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From: "Arash Partow" <arashp AT hotmail DOT com>
To: cygwin AT cygwin DOT com
Subject: Serious problem with win32 pthreads crashing and c++ class
Date: Tue, 21 Oct 2003 08:09:47 +0000
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Message-ID: <BAY9-F22zQSWds7vWeU0003aa4b@hotmail.com>

Hi All,

I'm a long-time reader, first-time poster. I've been doing some work lately
with posix threads, mainly trying to build a very simple c++ wrapper for
Posix threads, and well have come up to a stumbling point on the win32
platform with a simple prototype i had built utilizing this c++ wrapper.

On the Linux and BSD(free and open) platforms the simple prototype works
perfectly, it does not crash and does not seem to produce any zombie
processes. In one instance I've had it running for 3 days none stop(on RH-
Linux 9.0) and during this time it had created and execute over 16 million
threads.

The prototype initially creates 700 threads all of which are contained in a
vector (threadList), each thread does some "simple" string processing
(basically tokenize a string) and then exists. On completion of the thread,
the thread sets its own state in the thread-class to dead.

Another thread called GarbageCollector, which is created before the other
threads are created, is continually traversing the threadList, looking for
dead threads, once a dead thread is found, it deletes the pointer pointing
to the thread class in the list, creates a new thread and adds it to the
end of the list. Hence continually maintaining the number of threads being
run at any one time, (hopefully)

The problem is on Windows2000 and WindowsXP (with SP4) the prototype only
ever gets to about 50000 threads or so, never getting past that amount, it
always crashes. several times I've tried using GDB to figure out where its
crashing however its always seems to be crashing in different place. I've
made sure i don't use any methods from the standard libs that use globals,
and tried implementing a reentrant way of development.

I've tried reducing the number of overall threads (MAX_THREADS), down to
100, 50, 10, it still crashes its just takes longer to crash.

I've tried turning optimization on and off for GCC, nothing changes. except
for a slightly longer compile time which is due to something else. What
really baffles me is that it works well under unix platforms but falls over
on win32.


My questions are:

1.) could you please look at the code from this URL 
http://www.partow.net/downloads/thread-question.zip
    and tell me if any of you can replicate what i am seeing.

2.) if there is a problem, is the problem from my code or is it from the
    implementation of win32 pthreads, or is it a windows issue?

3.) is the general way the Thread class been written correct, or is there a
    better way to do it?

4.) Is there a better way to implement a Thread class?


My setup is as follows:

1.) GCC version 3.3.1 (cygming special)
2.) P4 2.4, 1024GB DDR
3.) Windows 2000


My intention is to hopefully extent the class base and combine it with some
sort of sockets class the implement a per-thread-per-connection based
client/server system for doing something interesting. I'm not looking for
windows based implementations cause I'm trying to keep the code as portable
as possible.

Any help regarding this matter would be very much appreciated.


Regards


Arash


PS: To make and run the source code, you gotta have GCC installed 2.95 or
    later plus win32-pthreads installed. Other than that type:
    make ThreadTest
    ThreadTest


__________________________________________________
Be one who knows what they don't know,
Instead of being one who knows not what they don't know,
Thinking they know everything about all things.
http://www.partow.net

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