[ROOT] Starting TThreads

From: Volker Hejny (V.Hejny@fz-juelich.de)
Date: Wed Jun 11 2003 - 10:43:17 MEST


Dear all,

in some recent ROOT version I observed, that some debug output using
TThread::Printf(...) in TThread::Fun() is now surrounded by an
if (gDebug) { ... } statement. This reminds me of some old question
of mine, which I want to repeat now.

Our original problem was, that after a TThread::Run() the correspoding
thread kept hanging in the first TThread::Printf() call in the
function TThread::Fun(). Only when commenting out these Printf() calls
we got our programs run - without any further problems with TThread
during the last 1 1/2 years. However, we always had to comment out
these lines in TThread::Fun().

Consider the following small program:

#include "TThread.h"
#include <iostream>

void* handle(void* ptr) {
  int nr = (int) ptr;

  while (1) {
    TThread::Lock();
    std::cerr << "Here I am: " << nr << std::endl;
    TThread::UnLock();
    sleep(1);
  }
}

int main() {
  // gDebug = 1;

  std::cerr << "Starting Thread 1" << std::endl;
  TThread *h1 = new TThread("h1", handle, (void*) 1);
  h1->Run();
  std::cerr << "Starting Thread 2" << std::endl;
  TThread *h2 = new TThread("h2", handle, (void*) 2);
  h2->Run();
  std::cerr << "Starting Thread 3" << std::endl;
  TThread *h3 = new TThread("h3", handle, (void*) 3);
  h3->Run();
  while(1) {}
}

In this configuration (with the actual cvs version of ROOT) everything
runs fine on all machines (various Linux distributions). But if one 
enables 'gDebug = 1' the main program reaches the while-loop, but
the threads are not running but sticking in the TThread::Fun() function.

Since nobody else was complaining about such a behaviour, I assume
that the this does not occur for other people. Any clue?

Best regards,
Volker

-- 
Dr. Volker Hejny                Tel: 02461/616853                      ** 
Institut f. Kernphysik          Fax: 02461/613930                     **
---------------------------------------------------------------- **  ** ---  
Forschungszentrum Juelich GmbH, D-52425 Juelich                    **



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