On 05/31/2017 09:47 AM, James Hogan wrote:
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.
In this case, it could be that the pattern was copied without carefully
examining what was being done.
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"
