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-rw-r--r--arch/arc/include/asm/spinlock.h32
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();
}