Re: [Boost-users] Named mutex..

From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2008-05-20 10:06:30

Jason Robertson wrote:
> Hi,
> I'm trying to create simple locks based on a string name.  I looked at the interprocess
 >module which has a named mutex,but it seems not well suited/efficient 
for use in a single
 > process, though I know it's supposed to work.

I don't recommend using Interprocess named mutex. It has different 
lifetime semantics than intra-process named mutexes and it can be less 
efficient than other mutexes.

I don't know about the Named Mutex pattern, but this pattern seems a bit 
resource expensive (creating and destroying mutexes on the fly). 
Wouldn't be better just to store the mutexes in the map without seeing 
if a client has destroyed it and re-create it again?

Regards,

Ion

> Instead, I'm just creating a map<string,weak_ptr<mutex>> in a NamedMutexManager class. 
 >It's used as a singleton and uses brute force locking to implement a 
named lock pattern.
 > Main method is
> shared_ptr<mutex> GetMutex(string name) {
> BigLock (only one thread at a time can get a lock so we synchronize access to map)
> check map
>     if we have entry, make sure weak_ptr hasn't been reclaimed
>         If so, make a new shared_ptr, save weak_ptr by name, return shared_ptr
>         If not, return shared_ptr copy from weak_ptr.lock()
>     If we habe no entry,
>         make a new shared_ptr, save weak_ptr by name, return shared_ptr
> }
> I'm just getting back to C++ after years, so I'm 99% sure there's probably a much better way.
 > Is there a better way to do an intra-process, reliable mutex by 
std::string name so I can
 > lock things by name?  How are other people doing this, do you find
 > interprocess:named_mutex suitable for use in-process?
 > I had problems with it.
> Thanks!
> Jason