Messages in this thread | | | From | Daniel Phillips <> | Subject | Re: [PATCH] fix remap of shared read only mappings | Date | Fri, 5 Sep 2003 02:49:21 +0200 |
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On Friday 05 September 2003 00:33, James Bottomley wrote: > On Thu, 2003-09-04 at 17:48, Jamie Lokier wrote: > However, POSIX does imply levels of cache coherence for both MAP_SHARED > and MAP_PRIVATE: > > With MAP_SHARED, any change to the underlying object after the mapping > must become visible to the mapper (although the change may be delayed by > local caching of the changer's implementation until it is explicitly > flushed).
This an interesting tidbit, as I'm busy working on a DFS mmap for OpenGFS, and I want to be sure I'm implementing true-blue Posix semantics. But trawling through the Posix/SUS specification at:
http://www.unix-systems.org/version3/online.html
all it says is that for MAP_SHARED "write references shall change the underlying object." I don't see anything about when those changes become visible to other mappers, much less any discussion of local caching. Am I looking at the wrong document?
Regards,
Daniel
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