ARM: locks: prefetch the destination word for write prior to strex

[~andy/linux] / arch / arm / include / asm / spinlock.h

diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h
index e1ce4523091315590b75e1beed55076931c94eb0..499900781d59fe21e07c5f574858ae4bfc4aaaa9 100644 (file)
--- a/arch/arm/include/asm/spinlock.h
+++ b/arch/arm/include/asm/spinlock.h
@@ -5,7 +5,7 @@
 #error SMP not supported on pre-ARMv6 CPUs
 #endif
 
-#include <asm/processor.h>
+#include <linux/prefetch.h>
 
 /*
  * sev and wfe are ARMv6K extensions.  Uniprocessor ARMv6 may not have the K
@@ -70,6 +70,7 @@ static inline void arch_spin_lock(arch_spinlock_t *lock)
        u32 newval;
        arch_spinlock_t lockval;
 
+       prefetchw(&lock->slock);
        __asm__ __volatile__(
 "1:    ldrex   %0, [%3]\n"
 "      add     %1, %0, %4\n"
@@ -93,6 +94,7 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock)
        unsigned long contended, res;
        u32 slock;
 
+       prefetchw(&lock->slock);
        do {
                __asm__ __volatile__(
                "       ldrex   %0, [%3]\n"
@@ -145,6 +147,7 @@ static inline void arch_write_lock(arch_rwlock_t *rw)
 {
        unsigned long tmp;
 
+       prefetchw(&rw->lock);
        __asm__ __volatile__(
 "1:    ldrex   %0, [%1]\n"
 "      teq     %0, #0\n"
@@ -163,6 +166,7 @@ static inline int arch_write_trylock(arch_rwlock_t *rw)
 {
        unsigned long contended, res;
 
+       prefetchw(&rw->lock);
        do {
                __asm__ __volatile__(
                "       ldrex   %0, [%2]\n"
@@ -196,7 +200,7 @@ static inline void arch_write_unlock(arch_rwlock_t *rw)
 }
 
 /* write_can_lock - would write_trylock() succeed? */
-#define arch_write_can_lock(x)         ((x)->lock == 0)
+#define arch_write_can_lock(x)         (ACCESS_ONCE((x)->lock) == 0)
 
 /*
  * Read locks are a bit more hairy:
@@ -214,6 +218,7 @@ static inline void arch_read_lock(arch_rwlock_t *rw)
 {
        unsigned long tmp, tmp2;
 
+       prefetchw(&rw->lock);
        __asm__ __volatile__(
 "1:    ldrex   %0, [%2]\n"
 "      adds    %0, %0, #1\n"
@@ -234,6 +239,7 @@ static inline void arch_read_unlock(arch_rwlock_t *rw)
 
        smp_mb();
 
+       prefetchw(&rw->lock);
        __asm__ __volatile__(
 "1:    ldrex   %0, [%2]\n"
 "      sub     %0, %0, #1\n"
@@ -252,6 +258,7 @@ static inline int arch_read_trylock(arch_rwlock_t *rw)
 {
        unsigned long contended, res;
 
+       prefetchw(&rw->lock);
        do {
                __asm__ __volatile__(
                "       ldrex   %0, [%2]\n"
@@ -273,7 +280,7 @@ static inline int arch_read_trylock(arch_rwlock_t *rw)
 }
 
 /* read_can_lock - would read_trylock() succeed? */
-#define arch_read_can_lock(x)          ((x)->lock < 0x80000000)
+#define arch_read_can_lock(x)          (ACCESS_ONCE((x)->lock) < 0x80000000)
 
 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)