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Re: [RFC] 12658_thread.cc randomly fails (on MP machines)


Paolo Carlini wrote:

Point 2- is much more nasty, because implies that *any* locale can be in fact a ref-copy of _S_global or _S_classic! In principle, *every* operation on locales (e.g., also the copy constructor, the assignment operator) can be dangerous and must be protected.
Therefore, it looks like we have to make a decision: either we add locking bits in a few other places (much better if we can do that with zero overhead in the non-multithreaded case), or we can stay with something simpler.

Well, I think that the above is by and large incorrect: the other operations (besides locale::global() and locale::locale(), I mean) do *not* access _S_global directly and therefore seem safe. My bad, sorry.


Therefore, the problem must be somewhere else...

Now, I'm tentatively suspecting everything related to the locale::locale(const char*) constructor. If I change the original testcase as in the attached to avoid that specific constructor but otherwise keeping its full complexity, it doesn't fail anymore on 4-way machines.

Paolo.

/////////////
// { dg-do run { target *-*-freebsd* *-*-netbsd* *-*-linux* *-*-solaris* *-*-cygwin *-*-darwin* alpha*-*-osf* } }
// { dg-options "-pthread" { target *-*-freebsd* *-*-netbsd* *-*-linux* alpha*-*-osf* } }
// { dg-options "-pthreads" { target *-*-solaris* } }

// Copyright (C) 2004 Free Software Foundation
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.

// 22.1.1.2 locale constructors and destructors [lib.locale.cons]

#include <locale>
#include <pthread.h>
 
const int max_thread_count = 20;
//const int max_loop_count = 1000000; // orig value
const int max_loop_count = 100000;
const int max_locales = 10;
std::locale loc_en = std::locale("en_US");
std::locale loc_fr = std::locale("fr_FR");

void* thread_main(void*)
{
  try
    {
      std::locale loc_c = std::locale::classic();
      std::locale loc[max_locales];
      for (int j = 0; j < max_locales; ++j)
	loc[j] = std::locale(j % 2 ? loc_en : loc_fr);
      
      for (int i = 0; i < max_loop_count; ++i)
	{
	  int k = i % max_locales;
	  loc[k] = std::locale::global(loc[k]);
	  
	  if (i % 37 == 0)
	    loc[k] = loc[k].combine<std::ctype<char> >(loc_c);
	}
    }
  catch (...) { }
  return 0;
}
 
int
main()
{
  pthread_t tid[max_thread_count];
  
  for (int i = 0; i < max_thread_count; i++)
    pthread_create (&tid[i], NULL, thread_main, 0);
  
  for (int i = 0; i < max_thread_count; i++)
    pthread_join (tid[i], NULL);

  return 0;
}

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