Re: [Boost-users] Compatibility between shared_ptr and Rational RoseRT

From: Caleb Epstein (caleb.epstein_at_[hidden])
Date: 2005-04-26 16:52:05

On 4/26/05, Ross Manges <ross.manges_at_[hidden]> wrote:

> > Attaching the code (in whatever form is convenient to you) is fine.
> OK, I've attached some sample code I made up to show the kind of problems
> I'm having (the code doesn't do anything useful).  Running this code
> results in the backtrace below.  I am aware that this code breaks the
> condition that the shared_ptr needs to have exclusive writing
> modifications; however, I am unsure how to fix the code to make it
> correct.  Please let me know if you have any suggestions, thanks! (BTW,
> I'm running against the Boost CVS which I downloaded on Fri, Apr 22nd; if
> I run against version 1_32, the backtrace is in the scope_lock instead of
> atomic_increment)
> 
> some info about my system:
> Red Hat Enterprise Linux 3, running 2.4.21-4.ELsmp
> (on a dual-processor dell with xeon's, if that matters)
> 
> and here's the backtrace:
> (gdb) bt
> #0  0x0804a703 in atomic_increment (pw=0x21006) at
> sp_counted_base_gcc_x86.hpp:59
> #1  0x0804a655 in boost::detail::sp_counted_base::add_ref_copy
> (this=0x21002) at sp_counted_base_gcc_x86.hpp:133
> #2  0x0804a4d7 in boost::detail::shared_count::operator= (this=0xb191cde8,
> r=@0xb731e004) at shared_count.hpp:181
> #3  0x08049a58 in boost::shared_ptr<Element>::operator= (this=0xb191cde4,
> r=@0xb731e000) at shared_ptr.hpp:148
> #4  0x0804b089 in SimpleQueue::pop (this=0x804f290) at ../SimpleQueue.cpp:22
> #5  0x080494ef in CommonThread::operator() (this=0x8050470) at
> ../CommonThread.cpp:11
> #6  0x0804a06d in
> boost::detail::function::void_function_obj_invoker0<CommonThread,
> void>::invoke (function_obj_ptr=
>       {obj_ptr = 0x8050470, const_obj_ptr = 0x8050470, func_ptr =
> 0x8050470, data = "p"}) at function_template.hpp:136
> #7  0xb75ce283 in boost::thread_group::size ()
>    from
> /home/auser/devel/boost_cvs_install/lib/libboost_thread-gcc-mt-1_32.so.1.32.0
> #8  0xb7493e21 in pthread_start_thread () from /lib/i686/libpthread.so.0
> #9  0xb743208a in clone () from /lib/i686/libc.so.6

In SimpleQueue::pop, you call Queue.empty() without locking the mutex.
 Move your scoped lock before the if (!Queue.empty ()) check and all
is well.  I've verified this on a 2-way Xeon box running an
almost-identical kernel.

-- 
Caleb Epstein
caleb dot epstein at gmail dot com