Re: [RFC][PATCH] request_irq(...,SA_BOOTMEM);

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

> I don't immediately see anything in there which would prevent us from
> running these:
> 
> 	vfs_caches_init_early();
> 	cpuset_init_early();
> 	mem_init();
> 	kmem_cache_init();
> 	setup_per_cpu_pageset();
> 
> just after sort_main_extable().
> 
> But things will explode ;)
> 
> I suggest you run up a patch, test it on whatever machines you have, send
> it over and I'll do the same.  But please make sure it has a config option
> to restore the old sequence for now.  a) So people can work out that it was
> this patch which broke things and b) so it doesn't adversely affect testing
> of other things too much.

Good ideas. I'll give these things a spin. One thing that may explode is
that all that code is running with local_irq_disable() (since local irqs
aren't enabled before init_IRQ()) and that means possible use of some
types of semaphores may trigger warn-on's (or worse as I think some
implementations of down_read() might even force-enable irqs).

But there is no fundamental reasons to do so ... that's the trick :) If
that happens, those semaphores are still ok as they should never get
into contention that early.

Anyway, I'll give it a spin on ppc and maybe x86 if I can find a victim
to test on here, and will send something.

Cheers,
Ben.