Re: [Boost-users] [Thread] What do I #include?

From: Anthony Williams (anthony.ajw_at_[hidden])
Date: 2008-07-11 09:13:53

"Khandelwal, Amit" <amit.khandelwal_at_[hidden]> writes:

> The way I use mutex is to protect one shared resource. Here is sample
> code that I cooked up. I am not sure why you want to use a single mutex
> to protect multiple resources. However, if your use case demands it than
> wrap those resources in a class and have a mutex as a member variable of
> that class.  

> template <typename T, typename SEQUENCE = std::deque<T> >
> class tsqueue {
>
>         const T& front() {
>             boost::lock_guard<boost::mutex> lock(mutex);
>             std::cout << "Pop element: " << m_queue.front() <<
> std::endl;
>             return m_queue.front();
>         }
>
>         void pop() {
>             boost::lock_guard<boost::mutex> lock(mutex);
>             return m_queue.pop();
>         }

This code is not thread safe unless there is only one consumer. Though
each operation is safe, the front()/pop() model gives you a race
condition: some other thread may steal your element between the call
to front() and pop().

See
http://www.justsoftwaresolutions.co.uk/threading/implementing-a-thread-safe-queue-using-condition-variables.html
for a description of a thread-safe queue that uses a condition
variable to provide waiting and allows multiple consumers.

Anthony
-- 
Anthony Williams            | Just Software Solutions Ltd
Custom Software Development | http://www.justsoftwaresolutions.co.uk
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