Re: Patch to fix race between the NMI code and the CMOS clock

[Corey Minyard]

Andrew Morton wrote:

> Corey Minyard <minyard@xxxxxxx> wrote:
>  
>
> > This patch fixes a race between the CMOS clock setting and the NMI
> > code.  The NMI code indiscriminatly sets index registers and values
> > in the same place the CMOS clock is set.  If you are setting the
> > CMOS clock and an NMI occurs, Bad values could be written to or
> > read from the CMOS RAM, or the NMI operation might not occur
> > correctly.
> >
> > Fixing this requires creating a special lock so the NMI code can
> > know its CPU owns the lock an "do the right thing" in that case.
> >    
>
> hm, tricky patch.  I can't see any holes in it.  The volatile variable is
> awkward but should be OK on x86 and I can see the need for it.
>  
It took some thought and I couldn't think of anything simpler.  I posted 
in on lkml a little while ago, and some people tried but nobody else 
found a simpler solution that worked with SMP.

> There's a preposterous amount of inlining happening in this code.  Hence
> your patch took the size of drivers/char/rtc.o from
>
>   text    data     bss     dec     hex filename
>   3657     540       8    4205    106d drivers/char/rtc.o
> to
>   5419     540       8    5967    174f drivers/char/rtc.o
>
> Do you think you could take a look at uninlining everything sometime?
>  
Certainly.  I'll try to have it sometime today.

Thanks,

-Corey
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