In message <20030502.204628.35664814.davem@xxxxxxxxxx> 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
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. */
/* Tell all freeze threads to disable interrupts halves. */
> 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(
Anyone who quotes me in their sig is an idiot. -- Rusty Russell.