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SubjectRE: [ACPI] ACPI global lock macros
On Thu, 11 Dec 2003, Yu, Luming wrote:
> -----Original Message-----
> From: acpi-devel-admin@lists.sourceforge.net [mailto:acpi-devel-admin@lists.sourceforge.net]On Behalf Of Yu, Luming
> Sent: 2003?12?11? 15:06
> To: Paul Menage; agrover@groveronline.com
> Cc: linux-kernel@vger.kernel.org; acpi-devel@lists.sourceforge.net
> Subject: RE: [ACPI] ACPI global lock macros
>
>
> >>#define ACPI_ACQUIRE_GLOBAL_LOCK(GLptr, Acq) \
> >> do { \
> >> asm volatile("1:movl (%1),%%eax;" \
> >> "movl %%eax,%%edx;" \
> >> "andl %2,%%edx;" \
> >> "btsl $0x1,%%edx;" \
> >> "adcl $0x0,%%edx;" \
> >> "lock; cmpxchgl %%edx,(%1);" \
> >> "jnz 1b;" \
> >> "cmpb $0x3,%%dl;" \
> >> "sbbl %0,%0" \
> >> :"=r"(Acq):"r"(GLptr),"i"(~1L):"dx", "ax"); \
> >> } while(0)
>
> 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 !
>
> 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"); \

FYI, that's what we do in FreeBSD also. The only difference after your
patch is that we use +m for GLptr.

#define ACPI_ACQUIRE_GLOBAL_LOCK(GLptr, Acq) \
do { \
asm("1: movl %1,%%eax;" \
"movl %%eax,%%edx;" \
"andl %2,%%edx;" \
"btsl $0x1,%%edx;" \
"adcl $0x0,%%edx;" \
"lock; cmpxchgl %%edx,%1;" \
"jnz 1b;" \
"cmpb $0x3,%%dl;" \
"sbbl %%eax,%%eax" \
: "=a" (Acq), "+m" (GLptr) : "i" (~1L) : "edx"); \
} while(0)

-Nate
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