diff options
Diffstat (limited to 'arch/arc/include/asm/cmpxchg.h')
| -rw-r--r-- | arch/arc/include/asm/cmpxchg.h | 26 |
1 files changed, 22 insertions, 4 deletions
diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h index 03cd6894855d..44fd531f4d7b 100644 --- a/arch/arc/include/asm/cmpxchg.h +++ b/arch/arc/include/asm/cmpxchg.h @@ -10,6 +10,8 @@ #define __ASM_ARC_CMPXCHG_H #include <linux/types.h> + +#include <asm/barrier.h> #include <asm/smp.h> #ifdef CONFIG_ARC_HAS_LLSC @@ -19,16 +21,25 @@ __cmpxchg(volatile void *ptr, unsigned long expected, unsigned long new) { unsigned long prev; + /* + * Explicit full memory barrier needed before/after as + * LLOCK/SCOND thmeselves don't provide any such semantics + */ + smp_mb(); + __asm__ __volatile__( "1: llock %0, [%1] \n" " brne %0, %2, 2f \n" " scond %3, [%1] \n" " bnz 1b \n" "2: \n" - : "=&r"(prev) - : "r"(ptr), "ir"(expected), - "r"(new) /* can't be "ir". scond can't take limm for "b" */ - : "cc"); + : "=&r"(prev) /* Early clobber, to prevent reg reuse */ + : "r"(ptr), /* Not "m": llock only supports reg direct addr mode */ + "ir"(expected), + "r"(new) /* can't be "ir". scond can't take LIMM for "b" */ + : "cc", "memory"); /* so that gcc knows memory is being written here */ + + smp_mb(); return prev; } @@ -42,6 +53,9 @@ __cmpxchg(volatile void *ptr, unsigned long expected, unsigned long new) int prev; volatile unsigned long *p = ptr; + /* + * spin lock/unlock provide the needed smp_mb() before/after + */ atomic_ops_lock(flags); prev = *p; if (prev == expected) @@ -77,12 +91,16 @@ static inline unsigned long __xchg(unsigned long val, volatile void *ptr, switch (size) { case 4: + smp_mb(); + __asm__ __volatile__( " ex %0, [%1] \n" : "+r"(val) : "r"(ptr) : "memory"); + smp_mb(); + return val; } return __xchg_bad_pointer(); |