID: <4E1AAF38.9040100@gmail.com>
Date: Mon, 11 Jul 2011 11:07:20 +0300
From: yoni levi <yonicygwin AT gmail DOT com>
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To: cygwin AT cygwin DOT com
Subject: Random fork failures
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Hi,

We have a problem with fork for a very long time.
 From time to time, fork just hangs (with 2 process doing busy loop).
The problem occurs when we do allot of spawns (make system).
It is very easy to recreate the problem, but unfortunately, there is too 
much code involve to send.

I did a little investigation - when the process hangs, I took the 
backtrace with process explorer.
Process explorer does not know anything about cygwin debug symbols, so 
it just give an arbitrary func + offset.
Then I used gdb to find out the real function: sync_proc_pipe doing 
yield in an endless loop.

It seems that there is a race condition here, since this error depends 
on timing. when the CPU is very busy (e.g. when
I do while((1)); do true; done X 4 times), the frequency of the problem 
is reduced.

I dug a little bit in the mailing list and found many references to fork 
failure. I belive this one is similar to my problem - 
http://cygwin.com/ml/cygwin/2011-04/msg00066.html

I also saw all the work done around fork lately 
(http://old.nabble.com/Re%3A-Improvements-to-fork-handling-td31594702.html) 
so I tried to use the latest cygwin from CVS.
This acctualy was very helpful, and this error disappear. the problem is 
that many other errors/crashes are introduced!
Many perl scripts stopped working, rxvt crashes from time to time, gcc 
fails with no good reason and more.

I will appreciate any advice, how can I solve this problem.
Thanks,
Yoni.


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