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<== Date ==> <== Thread ==>

Subject: Re: Shutdown issues
From: Benjamin Franksen <[email protected]>
To: <[email protected]>
Date: Thu, 20 Nov 2014 10:57:50 +0100
On Wednesday 19 November 2014 10:59:10 Ralph Lange wrote:
> Since Michael had to take back some of the epicsExit() changes, I was
> thinking about how to do a smooth transition to a smarter IOC
> shutdown/restart.
>
> This is coming back to a suggestion that Andrew had a few months back:
> Do we need a staged shutdown process with hooks for each stage -
> similar to the initHooks mechanism?
>
> At that point there would also be a clearer definition of which stages
> are shut down for a "hot standby" or a "warm complete restart" of the
> IOC.
>
> Maybe the module could also declare its name and functionalities, e.g.
> as an or'ed mask of features like "supports_standby",
> "supports_restart", "supports_link_change", etc so that the IOC core
> can decide if and how to do restart/shutdown and can provide better
> diagnostics.
>
> So that instead of simply setting
>      epicsAtExit(func, arg);
>
> a module would set things along the line of
>      id = epicsExitRegister("myModule",
> supports_standby|supports_restart); epicsAddExitHook(id,
> EXIT_BEFORE_CORE, func1, arg1);
>      epicsAddExitHook(id, EXIT_BEFORE_SERVER, func2, arg2);
>      epicsAddExitHook(id, EXIT_BEFORE_DBSCAN, func3, arg3);
>      epicsAddExitHook(id, EXIT_BEFORE_ERRLOG, func4, arg4);
>
> Compatibility - epicsAtExit could do
>      {
>          bla = epicsExitRegister("$$filename$$", 0);
>          epicsAddExitHook(bla, EXIT_BEFORE_CORE, func, arg);
>      }
>
> What do you think?

Hi Ralph

Yes, definitely. Make the dependencies and the relative order explicit.
Even though it does add more code, such a change makes the whole
shutdown thing more predictable and easier to reason about.

Cheers
Ben
--
"Make it so they have to reboot after every typo." ― Scott Adams

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References:
Shutdown issues Ralph Lange

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