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Date: Wed, 22 Nov 2000 22:34:55 +1100
From: Andrew Morton <andrewm@uow.edu.au>
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To: David Woodhouse <dwmw2@infradead.org>
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Subject: Re: hardcoded HZ in hub.c
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David Woodhouse wrote:
> 
> andrewm@uow.edu.au said:
> >  Nothing which sleeps for very long - mainly serial drivers which
> > queue a call to tty_hangup(), which immediately queues _another_
> > tq_scheduler call to do_tty_hangup (Why?  Heaven knows).
> 
> Not so much worried about that. More about how sensitive they would be to
> something _else_ causing the eventd thread to sleep for 'multiple seconds'
> before getting round to doing what they asked.

Ah.  No, I don't think it would be polite to cause TTY hangup processing
to be deferred for this long.  I'd suggest that the policy be "scheduled
tasks can't sleep".  I guess kmalloc(GFP_KERNEL) is acceptable because
the system is already running like a dog if this sleeps.

> I really don't want to have to start using multiple eventd threads before
> 2.5, if at all. So I don't want to add the USB hub stuff unless the other
> queued tasks will be happy with that.

Some of these requirements could also be satisfied with a combination of
a timer_list and a tq_struct.  When the timer fires, feed the tq_struct
into schedule_task.

Easy, except for the problem of killing the damn things off reliably.  That
would require a bit of infrastructure.  But it's the right thing for
netdriver media polling functions, for example.
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