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QNX Operating System/Discussion/OSTech/shared memory persistence/List of Posts
Forum Topic - shared memory persistence: (4 Items)
   
Update
David Zhao
03/12/2008 1:33 AM
post5721
shared memory persistence   
Hello, qnx experts,

In qnx, dose the shared memory object(SMO) ever have a chance to be written to stable storage? 

We want to write some trash bytes to the SMO file and sync it before we unlink it to secure the information inside it, 
but fsync is not implemented for SMOs on QNX, so dose this mean that after the SMO is unlinked, the information it 
contains may still exist on some stable storage?

Thanks.

--david
Mario Charest
03/12/2008 10:20 AM
post5730
Re: shared memory persistence   
> Hello, qnx experts,
> 
> In qnx, dose the shared memory object(SMO) ever have a chance to be written to
>  stable storage? 
> 
> We want to write some trash bytes to the SMO file and sync it before we unlink
>  it to secure the information inside it, but fsync is not implemented for SMOs
>  on QNX, so dose this mean that after the SMO is unlinked, the information it 
> contains may still exist on some stable storage?
> 
> Thanks.
> 
> --david


Yes, as long as someone as it open it will not be "unlinked".  Note that after it's unliked it becomes invisible an 
nobody else can open it, but it will still exists as long it is open by at least one client.
David Zhao
03/18/2008 10:55 PM
post5925
Re: shared memory persistence   
OK, then do I have any way to sync the shared memory object on qnx? I tried fsync, and turned out fsync is not 
implemented for shared memory object. Are there any other functions that I can use to sync the qnx shared memory object?


Thanks.
--david
Colin Burgess(deleted)
03/18/2008 11:06 PM
post5926
Re: shared memory persistence   
If the shared memory object is backed by a file, and the filesystem supports mmap(), then
you can use msync() to flush the changes to the mapping back to the persistent file.

Note this was only supported in 6.3.2 and later.

Colin

David Zhao wrote:
> OK, then do I have any way to sync the shared memory object on qnx? I 
> tried fsync, and turned out fsync is not implemented for shared memory 
> object. Are there any other functions that I can use to sync the qnx 
> shared memory object?
> 
> Thanks.
> --david
> 
> _______________________________________________
> OSTech
> http://community.qnx.com/sf/go/post5925
> 

-- 
cburgess@qnx.com

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