[PATCH v8 06/12] asm-generic: barrier: Add smp_cond_load_acquire_timeout()

[Ankur Arora]

Add the acquire variant of smp_cond_load_relaxed_timeout(). This
reuses the relaxed variant, with additional LOAD->LOAD ordering.

Cc: Arnd Bergmann <arnd at arndb.de>
Cc: Will Deacon <will at kernel.org>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: linux-arch at vger.kernel.org
Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>
Reviewed-by: Haris Okanovic <harisokn at amazon.com>
Tested-by: Haris Okanovic <harisokn at amazon.com>
Signed-off-by: Ankur Arora <ankur.a.arora at oracle.com>
---
 include/asm-generic/barrier.h | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h
index e25592f9fcbf..d05d34bece0d 100644
--- a/include/asm-generic/barrier.h
+++ b/include/asm-generic/barrier.h
@@ -331,6 +331,32 @@ __done:								\
 })
 #endif
 
+/**
+ * smp_cond_load_acquire_timeout() - (Spin) wait for cond with ACQUIRE ordering
+ * until a timeout expires.
+ * @ptr: pointer to the variable to wait on
+ * @cond: boolean expression to wait for
+ * @time_expr_ns: monotonic expression that evaluates to time in ns or,
+ *  on failure, returns a negative value.
+ * @timeout_ns: timeout value in ns
+ * (Both of the above are assumed to be compatible with s64.)
+ *
+ * Equivalent to using smp_cond_load_acquire() on the condition variable with
+ * a timeout.
+ */
+#ifndef smp_cond_load_acquire_timeout
+#define smp_cond_load_acquire_timeout(ptr, cond_expr,			\
+				      time_expr_ns, timeout_ns)		\
+({									\
+	__unqual_scalar_typeof(*ptr) _val;				\
+	_val = smp_cond_load_relaxed_timeout(ptr, cond_expr,		\
+					     time_expr_ns,		\
+					     timeout_ns);		\
+	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
-- 
2.31.1