Re: [Boost-users] [IPC Named Mutex]

Subject: Re: [Boost-users] [IPC Named Mutex]
From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2015-05-28 14:47:19

El 28/05/2015 a las 1:25, Gavin Lambert escribió:
> On 28/05/2015 04:00, Ion Gaztañaga wrote:
>> El 26/05/2015 a las 8:08, Gavin Lambert escribió:
>>> Given that the failure was somewhere related to directory names, what's
>>> probably happening is that it's trying to find the name of its shared
>>> directory.  For that it evidently wants to use the boot time, as it's a
>>> value that should be identical for all processes started since the last
>>> reboot, but different between reboots (to avoid getting stale data).
>>
>> Yes, that's the idea. Obtaining this "unique" identifier between reboots
>> that remains stable between all processes it's been incredibly
>> difficult. Any alternative or suggestion is welcome.
>
> Use CreateFileMapping to create a named (simple constant name) mapping
> *not* backed by a file.  Store whatever data you want in here; this can
> include a randomly-generated value used to look up other items if you
> wish (generated by the first process to create the mapping and then used
> by all subsequent processes -- you may need to use a mutex either within
> the mapping or via CreateMutex to resolve races if multiple processes
> simultaneously access the mapping for the first time).

If all processes close the mapping, that mapping disappears and 
Interprocess shared memory must have kernel lifetime (POSIX semantics). 
SEe 
http://www.boost.org/doc/libs/1_55_0/doc/html/interprocess/some_basic_explanations.html#interprocess.some_basic_explanations.persistence

We need something that remains stable even if all processes using it are 
killed, launch a new one and connect to this resource. Only after the 
machine is rebooted the resource disappears.

Ion