default_weaktoshared timeouts

[Jack Howarth]

On Fri, Apr 02, 2010 at 06:10:29PM +0100, Jonathan Wakely wrote:
> On 2 April 2010 14:12, Jack Howarth wrote:
> >
> > Paolo,
> >   I don't believe this occurs with the x86_64-apple-darwin10
> > target but only with i686-apple-darwin10 so it may well be
> > a bug in the 32-bit linker on darwin. I'll try benchmarking the
> > actual linkage command at both 32-bit and 64-bit to see if
> > it can be reproduced. If so, I'll file a radar bug report.
> 
> It's running the test that is timing out rather than the linker
> command.  It would be helpful to know if the test is actually stuck,
> or just running so slowly it times out and gets killed.
> 
> Can you reproduce it just by building the attached file with
> -std=gnu++0x and running it in a loop?  This is just a standalone copy
> of the testsuite that doesn't need the testsuite_hooks.h header.  If
> it is getting stuck please CC me on a bug report.
> 
> Thanks,
> 
> Jonathan

> // Copyright (C) 2006, 2007, 2008, 2009 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 3, 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 COPYING3.  If not see
> // <http://www.gnu.org/licenses/>.
> 
> // 20.6.6.2 Template class shared_ptr [util.smartptr.shared]
> 
> // { dg-do run { target *-*-freebsd* *-*-netbsd* *-*-linux* *-*-solaris* *-*-cygwin *-*-darwin* alpha*-*-osf* mips-sgi-irix6* } }
> // { dg-options "-pthread -std=gnu++0x" { target *-*-freebsd* *-*-netbsd* *-*-linux* alpha*-*-osf* mips-sgi-irix6* } }
> // { dg-options "-pthreads -std=gnu++0x" { target *-*-solaris* } }
> // { dg-options " -std=gnu++0x " { target *-*-cygwin *-*-darwin* } }
> 
> #include <memory>
> #include <random>
> #include <vector>
> #include <assert.h>
> #define VERIFY assert
> #include <iostream>
> #include <cstdlib>
> 
> #include <pthread.h>
> 
> #ifdef _GLIBCXX_HAVE_UNISTD_H
> #include <unistd.h>	// To test for _POSIX_THREAD_PRIORITY_SCHEDULING
> #endif
> 
> /* This (brute-force) tests the atomicity and thus thread safety of the
>  * shared_ptr <- weak_ptr
>  * assignment operation by allocating a test object, retrieving a weak
>  * reference to it, and letting a number of threads repeatedly create strong
>  * references from the weak reference.
>  * Specifically, this tests the function _Sp_counted_base<true>::add_ref_lock()
>  */
> 
> 
> const unsigned int HAMMER_MAX_THREADS = 10;
> const unsigned int POOL_SIZE = 1000;
> const unsigned long HAMMER_REPEAT = 100000;
> const unsigned long KILL_ONE_IN = 1000;
> 
> struct A
>   {
>     static _Atomic_word counter;
>     A()
>       {
> 	__gnu_cxx::__atomic_add(&counter, 1);
>       }
>     ~A()
>       {
> 	__gnu_cxx::__atomic_add(&counter, -1);
>       }
>   };
> 
> _Atomic_word A::counter = 0;
> 
> typedef std::shared_ptr<A> sp_A_t;
> typedef std::weak_ptr<A> wp_A_t;
> 
> typedef std::vector<sp_A_t> sp_vector_t;
> typedef std::vector<wp_A_t> wp_vector_t;
> 
> struct shared_and_weak_pools
> {
>   sp_vector_t& shared_pool;
>   wp_vector_t& weak_pool;
>   
>   shared_and_weak_pools(sp_vector_t& _shared_pool, wp_vector_t& _weak_pool)
>     : shared_pool(_shared_pool), weak_pool(_weak_pool)
>     { }
> };
> 
> void* thread_hammer_and_kill(void* opaque_pools)
> {
>   shared_and_weak_pools& pools = *static_cast<shared_and_weak_pools*>(opaque_pools);
>   // Using the same parameters as in the RNG test cases.
>   std::mersenne_twister_engine<
>     unsigned long, 32, 624, 397, 31,
>     0x9908b0dful, 11,
>     0xfffffffful, 7,
>     0x9d2c5680ul, 15,
>     0xefc60000ul, 18, 1812433253ul> rng;
>   
>   sp_vector_t::iterator cur_shared = pools.shared_pool.begin();
>   wp_vector_t::iterator cur_weak = pools.weak_pool.begin();
>   
>   for (unsigned int i = 0; i < HAMMER_REPEAT; ++i)
>     {
>       try
>       {
>         sp_A_t strong(*cur_weak);
>       }
>       catch (std::bad_weak_ptr& exception)
>       {
>         ++cur_weak;
>         if (cur_weak == pools.weak_pool.end())
>           break;
>       }
>       
>       if (rng() % KILL_ONE_IN == 0)
>       {
>         cur_shared->reset();
>         ++cur_shared;
>       }
>     }
>   return 0;
> }
> 
> void* thread_hammer(void* opaque_weak)
> {
>   wp_vector_t& weak_pool = *static_cast<wp_vector_t*>(opaque_weak);
>   // Using the same parameters as in the RNG test cases.
>   std::mersenne_twister_engine<
>     unsigned long, 32, 624, 397, 31,
>     0x9908b0dful, 11,
>     0xfffffffful, 7,
>     0x9d2c5680ul, 15,
>     0xefc60000ul, 18, 1812433253ul> rng;
> 
>   wp_vector_t::iterator cur_weak = weak_pool.begin();
> 
>   for (unsigned int i = 0; i < HAMMER_REPEAT; ++i)
>     {
>       try
>       {
>         sp_A_t strong(*cur_weak);
>       }
>       catch (std::bad_weak_ptr& exception)
>       {
>         ++cur_weak;
>         if (cur_weak == weak_pool.end())
>           break;
>       }
>     }
>   return 0;
> }
> 
> int
> test01()
> {
>   bool test __attribute__((unused)) = true;
>   sp_vector_t obj_pool(POOL_SIZE);
>   
>   for(sp_vector_t::iterator cur = obj_pool.begin(); cur != obj_pool.end(); ++cur)
>   {
>     cur->reset(new A);
>   }
>   // Obtain weak references.
>   std::vector<wp_vector_t> weak_pool(HAMMER_MAX_THREADS, wp_vector_t(obj_pool.begin(), obj_pool.end()));
>   
>   // Launch threads with pointer to weak reference.
>   pthread_t threads[HAMMER_MAX_THREADS];
> #if defined(__sun) && defined(__svr4__) && _XOPEN_VERSION >= 500
>   pthread_setconcurrency (HAMMER_MAX_THREADS);
> #endif
>   
>   pthread_attr_t tattr;
>   pthread_attr_init(&tattr);
> 
>   shared_and_weak_pools pools(obj_pool, weak_pool[0]);
>   pthread_create(threads, &tattr, thread_hammer_and_kill, static_cast<void*>(&pools));
>   for (unsigned int worker = 1; worker < HAMMER_MAX_THREADS; worker++)
>     {
>       if (pthread_create(&threads[worker], &tattr,
> 			 thread_hammer, static_cast<void*>(&weak_pool[worker])))
> 	std::abort();
>     }
>   // Wait for threads to complete, then check integrity of reference.
>   void* status;
>   for (unsigned int worker = 0; worker < HAMMER_MAX_THREADS; worker++)
>     {
>       if (pthread_join(threads[worker], &status))
> 	std::abort();
>     }
>   obj_pool.clear();
>   
>   VERIFY( A::counter == 0 );
>   
>   return 0;
> }
> 
> int 
> main()
> {
>   test01();
>   return 0;
> }

Jonathan,
    The test program when compiled as i386 randomly hangs under both the 32-bit and 64-bit
kernels on Darwin 10.3.0. I've emailed Mike Stump an Instruments trace file sampling the
hung binary. Unfortunately, I don't know how to convert that to a human readable form
to attach to a bug report. I'll open a bug report after Mike takes a look at the trace
(just to make sure this shouldn't be a radar report instead).
          Jack