Re: dev->destructor

In message [ref] you write:

I think it can work Rusty, in short you create 1 freeze thread
per cpu.  You wake up all the freeze threads on non-local cpus,
and they indicate their presence via some bitmask.

This code is already in module.c.  I'm glad you like it though 8).

But we disable local irqs as well: this is what I call a "bogolock"
(the read-side of a bogolock is prempt_disable()/preempt_enable(): you
could temporarily disable preemption and force the scheduler to run
every preempted thread, and remove this).

This means the local master cpu executes the unload sequence.  It may
sleep in order to yield to, for example, semaphore holders, it may
also sleep to yield to kswapd and friends for the sake of memory
allocation.  I mean... consider all the situations and please try to
find some hole in this.  We can make all try_to_*() sleep at this
time too... this in particular needs more thought.

Well, it's a big task.  Holding interrupts disabled for unbounded time
on CPUs needs to be thought about, but I think can be fixed.  try_xxx
can be called from interrupt context: you really want to get rid of
interrupts, too...

During previous discussions, I called this "return to primordial
soup": back to like during init.  Ideally, only userspace context (no
interrupts, timers, bottom halves), and life is easy.

To make these freeze threads globally useful, we allow them to
run atomicity commands.  The two defined commands are "local_irq_*()"
and "local_bh_*()", two bitmasks control this and the freeze threads
check the bits in their spin loops.

Something like this?

	/* Tell all freeze threads to disable bottom halves. */
	void global_bh_disable(void);
	void global_bh_enable(void);

	/* Tell all freeze threads to disable interrupts halves. */
	void global_irq_disable(void);
	void global_irq_enable(void);

Do you see?  Maybe... it is nearly Nirvana! :-)))))

Yes, but I worry it might be an illusion 8)

Our ability to implement this changes the rest of the conversation,
so let us resolve this first.

Yes, but it's a big IF.  I think it might be easier to make all
unregistrations runnable in interrupt context 8(

Rusty.
--
  Anyone who quotes me in their sig is an idiot. -- Rusty Russell.