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

El 28/05/2015 a las 21:02, Michael escribió:

On May 28, 2015 2:50:48 PM EDT, "Ion Gaztañaga" wrote:

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El 28/05/2015 a las 12:13, Niall Douglas escribió:

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On 27 May 2015 at 18:00, Ion Gaztañaga wrote:

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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.

On Windows you can mark a filing system entry as always deleted on close. Such an entry will be deleted on close no matter what, including power loss and filesystem corruption (the chkdsk with delete such still existing items).

If you therefore need a synchronisation object to exist only for this boot cycle and to always disappear in the next boot cycle, delete on close is an excellent way of doing it. Why the Windows Temp files don't default to delete on close is beyond me (you can also unset delete on close at any time on an open file handle).

Can you elaborate, please? What's a "filling system entry"?

Delete-on-close would delete the resource when the last attached process exits, so it would be deleted before system reboot a new processes could not connect to the resource. Or am I missing something?

Wouldn't it be a moot point when all mutex consumers closed? Next one fires up and requests a brand new round of shared mutex.

That could work with a mutex, half-work with a semaphore (the count should remain stable after the last process closes the handle) and broken for a shared memory object. The key is how to find a unique identifier that identifies each reboot. I've tried: -> kernel boot time. It changes when clock is adjusted -> WMI LastBootUpTime. A lot of problems with my poor implementation and problems after hibernation and clock changes. -> Look for event ID == 6005 (event log started) in the System event log: problems when too many events are appended to the log as that event is lost. Any ideas? Best, Ion