Hi David,
On Wed, May 31, 2017 at 09:28:36AM -0700, David Daney wrote:
> On 05/31/2017 08:19 AM, James Hogan wrote:
> > Adjust the atomic loop in the MIPS_ATOMIC_SET operation of the sysmips
> > system call to branch straight back to the linked load rather than
> > jumping via a different subsection (whose purpose remains a mystery to
> > me).
>
> The subsection keeps the code for the (hopefully) cold path out of line
> which should result in a smaller cache footprint in the hot path.
Hmm, yes that would make sense if it did something useful there, but it
just immediately jumps back to the ll.
Cheers
James
>
>
> >
> > Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
> > Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
> > Cc: linux-mips@xxxxxxxxxxxxxx
> > ---
> > arch/mips/kernel/syscall.c | 6 +-----
> > 1 file changed, 1 insertion(+), 5 deletions(-)
> >
> > diff --git a/arch/mips/kernel/syscall.c b/arch/mips/kernel/syscall.c
> > index ca54ac40252b..6c6bf43d681b 100644
> > --- a/arch/mips/kernel/syscall.c
> > +++ b/arch/mips/kernel/syscall.c
> > @@ -137,13 +137,9 @@ static inline int mips_atomic_set(unsigned long addr, unsigned long new)
> > " move %[tmp], %[new] \n"
> > "2: \n"
> > user_sc("%[tmp]", "(%[addr])")
> > - " beqz %[tmp], 4f \n"
> > + " beqz %[tmp], 1b \n"
> > "3: \n"
> > " .insn \n"
> > - " .subsection 2 \n"
> > - "4: b 1b \n"
> > - " .previous \n"
> > - " \n"
> > " .section .fixup,\"ax\" \n"
> > "5: li %[err], %[efault] \n"
> > " j 3b \n"
> >
>
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