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

[Corey Minyard <minyard@acm.org>]

Andrew Morton wrote:

>Corey Minyard <minyard@acm.org> 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