[PATCH] alpha: spinlock: don't perform memory access in locked critical section

Will Deacon
2013-05-06T20:01:27Z

The Alpha Architecture Reference Manual states that any memory access
performed between an LD_xL and a STx_C instruction may cause the
store-conditional to fail unconditionally and, as such, `no useful
program should do this'.

Linux is a useful program, so fix up the Alpha spinlock implementation
to use logical operations rather than load-address instructions for
generating immediates.

Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
arch/alpha/include/asm/spinlock.h | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/alpha/include/asm/spinlock.h b/arch/alpha/include/asm/spinlock.h
index 3bba21e..0c357cd 100644
--- a/arch/alpha/include/asm/spinlock.h
+++ b/arch/alpha/include/asm/spinlock.h
@@ -29,7 +29,7 @@ static inline void arch_spin_lock(arch_spinlock_t * lock)
__asm__ __volatile__(
"1: ldl_l %0,%1\n"
" bne %0,2f\n"
- " lda %0,1\n"
+ " mov 1,%0\n"
" stl_c %0,%1\n"
" beq %0,2f\n"
" mb\n"
@@ -86,7 +86,7 @@ static inline void arch_write_lock(arch_rwlock_t *lock)
__asm__ __volatile__(
"1: ldl_l %1,%0\n"
" bne %1,6f\n"
- " lda %1,1\n"
+ " mov 1,%1\n"
" stl_c %1,%0\n"
" beq %1,6f\n"
" mb\n"
@@ -106,7 +106,7 @@ static inline int arch_read_trylock(arch_rwlock_t * lock)

__asm__ __volatile__(
"1: ldl_l %1,%0\n"
- " lda %2,0\n"
+ " mov 0,%2\n"
" blbs %1,2f\n"
" subl %1,2,%2\n"
" stl_c %2,%0\n"
@@ -128,9 +128,9 @@ static inline int arch_write_trylock(arch_rwlock_t * lock)

__asm__ __volatile__(
"1: ldl_l %1,%0\n"
- " lda %2,0\n"
+ " mov 0,%2\n"
" bne %1,2f\n"
- " lda %2,1\n"
+ " mov 1,%2\n"
" stl_c %2,%0\n"
" beq %2,6f\n"
"2: mb\n"
--
1.8.2.2