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    <p>Check out <strong>Herb Sutter</strong> talk at <strong>C++ and Beyond 2012</strong>: <a href="http://channel9.msdn.com/Shows/Going+Deep/C-and-Beyond-2012-Herb-Sutter-Concurrency-and-Parallelism" rel="nofollow">C++ Concurrency</a>. He shows example of <a href="http://en.wikipedia.org/wiki/Monitor_%28synchronization%29" rel="nofollow">Monitor Object</a>-like implementation in C++11.</p> <pre><code>monitor&lt;Account&gt; m[2]; transaction([](Account &amp;x,Account &amp;y) { // Both accounts are automaticaly locked at this place. // Do whatever operations you want to do on them. x.money-=100; y.money+=100; },m[0],m[1]); // transaction - is variadic function template, it may accept many accounts </code></pre> <p>Implementation:</p> <p><a href="http://coliru.stacked-crooked.com/a/de69939cf1ec890d" rel="nofollow"><strong>LIVE DEMO</strong></a></p> <pre><code>#include &lt;iostream&gt; #include &lt;utility&gt; #include &lt;ostream&gt; #include &lt;mutex&gt; using namespace std; typedef int Money; struct Account { Money money = 1000; // ... }; template&lt;typename T&gt; T &amp;lvalue(T &amp;&amp;t) { return t; } template&lt;typename T&gt; class monitor { mutable mutex m; mutable T t; public: template&lt;typename F&gt; auto operator()(F f) const -&gt; decltype(f(t)) { return lock_guard&lt;mutex&gt;(m), f(t); } template&lt;typename F,typename ...Ts&gt; friend auto transaction(F f,const monitor&lt;Ts&gt;&amp; ...ms) -&gt; decltype(f(ms.t ...)) { return lock(lvalue(unique_lock&lt;mutex&gt;(ms.m,defer_lock))...), f(ms.t ...); } }; int main() { monitor&lt;Account&gt; m[2]; transaction([](Account &amp;x,Account &amp;y) { x.money-=100; y.money+=100; },m[0],m[1]); for(auto &amp;&amp;t : m) cout &lt;&lt; t([](Account &amp;x){return x.money;}) &lt;&lt; endl; } </code></pre> <p>Output is:</p> <pre><code>900 1100 </code></pre>
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    1. POWhat's the proper way to associate a mutex with its data?
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    1. USEvgeny Panasyuk
    1. USEvgeny Panasyuk
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    1. POWhat's the proper way to associate a mutex with its data?
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    1. COI think this code, in and of itself, can deadlock if money is transferred from A to B and from B to A at the same time. My code has the same problem, but, as I noted in a comment above, it can be easily eliminated by using `std::lock`. That doesn't seem to be possible here, because there is no part of the code that knows that two mutexes need to be locked.
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    2. CO@KnowItAllWannabe, I do use **std::lock** "lock(lvalue(unique_lock<mutex>(ms.m,defer_lock))...)". **transaction** function knows that two mutexes should be locked. (it is updated answer version)
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    3. COIn concept, I like what you're doing here, but it will take me a bit of time to really think it through. I like the generalization of `transaction` to work with an arbitrary number of objects, but I think there may be some details to tidy up as regards `const` correctness (e.g., it looks to me like `ms` should be passed as lref-to-`const`. I plan to follow up again tomorrow.
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