Re: [boost] [thread] Exception based timed locks

Subject: Re: [boost] [thread] Exception based timed locks
From: vicente.botet (vicente.botet_at_[hidden])
Date: 2009-01-19 19:47:51

----- Original Message ----- 
From: "vicente.botet" <vicente.botet_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Tuesday, January 20, 2009 1:03 AM
Subject: [boost] [thread] Exception based timed locks

> 
> Hi,
> 
> I've read recently about timed locks throwing an exception when there is a timeout.
> What do you think about this behaviour?
> Could the thread library provide both?
> 
> Next follows a piece of code without exceptions
> 
>    while (polling) {
>        t=now()+100;
>        boost::unique_lock<boost::mutex> l1(m1, t);
>        if (l1.has_lock() {
>            boost::unique_lock<boost::mutex> l2(m2, t);
>            if (l2.has_lock() {
>                boost::unique_lock<boost::mutex> l3(m3, t);
>                if (l2.has_lock() {
>                    foo();
>                    polling = false;
>                } else execute_on_failed(); 
>            } else execute_on_failed(); 
>        } else execute_on_failed(); 
>    }
> 
> and now with exceptions
> 
>    while (polling)
>        try {
>            t=now()+100;
>            boost::exception_unique_lock<boost::mutex> l1(m1, t);
>            boost::exception_unique_lock<boost::mutex> l2(m2, t);
>            boost::exception_unique_lock<boost::mutex> l3(m3, t);
>            foo();
>            polling = false;
>        } catch (timeout_exception& ex) {execute_on_failed(); }
> 
> What do you think about a try_lock_until, try_lock_for functions
> 
>    while (polling)
>        try {
>            boost::try_lock_for(100, m1, m2, m3);
>            foo();
>            polling = false;
>        } catch (timeout_exception& ex) {execute_on_failed(); }
> 

Sorry, in order to be exception safe we need a kind of scoped lock for tuples

    while (polling)
    try {
        exception_unique_lock_tuple<mutex, shared_mutex, mutex>(100, m1, m2, m3);
        foo();
        polling = false;
    } catch (timeout_exception& ex) {execute_on_failed(); }

Independent of the exception timeout, what do you think of a unique_lock_tuple?

Regards,
Vicente