Re: [boost] [interprocess] linux porting problems

From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2006-12-08 15:20:39

Hi Daren,
> Hi Ion,
> 
> I mananged to get something working on Linux by doing a try-catch block on 
> an "open_only" shmem object. It works fine on normal program exit. However, as 
> you probably know, if the program is killed or crashed there is a dangling 
> reference since remove/shm_unlink is never called.
> 
> So I'm wondering:
> 1) is there any way around this behavior on a kill/crash?

I haven't found a solution. Interprocess' ancestor, Shmem, emulated 
reference counted semantics in Linux trying to be similar to Windows, 
but I couldn't manage crashes. So Interprocess took a different 
approach: Linux persistence for Windows shared memory. Current 
Interprocess persistence semantics are explained in the documentation here:

http://ice.prohosting.com/newfunk/boost/libs/interprocess/
doc/html/interprocess/some_basic_explanations.html
#interprocess.some_basic_explanations.persistence

> 2) is there a way to manually remove the shared memory besides rebooting? (i 
> tried using ipcrm but it looks like it still thinks there are processes 
> attached).

Memory is created using POSIX shm_open() so it's platform defined if the 
shared memory is visible in the filesystem. In Linux, I think that 
shared memory is created in /dev/shm. You can use shell's "rm 
/dev/shm/file" to get the same behavior as shm_unlink().

If you find a way to manage crashes, I would be really, really happy. I 
revised several portable run-time implementations (apache, cygwin, 
etc...) but no-one, as far as I know has solved this.

Regards,

Ion