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SubjectRe: Lockups - lost interrupt
On Mon, Sep 13, 1999 at 05:41:31PM +0200, mingo@chiara.csoma.elte.hu wrote:
> > My feeling is that the cost is undetectable [...]
>
> i understand what you mean, but Linux kernel's speed is a 'sum' of many
> such 'undetectable' improvements. You cannot remove any of those speedups
> just because the speedup is undetectable.

Sure. That's why it should be a config unless we can figure out
this table idea. I'll have to look at the exceptions code -- but I
think there are some jumps necessary.

>
> > [...] and that if you don't want
> > rtl you run standard code, if you do want, you run a jump table that
> > allows rtl to be turned on and off.
> >
> > But I do like the idea of a section, I just don't know how to do it
> > wouldnt it compile out to similar code ?
> > ...
> > jmp 1f
> > .section cli_stuff
> > 1: cli
> > .section text
> > ...
>
> thats the hard part i think too. One way to do it is like for exceptions
> (check out how exceptions build their tables, Documentation/exception.txt)
> : patch int3 into the necessery places if RT is enabled (int3 [or
> equivalent] in this case is a full replacement for all 4 type of
> instructions, cli, sti, popfl and pushfl), then search the 'exception
> table' for the address. (the return address is pushed onto the stack by

int3 for cli
int4 for sti
int5 for pushfl
int6 for popfl

> int3) This search can be rather slow though, and thats the main problem i
> think. There is no cost to the main kernel, apart from the (presumably not
> very big) kernel-resident address-tables.
>
> -- mingo

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