Re: [Xen-cim] Emailing: libxen.diff

[Gareth S Bestor <bestorga@xxxxxxxxxx>]

FYI - CMPI already has a dedicated Cleanup()
method that invoked whenever the CIMOM is about to unload a provider lib
(and you can prevent unloading by returning a specific return code), and
the means to add an optional init() method that is invoked immediately
after a provider lib is first loaded and before the first request is processed.
Will using these avoid some of the issues here?

- Gareth

Ewan Mellor <ewan@xxxxxxxxxxxxx>
Sent by: xen-cim-bounces@xxxxxxxxxxxxxxxxxxx

12/24/2006 06:50 AM

To	"Subrahmanian, Raj" <raj.subrahmanian@xxxxxxxxxx>
cc	xen-cim@xxxxxxxxxxxxxxxxxxx, Jim Fehlig <jfehlig@xxxxxxxxxx>
Subject	Re: [Xen-cim] Emailing: libxen.diff

On Sun, Dec 24, 2006 at 02:20:50AM -0500, Subrahmanian,
Raj wrote:

> Ewan,
> It looks like if we can just do these inside _init and _fini (which
are
> functions called when the library is loaded and unloaded respectively),
> we won't need to wory about MT-safeness. The OS won't unload the shared
> library till everyone who's linked to it has unloaded.
> Was there any specific reason why there were specific xen_init and
> xen_fini calls created?

Well firstly, _init and _fini are marked OBSOLETE/DANGEROUS on pages
like this:

http://tldp.org/HOWTO/Program-Library-HOWTO/miscellaneous.html

Secondly, they only apply to shared libraries -- if libxen were linked
statically with your application, this facility would not be available.

Having xen_init and xen_fini gives you the most flexibility -- if you
know that you're in a threaded environment, or are loading as a dynamic
module, then you can wrap them up appropriately, and if you're running
in a statically compiled program, then you can just call them at the top
and bottom of main().

For your particular problem, I think you just need to push the mutex up
into the CIM provider rather than libxen, and everything should be fine.

Ewan.

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