Re: [Boost-users] interprocess_condition::wait(scoped_lock<interprocess_upgradable_lock> &) missing

Subject: Re: [Boost-users] interprocess_condition::wait(scoped_lock<interprocess_upgradable_lock> &) missing
From: John Ky (newhoggy_at_[hidden])
Date: 2011-02-02 23:01:00

Oops.  Left some name mangling in there.  Fixed now.

On 3 February 2011 12:16, John Ky <newhoggy_at_[hidden]> wrote:

> Hi boost users,
>
> I've discovered that the following doesn't compile.
>
>    using namespace boost::interprocess;
>    interprocess_upgradable_mutex mutex;
>    interprocess_condition cv;
>    boost::posix_time::ptime deadline;
>
>    {
>       scoped_lock<interprocess_upgradable_mutex> lock(mutex);
>       sharable_lock<interprocess_upgradable_mutex> lock2(mutex);
>       cv.wait(lock); // doesn't compile
>       cv.timed_wait(lock, deadline); // doesn't compile.
>    }
>
> It is failing because boost doesn't define the following methods:
>
>    void interprocess_condition::do_wait(interprocess_upgradable_mutex
>  &mut);
>
>    bool interprocess_condition::do_timed_wait(const
> boost::posix_time::ptime &abs_time, interprocess_upgradable_mutex &mut);
>
> I was thinking of making a basic implementation like so:
>
> Define a scoped_unlock class, which behaves just like scoped_lock except
> the constructor unlocks and the destructor locks.
>
> Then define the following:
>
> inline void interprocess_condition::do_wait(interprocess_upgradable_mutex
> &mut)
> {
>    scoped_unlock<interprocess_upgradable_mutex> unlock(mut);
>    interprocess_mutex &internal_mutex = mut.m_mut;
>    scoped_lock<interprocess_mutex> internal_lock(internal_mutex);
>    this->wait(internal_lock);
> }
>
> inline bool interprocess_condition::do_timed_wait
>    (const boost::posix_time::ptime &abs_time, interprocess_upgradable_mutex
> &mut)
> {
>    scoped_unlock<interprocess_upgradable_mutex> unlock(mut);
>    interprocess_mutex &internal_mutex = mut.m_mut;
>    scoped_lock<interprocess_mutex> internal_lock(internal_mutex);
>    return this->timed_wait(internal_lock, abs_time);
> }
>
>
> These functions simply do the following:
>
>    - unlock the exclusive lock on the interprocess_upgradable_mutex (which
>    is emulated with an internal interprocess_mutex)
>    - then lock the internal interprocess_mutex
>    - Call interprocess_condition::wait or interprocess_condition::time_
>    wait on the implementation lock which does all the work
>    - unlock the internal interprocess_mutex
>    - relock the exclusive lock on  the interprocess_upgradable_mutex
>
> Intuitively, this should work.
>
> Is there anything I missed that would make this an incorrect
> implementation?
>
> Cheers,
>
> -John
>
>