Hmm...I don't know why you say that there will be a race condition. Let
say 2 threads are calling pop on the queue and another thread is calling
front(). Let us call these 3 thread p1, p2 (for pop) and f1 for front.
As per my understanding - this could be one possible scenario.
P1 -- acquire the lock
P2 -- blocked on the lock
F1 -- blocked on the lock
P1 -- done and waiting on the lock
P2 -- still blocking
F1 -- acquired the lock
So where is the race condition ?
-----Original Message-----
From: boost-users-bounces@lists.boost.org
[mailto:boost-users-bounces@lists.boost.org] On Behalf Of Anthony
Williams
Sent: Friday, July 11, 2008 9:14 AM
To: boost-users@lists.boost.org
Subject: Re: [Boost-users] [Thread] What do I #include?
"Khandelwal, Amit"
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
class tsqueue { const T& front() { boost::lock_guardboost::mutex lock(mutex); std::cout << "Pop element: " << m_queue.front() << std::endl; return m_queue.front(); }
void pop() { boost::lock_guardboost::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-s afe-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 Registered in England, Company Number 5478976. Registered Office: 15 Carrallack Mews, St Just, Cornwall, TR19 7UL _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - This message is intended only for the personal and confidential use of the designated recipient(s) named above. If you are not the intended recipient of this message you are hereby notified that any review, dissemination, distribution or copying of this message is strictly prohibited. This communication is for information purposes only and should not be regarded as an offer to sell or as a solicitation of an offer to buy any financial product, an official confirmation of any transaction, or as an official statement of Lehman Brothers. Email transmission cannot be guaranteed to be secure or error-free. Therefore, we do not represent that this information is complete or accurate and it should not be relied upon as such. All information is subject to change without notice. -------- IRS Circular 230 Disclosure: Please be advised that any discussion of U.S. tax matters contained within this communication (including any attachments) is not intended or written to be used and cannot be used for the purpose of (i) avoiding U.S. tax related penalties or (ii) promoting, marketing or recommending to another party any transaction or matter addressed herein.