From: Joshua Kinard <kumba@xxxxxxxxxx>
This patch reduces down the conditionals in MIPS atomic code that
deal with a silicon bug in early R10000 cpus that required a workaround
of a branch-likely instruction following a store-conditional in order
to guarantee the whole ll/sc sequence is atomic. As the only real
difference is a branch-likely instruction (beqzl) over a standard
branch (beqz), the conditional is reduced down to down to a single
preprocessor check at the top to pick the required instruction.
This requires writing the uses in assembler, thus we discard the
non-R10000 case that uses a mixture of a C do...while loop with
embedded assembler that was added back in commit 7837314d141c, while
also addressing a note found in the git log for empty commit
5999eca25c1f.
The macro definition for the branch instruction and the code comment
derives from a patch sent in earlier by Paul Burton for various cmpxchg
cleanups.
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: Paul Burton <paul.burton@xxxxxxxxxx>
Signed-off-by: Joshua Kinard <kumba@xxxxxxxxxx>
---
arch/mips/include/asm/atomic.h | 187 +++++--------------------------
1 file changed, 35 insertions(+), 152 deletions(-)
diff --git a/arch/mips/include/asm/atomic.h b/arch/mips/include/asm/atomic.h
index 0ab176bdb8e8..404e64e57a72 100644
--- a/arch/mips/include/asm/atomic.h
+++ b/arch/mips/include/asm/atomic.h
@@ -22,6 +22,17 @@
#include <asm/cmpxchg.h>
#include <asm/war.h>
+/*
+ * Using a branch-likely instruction to check the result of an sc instruction
+ * works around a bug present in R10000 CPUs prior to revision 3.0 that could
+ * cause ll-sc sequences to execute non-atomically.
+ */
+#if R10000_LLSC_WAR
+# define __scbeqz "beqzl"
+#else
+# define __scbeqz "beqz"
+#endif
+
#define ATOMIC_INIT(i) { (i) }
/*
@@ -44,31 +55,18 @@
#define ATOMIC_OP(op, c_op, asm_op) \
static __inline__ void atomic_##op(int i, atomic_t * v) \
{ \
- if (kernel_uses_llsc && R10000_LLSC_WAR) { \
+ if (kernel_uses_llsc) { \
int temp; \
\
__asm__ __volatile__( \
- " .set arch=r4000 \n" \
+ " .set "MIPS_ISA_LEVEL" \n" \
"1: ll %0, %1 # atomic_" #op " \n" \
" " #asm_op " %0, %2 \n" \
" sc %0, %1 \n" \
- " beqzl %0, 1b \n" \
+ "\t" __scbeqz " %0, 1b \n" \
" .set mips0 \n" \
: "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (v->counter) \
: "Ir" (i)); \
- } else if (kernel_uses_llsc) { \
- int temp; \
- \
- do { \
- __asm__ __volatile__( \
- " .set "MIPS_ISA_LEVEL" \n" \
- " ll %0, %1 # atomic_" #op "\n" \
- " " #asm_op " %0, %2 \n" \
- " sc %0, %1 \n" \
- " .set mips0 \n" \
- : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (v->counter) \
- : "Ir" (i)); \
- } while (unlikely(!temp)); \
} else { \
unsigned long flags; \
\
@@ -83,36 +81,20 @@ static __inline__ int atomic_##op##_return_relaxed(int i, atomic_t * v) \
{ \
int result; \
\
- if (kernel_uses_llsc && R10000_LLSC_WAR) { \
+ if (kernel_uses_llsc) { \
int temp; \
\
__asm__ __volatile__( \
- " .set arch=r4000 \n" \
+ " .set "MIPS_ISA_LEVEL" \n" \
"1: ll %1, %2 # atomic_" #op "_return \n" \
" " #asm_op " %0, %1, %3 \n" \
" sc %0, %2 \n" \
- " beqzl %0, 1b \n" \
+ "\t" __scbeqz " %0, 1b \n" \
" " #asm_op " %0, %1, %3 \n" \
" .set mips0 \n" \
: "=&r" (result), "=&r" (temp), \
"+" GCC_OFF_SMALL_ASM() (v->counter) \
: "Ir" (i)); \
- } else if (kernel_uses_llsc) { \
- int temp; \
- \
- do { \
- __asm__ __volatile__( \
- " .set "MIPS_ISA_LEVEL" \n" \
- " ll %1, %2 # atomic_" #op "_return \n" \
- " " #asm_op " %0, %1, %3 \n" \
- " sc %0, %2 \n" \
- " .set mips0 \n" \
- : "=&r" (result), "=&r" (temp), \
- "+" GCC_OFF_SMALL_ASM() (v->counter) \
- : "Ir" (i)); \
- } while (unlikely(!result)); \
- \
- result = temp; result c_op i; \
} else { \
unsigned long flags; \
\
@@ -131,36 +113,20 @@ static __inline__ int atomic_fetch_##op##_relaxed(int i, atomic_t * v) \
{ \
int result; \
\
- if (kernel_uses_llsc && R10000_LLSC_WAR) { \
+ if (kernel_uses_llsc) { \
int temp; \
\
__asm__ __volatile__( \
- " .set arch=r4000 \n" \
+ " .set "MIPS_ISA_LEVEL" \n" \
"1: ll %1, %2 # atomic_fetch_" #op " \n" \
" " #asm_op " %0, %1, %3 \n" \
" sc %0, %2 \n" \
- " beqzl %0, 1b \n" \
+ "\t" __scbeqz " %0, 1b \n" \
" move %0, %1 \n" \
" .set mips0 \n" \
: "=&r" (result), "=&r" (temp), \
"+" GCC_OFF_SMALL_ASM() (v->counter) \
: "Ir" (i)); \
- } else if (kernel_uses_llsc) { \
- int temp; \
- \
- do { \
- __asm__ __volatile__( \
- " .set "MIPS_ISA_LEVEL" \n" \
- " ll %1, %2 # atomic_fetch_" #op " \n" \
- " " #asm_op " %0, %1, %3 \n" \
- " sc %0, %2 \n" \
- " .set mips0 \n" \
- : "=&r" (result), "=&r" (temp), \
- "+" GCC_OFF_SMALL_ASM() (v->counter) \
- : "Ir" (i)); \
- } while (unlikely(!result)); \
- \
- result = temp; \
} else { \
unsigned long flags; \
\
@@ -218,17 +184,17 @@ static __inline__ int atomic_sub_if_positive(int i, atomic_t * v)
smp_mb__before_llsc();
- if (kernel_uses_llsc && R10000_LLSC_WAR) {
+ if (kernel_uses_llsc) {
int temp;
__asm__ __volatile__(
- " .set arch=r4000 \n"
+ " .set "MIPS_ISA_LEVEL" \n"
"1: ll %1, %2 # atomic_sub_if_positive\n"
" subu %0, %1, %3 \n"
" bltz %0, 1f \n"
" sc %0, %2 \n"
" .set noreorder \n"
- " beqzl %0, 1b \n"
+ "\t" __scbeqz " %0, 1b \n"
" subu %0, %1, %3 \n"
" .set reorder \n"
"1: \n"
@@ -237,24 +203,6 @@ static __inline__ int atomic_sub_if_positive(int i, atomic_t * v)
"+" GCC_OFF_SMALL_ASM() (v->counter)
: "Ir" (i), GCC_OFF_SMALL_ASM() (v->counter)
: "memory");
- } else if (kernel_uses_llsc) {
- int temp;
-
- __asm__ __volatile__(
- " .set "MIPS_ISA_LEVEL" \n"
- "1: ll %1, %2 # atomic_sub_if_positive\n"
- " subu %0, %1, %3 \n"
- " bltz %0, 1f \n"
- " sc %0, %2 \n"
- " .set noreorder \n"
- " beqz %0, 1b \n"
- " subu %0, %1, %3 \n"
- " .set reorder \n"
- "1: \n"
- " .set mips0 \n"
- : "=&r" (result), "=&r" (temp),
- "+" GCC_OFF_SMALL_ASM() (v->counter)
- : "Ir" (i));
} else {
unsigned long flags;
@@ -386,31 +334,18 @@ static __inline__ int __atomic_add_unless(atomic_t *v, int a, int u)
#define ATOMIC64_OP(op, c_op, asm_op) \
static __inline__ void atomic64_##op(long i, atomic64_t * v) \
{ \
- if (kernel_uses_llsc && R10000_LLSC_WAR) { \
+ if (kernel_uses_llsc) { \
long temp; \
\
__asm__ __volatile__( \
- " .set arch=r4000 \n" \
+ " .set "MIPS_ISA_LEVEL" \n" \
"1: lld %0, %1 # atomic64_" #op " \n" \
" " #asm_op " %0, %2 \n" \
" scd %0, %1 \n" \
- " beqzl %0, 1b \n" \
+ "\t" __scbeqz " %0, 1b \n" \
" .set mips0 \n" \
: "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (v->counter) \
: "Ir" (i)); \
- } else if (kernel_uses_llsc) { \
- long temp; \
- \
- do { \
- __asm__ __volatile__( \
- " .set "MIPS_ISA_LEVEL" \n" \
- " lld %0, %1 # atomic64_" #op "\n" \
- " " #asm_op " %0, %2 \n" \
- " scd %0, %1 \n" \
- " .set mips0 \n" \
- : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (v->counter) \
- : "Ir" (i)); \
- } while (unlikely(!temp)); \
} else { \
unsigned long flags; \
\
@@ -425,37 +360,20 @@ static __inline__ long atomic64_##op##_return_relaxed(long i, atomic64_t * v) \
{ \
long result; \
\
- if (kernel_uses_llsc && R10000_LLSC_WAR) { \
+ if (kernel_uses_llsc) { \
long temp; \
\
__asm__ __volatile__( \
- " .set arch=r4000 \n" \
+ " .set "MIPS_ISA_LEVEL" \n" \
"1: lld %1, %2 # atomic64_" #op "_return\n" \
" " #asm_op " %0, %1, %3 \n" \
" scd %0, %2 \n" \
- " beqzl %0, 1b \n" \
+ "\t" __scbeqz " %0, 1b \n" \
" " #asm_op " %0, %1, %3 \n" \
" .set mips0 \n" \
: "=&r" (result), "=&r" (temp), \
"+" GCC_OFF_SMALL_ASM() (v->counter) \
: "Ir" (i)); \
- } else if (kernel_uses_llsc) { \
- long temp; \
- \
- do { \
- __asm__ __volatile__( \
- " .set "MIPS_ISA_LEVEL" \n" \
- " lld %1, %2 # atomic64_" #op "_return\n" \
- " " #asm_op " %0, %1, %3 \n" \
- " scd %0, %2 \n" \
- " .set mips0 \n" \
- : "=&r" (result), "=&r" (temp), \
- "=" GCC_OFF_SMALL_ASM() (v->counter) \
- : "Ir" (i), GCC_OFF_SMALL_ASM() (v->counter) \
- : "memory"); \
- } while (unlikely(!result)); \
- \
- result = temp; result c_op i; \
} else { \
unsigned long flags; \
\
@@ -474,37 +392,20 @@ static __inline__ long atomic64_fetch_##op##_relaxed(long i, atomic64_t * v) \
{ \
long result; \
\
- if (kernel_uses_llsc && R10000_LLSC_WAR) { \
+ if (kernel_uses_llsc) { \
long temp; \
\
__asm__ __volatile__( \
- " .set arch=r4000 \n" \
+ " .set "MIPS_ISA_LEVEL" \n" \
"1: lld %1, %2 # atomic64_fetch_" #op "\n" \
" " #asm_op " %0, %1, %3 \n" \
" scd %0, %2 \n" \
- " beqzl %0, 1b \n" \
+ "\t" __scbeqz " %0, 1b \n" \
" move %0, %1 \n" \
" .set mips0 \n" \
: "=&r" (result), "=&r" (temp), \
"+" GCC_OFF_SMALL_ASM() (v->counter) \
: "Ir" (i)); \
- } else if (kernel_uses_llsc) { \
- long temp; \
- \
- do { \
- __asm__ __volatile__( \
- " .set "MIPS_ISA_LEVEL" \n" \
- " lld %1, %2 # atomic64_fetch_" #op "\n" \
- " " #asm_op " %0, %1, %3 \n" \
- " scd %0, %2 \n" \
- " .set mips0 \n" \
- : "=&r" (result), "=&r" (temp), \
- "=" GCC_OFF_SMALL_ASM() (v->counter) \
- : "Ir" (i), GCC_OFF_SMALL_ASM() (v->counter) \
- : "memory"); \
- } while (unlikely(!result)); \
- \
- result = temp; \
} else { \
unsigned long flags; \
\
@@ -563,17 +464,17 @@ static __inline__ long atomic64_sub_if_positive(long i, atomic64_t * v)
smp_mb__before_llsc();
- if (kernel_uses_llsc && R10000_LLSC_WAR) {
+ if (kernel_uses_llsc) {
long temp;
__asm__ __volatile__(
- " .set arch=r4000 \n"
+ " .set "MIPS_ISA_LEVEL" \n"
"1: lld %1, %2 # atomic64_sub_if_positive\n"
" dsubu %0, %1, %3 \n"
" bltz %0, 1f \n"
" scd %0, %2 \n"
" .set noreorder \n"
- " beqzl %0, 1b \n"
+ "\t" __scbeqz " %0, 1b \n"
" dsubu %0, %1, %3 \n"
" .set reorder \n"
"1: \n"
@@ -582,24 +483,6 @@ static __inline__ long atomic64_sub_if_positive(long i, atomic64_t * v)
"=" GCC_OFF_SMALL_ASM() (v->counter)
: "Ir" (i), GCC_OFF_SMALL_ASM() (v->counter)
: "memory");
- } else if (kernel_uses_llsc) {
- long temp;
-
- __asm__ __volatile__(
- " .set "MIPS_ISA_LEVEL" \n"
- "1: lld %1, %2 # atomic64_sub_if_positive\n"
- " dsubu %0, %1, %3 \n"
- " bltz %0, 1f \n"
- " scd %0, %2 \n"
- " .set noreorder \n"
- " beqz %0, 1b \n"
- " dsubu %0, %1, %3 \n"
- " .set reorder \n"
- "1: \n"
- " .set mips0 \n"
- : "=&r" (result), "=&r" (temp),
- "+" GCC_OFF_SMALL_ASM() (v->counter)
- : "Ir" (i));
} else {
unsigned long flags;
