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Re: cross-process timeoutable semaphores
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Re: cross-process timeoutable semaphores



On 11 Nov 2009, at 22:18, Tyler Sample wrote:

> I'm trying to port some linux code to OSX, and have the need for a cross-process timeoutable semaphore (semtimedop in particular being in the original code).  This has been extremely frustrating and I'm about two weeks into trying to implement this basic mechanism (that took me about 2 hours to port from win32 to linux originally).

[snip]

> My last attempt has been using mach semaphores.  My problem there is poor documentation.  Even after studying mach and its various headers for a couple solid days, I just have no idea how to say to interested processes (which are anonymous, although with significant work I could probably change that) "here's the global port/semaphore name...request the access you need."  I'm really not sure how well it will work since only one task/process can have receive rights on a semaphore/port at the same time anyway.

Hi Tyler,

I think you might find the following blog post (which I just wrote) interesting:

  <http://alastairs-place.net/2009/11/cross-process_s/>

It's supposed to be a very simple example of how one might go about achieving what you were asking for here using the Mach APIs, which, as you point out, are a little difficult to "get" at first.  The book "Programming under Mach" is quite a handy reference, as is Amit Singh's "Mac OS X Internals: A Systems Approach".

Not entirely sure what Apple's people would say about this; IIRC they have said once or twice that use of the Mach API by third-parties is "discouraged", but in this particular instance it seems to be a reasonable solution to your specific problem.

Kind regards,

Alastair.

--
http://alastairs-place.net



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