On Tue, 17 June 2008 12:52:22 -0700, Tim Bird wrote:
> Jörn Engel wrote:
> > On Tue, 17 June 2008 11:23:18 -0700, Tim Bird wrote:
> >> I'm not that happy using an ioctl for this trigger. What is
> >> the preferred method of activating a kernel feature like this?
> >> I presume something in /proc or /sys, but I'm not sure.
> >
> > I personally would be unhappy with any kind of interface for this. It
> > would be much nicer to make it transparent and still get the benefits.
> > One option would be to start a kernel thread for the initialization and
> > renice it to 19 or so.
>
> That's an interesting idea. I'm pretty sure the product guys want
> an explicit trigger, so they can make sure they've got the main
> application well underway before this deferred initialization occurs.
Well, there should be a way to ensure this doesn't hog the cpu at all -
unless it is idle or someone is actually waiting for the initialization
to finish. Not sure if nice 19 is good enough for that.
> > If you want an explicit trigger, you could either hook into init_post()
> > or have hooks in the open functions of drivers with deferred
> > initialization.
>
> This would presumably require multiple calls (one to the open of
> each deferred module). I would still need a trigger for the memory
> free operation, unless I hardcode the order of the opening and just
> "know" that the last one should free the memory. I'll have to see
> if all the modules being loaded like this have open()s.
If you want to keep things simple - and I believe initially you should -
you can simply do all initializations in one go. Something like this:
int foo_open(...)
{
wait_for_deferred_init();
...
}
static DECLARE_COMPLETION(init_complete);
void wait_for_deferred_init(void)
{
static atomic_t in_progress = ATOMIC_INIT(-1);
if (!atomic_inc_not_zero(in_progress) {
wait_for_completion(init_complete);
return;
}
for (all deferred initcalls)
foo_init();
complete(init_complete);
free_memory();
}
Jörn
--
Anything that can go wrong, will.
-- Finagle's Law
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