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List:       openbsd-tech
Subject:    Re: Unnecessary mmap flags?
From:       Theo de Raadt <deraadt () cvs ! openbsd ! org>
Date:       2014-06-28 2:26:37
Message-ID: 201406280226.s5S2QbLl010139 () cvs ! openbsd ! org
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> > MAP_HASSEMAPHORE is used in rthread_sem.c, but it doesn't do anything,
> > so I suspect it's just cargo culting based on man page misinformation?
> > Are there architectures that actually have restrictions on semaphore
> > memory?
> 
> There architectures where atomic instructions only work on pages with
> certain caching attributes.  Those attributes tend to be the default
> attributes though, so there is not much value in retaining this flag.

Whether such architectures exist and want to do atomic handling is one
thing.  The real question is if any applications set the flag.

Looks like no.

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