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SubjectRe: [ACPI] ACPI global lock macros
Yu, Luming wrote:
>
>
> Above code have a bug! Considering below code:
>
> u8 acquired = FALSE;
>
> ACPI_ACQUIRE_GLOBAL_LOC(acpi_gbl_common_fACS.global_lock, acquired);
> if(acquired) {
> ....
> }
>
> Gcc will complain " ERROR: '%cl' not allowed with sbbl ". And I think any other compiler will
> complain that too !

Oops - the version I posted differed in one character from the version
that I'd compiled - I'd just used "sbb" in the working version and let
the compiler figure out which version to use.

>
> How about below changes to your proposal code.
>
> < "sbbl %0,%0" \
> < :"=r"(Acq):"r"(GLptr),"i"(~1L):"dx","ax"); \
> ---
>
>> "sbbl %%eax,%%eax" \
>> :"=a"(Acq):"r"(GLptr),"i"(~1L):"dx"); \

Yes, that would work too, but I don't like forcing the asm to use
particular registers when there's no good reason to do so.

>
>
> PS. I'm very curious about how could you find this bug.

It was mainly down to the differences between the i386 and x86_64
versions, and trying to understand the reasons for those differences,
and indeed how the entire set of macros worked at all.

Paul

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