On 2010-09-06 23:49:45 +0200, Anthony Williams said:

Kraus Philipp <philipp.kraus@flashpixx.de> writes:

I'm new with boost thread, I have some problems.

I have got two methods, one for writing and one for reading my data and I would

do this thread-safe.

I have tried to do this with boost::unique_lock<boost::shared_mutex> lock(...),

but I have created a deadlock.

For example my methods are called within the threads and set / get data to /

from a ublas matrix.

How can I do both methods in the correct way thread-safe? 

boost::mutex m;

void setData( const size_t row, const size_t col, const size_t data) {

    boost::unique_lock<boost::mutex> lk(m);

    _matrix(row, col) = data 

}

void getData( const size_t row, const size_t col, size_t& a, size_t& b) {

    boost::unique_lock<boost::mutex> lk(m);

    a = _matrix(row, col);

    b = _matrix(col, row);

}

Once you've got the basics working, you can change the mutex to a

boost::shared_mutex and the lock in getData to a shared_lock rather than

a unique_lock if profiling determines that this is the bottle neck, *and*

the shared_mutex helps.

Thanks, but I have tried with the shared mutex like:

setData:

{

boost::unique_lock<boost::shared_mutex> lock( _matrixlock ); 

_matrix(row, col) = data 

}

getData:

{

boost::shared_lock<boost::shared_mutex> lock( _matrixlock );

 a = _matrix(row, col);

 b = _matrix(col, row);

}

I use the same lock mechanism for a ublas::vector<std::size_t> with a new mutex variable (_vectorlock), it seams there is an error. Is there a problem if I use two different mutex? I have got two member variables (the matrix and a vector) that must be thread-safe (not at the same time).

If I debug the executable with helgrind I'll get 

==939== Thread #1: Bug in libpthread: recursive write lock granted on mutex/wrlock which does not support recursion

==939==    at 0x513FC: pthread_cond_wait* (hg_intercepts.c:653)

==939==    by 0x19D3B7: boost::thread::join() (inlibboost_thread.dylib)

==939==    by 0x1683C: boost::thread_group::join_all() (in ./main)

==939==    by 0x17E6D: symmetric(std::vector<std::string, std::allocator<std::string> > const&, bool const&) (in ./main)

==939==    by 0x25D2: main (in ./main)

Thanks

Phil