Re: Handling access to shared resources

From:

SG <s.gesemann@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Sun, 10 May 2009 00:18:57 -0700 (PDT)

Message-ID:

<f5fac843-8de3-4339-834c-1c39634b82b2@o20g2000vbh.googlegroups.com>

On 10 Mai, 08:48, Angus <anguscom...@gmail.com> wrote:

[...] accessed via different threads and I use a mutex lock/unlock
to ensure that only one process can work on the list at any one
time. The trouble is the lock and unlock is scattered through the
code. I am having problems where I do a lock but there is no unlock
and the code gets stuck. It is quite tricky to debug of course.

Does anyone have any tips on how to handle this problem. Should I use
some global/singleton accessor function to access the list? But I do
need to perhaps edit/delete/add to the list. so how best to handle?

You should make use of RAII for the locks. If you're using a C API for
threads you may want to write your own "lock" class that can be used
like this:

  void foo() {
    lock l (&mutex);
    // do something
  } // automatically unlock mutex in destructor of 'l'

This should be the preferred method for locking/unlocking mutexes.
Something like this is supported by the Boost.Threads library and will
be supported by the next C++ standard library.

Cheers!
SG