diff options
Diffstat (limited to 'arch/arc/include/asm/spinlock.h')
| -rw-r--r-- | arch/arc/include/asm/spinlock.h | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/arch/arc/include/asm/spinlock.h b/arch/arc/include/asm/spinlock.h index b6a8c2dfbe6e..e1651df6a93d 100644 --- a/arch/arc/include/asm/spinlock.h +++ b/arch/arc/include/asm/spinlock.h @@ -22,24 +22,46 @@ static inline void arch_spin_lock(arch_spinlock_t *lock) { unsigned int tmp = __ARCH_SPIN_LOCK_LOCKED__; + /* + * This smp_mb() is technically superfluous, we only need the one + * after the lock for providing the ACQUIRE semantics. + * However doing the "right" thing was regressing hackbench + * so keeping this, pending further investigation + */ + smp_mb(); + __asm__ __volatile__( "1: ex %0, [%1] \n" " breq %0, %2, 1b \n" : "+&r" (tmp) : "r"(&(lock->slock)), "ir"(__ARCH_SPIN_LOCK_LOCKED__) : "memory"); + + /* + * ACQUIRE barrier to ensure load/store after taking the lock + * don't "bleed-up" out of the critical section (leak-in is allowed) + * http://www.spinics.net/lists/kernel/msg2010409.html + * + * ARCv2 only has load-load, store-store and all-all barrier + * thus need the full all-all barrier + */ + smp_mb(); } static inline int arch_spin_trylock(arch_spinlock_t *lock) { unsigned int tmp = __ARCH_SPIN_LOCK_LOCKED__; + smp_mb(); + __asm__ __volatile__( "1: ex %0, [%1] \n" : "+r" (tmp) : "r"(&(lock->slock)) : "memory"); + smp_mb(); + return (tmp == __ARCH_SPIN_LOCK_UNLOCKED__); } @@ -47,12 +69,22 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock) { unsigned int tmp = __ARCH_SPIN_LOCK_UNLOCKED__; + /* + * RELEASE barrier: given the instructions avail on ARCv2, full barrier + * is the only option + */ + smp_mb(); + __asm__ __volatile__( " ex %0, [%1] \n" : "+r" (tmp) : "r"(&(lock->slock)) : "memory"); + /* + * superfluous, but keeping for now - see pairing version in + * arch_spin_lock above + */ smp_mb(); } |