why must I have a boost::mutex for boost::condition_variable?

Question

I have the following code: where m_event is a boost::condition_variable

        boost::scoped_lock dummy;
        boost::unique_lock<boost::scoped_lock> lock(dummy); // TODO: see if dummy is correct
        m_event.wait(lock, [this] () {
            return !this ->m_enqueue.empty();
        });

I don't really need that dummy locker I just want the event to stop upon a certain boolean condition, do I not understand something?

Why am I forced to use the dummy lock?

(P.S. code works great..)

EDIT: In fact if I understood correctly, what I have in my class is a boost::mutex, let's call it m_mtx and obvious inserters to the m_enqueue.. so I am changing my implementation accordingly to the lock to lock on m_lock and then the inserters would only do:

boost::mutex::scoped_lock<boost::mutex> guard(m_lock);

make sense?

See [this previous answer](http://stackoverflow.com/questions/13099660/c11-why-does-stdcondition-variable-use-stdunique-lock) — ichramm, Jan 12 '14 at 18:19
@ichramm: That's a question! And [it's a subtly different one](http://stackoverflow.com/questions/13099660/c11-why-does-stdcondition-variable-use-stdunique-lock#comment17804829_13099660), at that... — Lightness Races in Orbit, Jan 12 '14 at 18:22

score 0 · Answer 1 · answered Jan 12 '14 at 18:19

0

timed_wait waits for a lock to be obtained, if it does so in time.

Without a lock, it can't do anything.

It seems to me you're abusing timed_wait.

answered Jan 12 '14 at 18:19

Lightness Races in Orbit

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timed_wait was recently added and is not releavnt, same question for wait – Alon Jan 12 '14 at 18:21
What do you mean it's "not relevant"? Your question is about it, is it not? – Lightness Races in Orbit Jan 12 '14 at 18:21
no, it's why I have to use the dummy mutex, if you remove the timeout all together, the question remains, I will edit – Alon Jan 12 '14 at 18:24
@Alon: Yeah, the timeout is not the important part of the question _or_ my answer. I don't really understand what you expect this function to do without a lock to work with. – Lightness Races in Orbit Jan 12 '14 at 19:04

why must I have a boost::mutex for boost::condition_variable?

1 Answers1