[PATCH -v4 4/7] locking, tile: Provide TILE specific smp_acquire__after_ctrl_dep

[Peter Zijlstra]

Since TILE doesn't do read speculation, its control dependencies also
guarantee LOAD->LOAD order and we don't need the additional RMB
otherwise required to provide ACQUIRE semantics.

Acked-by: Chris Metcalf <cmetcalf@xxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 arch/tile/include/asm/barrier.h |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/arch/tile/include/asm/barrier.h
+++ b/arch/tile/include/asm/barrier.h
@@ -87,6 +87,13 @@ mb_incoherent(void)
 #define __smp_mb__after_atomic()	__smp_mb()
 #endif
 
+/*
+ * The TILE architecture does not do speculative reads; this ensures
+ * that a control dependency also orders against loads and already provides
+ * a LOAD->{LOAD,STORE} order and can forgo the additional RMB.
+ */
+#define smp_acquire__after_ctrl_dep()	barrier()
+
 #include <asm-generic/barrier.h>
 
 #endif /* !__ASSEMBLY__ */