linux-kernel - Re: timing of module MODULE_STATE

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Date:	Mon, 31 Aug 2015 08:53:26 -0400
From:	"Frank Ch. Eigler" <fche@...hat.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: timing of module MODULE_STATE_COMING notifier

Hi, Rusty -

Thanks for your response!

> [...]
> > That patch also moved the MODULE_STATE_COMING notifier call to
> > complete_formation(), which is relatively early to its former
> > do_init_module() call site.  It now precedes the parse_args(),
> > mod_sysfs_setup(), and trace_module_load() steps.
> 
> Yes, parse_args() can enter the module, so you really want it before
> then.

Understood.  (Perhaps mod_sysfs_setup() could sneak in ahead.)

> > Was the latter part of the change intended & necessary?  It is
> > negatively impacting systemtap, which was relying on
> > MODULE_STATE_COMING being called from a fairly complete module
> > state - just before the actual initializer function call.

> Notifiers suck for stuff like this :( Module state has many steps,
> so my preference has been to open-code explicit hooks.  [...]

You mean something like the trace_module_load()?  (We will probably
experiment with hooking into that tracepoint instead of the notifier.)
A more hard-coded one with an in-kernel callee probably wouldn't help
module-resident clients like us.

- FChE
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