Re: [RFC] 4KB stack + irq stack for x86

[Linus Torvalds]

On Wed, 5 Jun 2002, Benjamin LaHaise wrote:
> 
> Ah, you're right.  If anyone uses current_thread_info from IRQ context 
> it will set the flags in the wrong structure.  However, it actually 
> works because nobody does that currently: all of the _thread_flag users 
> appear to be coming in from task context.  Mostly that's luck as I 
> didn't change the smp ipis to switch stacks, so the only place that 
> is an interrupt and needs to access the actual thread data, does.

Hmm..

How about just making the interrupt code (ie do_IRQ()) or in the flags 
into the "parent" flags.

All of the flags should be "sticky one-bits", so just oring them should do 
the right thing.

That way we don't have to add nasty BUG checks to the code, and since 
we're already dirtying both cache-lines the extra overhead should 
literally be just the cost of doing one locked "orl".

			Linus