[PATCH v3 3/5] asm-generic: barrier: Add smp_cond_load_acquire_timewait()

[Ankur Arora]

Add the acquire variant of smp_cond_load_relaxed_timewait(). This
reuses the relaxed variant, with an additional LOAD->LOAD
ordering via smp_acquire__after_ctrl_dep().

Also, the rqspinlock implementation has a locally cached copy of
this interface. Fixup the parameters used there.

Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: linux-arch@xxxxxxxxxxxxxxx
Signed-off-by: Ankur Arora <ankur.a.arora@xxxxxxxxxx>
---
 arch/arm64/include/asm/rqspinlock.h |  2 +-
 include/asm-generic/barrier.h       | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/rqspinlock.h b/arch/arm64/include/asm/rqspinlock.h
index 9ea0a74e5892..f1b6a428013e 100644
--- a/arch/arm64/include/asm/rqspinlock.h
+++ b/arch/arm64/include/asm/rqspinlock.h
@@ -86,7 +86,7 @@
 
 #endif
 
-#define res_smp_cond_load_acquire(v, c) smp_cond_load_acquire_timewait(v, c, 0, 1)
+#define res_smp_cond_load_acquire(v, c) smp_cond_load_acquire_timewait(v, c, 0ULL, 1ULL, 0)
 
 #include <asm-generic/rqspinlock.h>
 
diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h
index 8299c57d1110..dd7c9ca2dff3 100644
--- a/include/asm-generic/barrier.h
+++ b/include/asm-generic/barrier.h
@@ -388,6 +388,28 @@ static inline u64 ___smp_cond_spinwait(u64 now, u64 prev, u64 end,
 	(typeof(*ptr))_val;						\
 })
 
+/**
+ * smp_cond_load_acquire_timewait() - (Spin) wait for cond with ACQUIRE ordering
+ * until a timeout expires.
+ *
+ * Arguments: same as smp_cond_load_relaxed_timeout().
+ *
+ * Equivalent to using smp_cond_load_acquire() on the condition variable with
+ * a timeout.
+ */
+#ifndef smp_cond_load_acquire_timewait
+#define smp_cond_load_acquire_timewait(ptr, cond_expr,			\
+				       time_expr, time_end,		\
+				       slack) ({			\
+	__unqual_scalar_typeof(*ptr) _val;				\
+	_val = smp_cond_load_relaxed_timewait(ptr, cond_expr,		\
+					      time_expr, time_end,	\
+					      slack);			\
+	/* Depends on the control dependency of the wait above. */	\
+	smp_acquire__after_ctrl_dep();					\
+	(typeof(*ptr))_val;						\
+})
+#endif
 /*
  * pmem_wmb() ensures that all stores for which the modification
  * are written to persistent storage by preceding instructions have
-- 
2.43.5