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

From: Linus Torvalds (torvalds@transmeta.com)
Date: Wed Jun 05 2002 - 13:53:10 EST


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

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