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Re: Shared-Memory for the Hurd?

From: Marcus Brinkmann
Subject: Re: Shared-Memory for the Hurd?
Date: Fri, 5 Jan 2001 16:41:42 +0100
User-agent: Mutt/1.1.4i

On Fri, Dec 01, 2000 at 04:01:47AM +0100, Farid Hajji wrote:
> 5.) fullsized translator, providing pseudo-filesystem:
>   * each shm-segment is represented by a pseudo-file managed by a
>     fullsized translator settrans on e.g. /shm. The translator manages
>     vm_allocate()ed pages just like in 3.) and 4.), mapping them to
>     the pseudo-files [that is: shm-segment 34343 is mapped to /shm/34343].

Yes, this is a way to go. This could be a derivative of tmpfs, providing
only a flat directory (Roland suggested /var/run/sysvshm) and only accepts
certain file names coresponding to a key_t != 0 "with a funny behaviour
about unlinking open files so the SHM_RMID behaviour is right." (Roland).

Farid, this is an excellent medium sized project to dive into the Hurd
inners. Are you still interested in implementing this?

> Notes:
>   * shm-segments are visible as plain [pseudo-] files and could also
>     be mmap()-ed, or read()/write()... from other processes that have
>     enough permissions.

Yes, mmap() would be ideal.

> 5. same as in 4, but much more harder to implement, since there
>    is no good template/hello for a full filesystem translator in
>    the Hurd right now (besides full-blown ext2, ufs).
>    -> What about /procfs translator? Someone wrote such a beast,
>       but it is not in CVS. Where to get it please?

Well, tmpfs should be a good start. It isn't functional currently and not
tested, but there are only small changes necessary to make it work (coming
soon). tmpfs uses virtual memory to store the files.


`Rhubarb is no Egyptian god.' Debian
Marcus Brinkmann              GNU

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