Re: [PATCH v2 1/4] os-posix: Add os_set_daemonize()

[Daniel P . Berrangé]

On Fri, Mar 04, 2022 at 11:20:39AM +0100, Kevin Wolf wrote:
> Am 04.03.2022 um 10:19 hat Daniel P. Berrangé geschrieben:
> > On Thu, Mar 03, 2022 at 05:48:11PM +0100, Hanna Reitz wrote:
> > > The daemonizing functions in os-posix (os_daemonize() and
> > > os_setup_post()) only daemonize the process if the static `daemonize`
> > > variable is set.  Right now, it can only be set by os_parse_cmd_args().
> > > 
> > > In order to use os_daemonize() and os_setup_post() from the storage
> > > daemon to have it be daemonized, we need some other way to set this
> > > `daemonize` variable, because I would rather not tap into the system
> > > emulator's arg-parsing code.  Therefore, this patch adds an
> > > os_set_daemonize() function, which will return an error on os-win32
> > > (because daemonizing is not supported there).
> > 
> > IMHO the real flaw here is the design of 'os_daemonize' in that it
> > relies on static state. If I see a call to a function 'os_daemonize()'
> > I expect to be daemonized on return, but with this design that is not
> > guaranteed which is a big surprise.
> > 
> > I'd suggest we push the condition into the caller instead of adding
> > this extra function, so we have the more sane pattern:
> > 
> >    if (daemonmize()) {
> >       os_daemonize()
> >    }
> 
> It's not as simple, the static daemonize variable is used in more places
> than just os_daemonize(). I'm not sure if it's worth changing how all of
> this works, but if we did, it would be a refactoring mostly focussed on
> the system emulator and an issue separate from adding the option to the
> storage daemon.

It isn't that difficult to do the refactoring needed, so I've just
sent a series that does the job and CC folks from this thread on it.

With regards,
Daniel
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