[PATCH v4 6/6] powerpc: implement smp_cond_load_relaxed

[Nicholas Piggin]

This implements smp_cond_load_relaed with the slowpath busy loop using the
preferred SMT priority pattern.

Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
 arch/powerpc/include/asm/barrier.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/powerpc/include/asm/barrier.h 
b/arch/powerpc/include/asm/barrier.h
index 123adcefd40f..9b4671d38674 100644
--- a/arch/powerpc/include/asm/barrier.h
+++ b/arch/powerpc/include/asm/barrier.h
@@ -76,6 +76,20 @@ do {                                                         
        \
        ___p1;                                                          \
 })
 
+#define smp_cond_load_relaxed(ptr, cond_expr) ({               \
+       typeof(ptr) __PTR = (ptr);                              \
+       __unqual_scalar_typeof(*ptr) VAL;                       \
+       VAL = READ_ONCE(*__PTR);                                \
+       if (unlikely(!(cond_expr))) {                           \
+               spin_begin();                                   \
+               do {                                            \
+                       VAL = READ_ONCE(*__PTR);                \
+               } while (!(cond_expr));                         \
+               spin_end();                                     \
+       }                                                       \
+       (typeof(*ptr))VAL;                                      \
+})
+
 #ifdef CONFIG_PPC_BOOK3S_64
 #define NOSPEC_BARRIER_SLOT   nop
 #elif defined(CONFIG_PPC_FSL_BOOK3E)
-- 
2.23.0