From a0307b90e502a48cc73ca936bce0792f5566ba64 Mon Sep 17 00:00:00 2001
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Wed, 22 Jun 2016 12:32:34 -0400
Subject: [PATCH] Fix: use clock_get_time for caa_get_cycles fallback on MacOSX

Use clock_get_time as fallback to read time for caa_get_cycles on
MacOSX. It should not matter much in practice, since x86 uses the cycle
counter.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
 configure.ac        |  7 ++++---
 urcu/arch/generic.h | 34 ++++++++++++++++++++++++++++++++++
 urcu/config.h.in    |  3 +++
 3 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/configure.ac b/configure.ac
index b3096c6..cf9964b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -25,6 +25,7 @@ AH_TEMPLATE([CONFIG_RCU_HAVE_FUTEX], [Defined when on a system with futex suppor
 AH_TEMPLATE([CONFIG_RCU_COMPAT_ARCH], [Compatibility mode for i386 which lacks cmpxchg instruction.])
 AH_TEMPLATE([CONFIG_RCU_ARM_HAVE_DMB], [Use the dmb instruction if available for use on ARM.])
 AH_TEMPLATE([CONFIG_RCU_TLS], [TLS provided by the compiler.])
+AH_TEMPLATE([CONFIG_RCU_HAVE_CLOCK_GETTIME], [clock_gettime() is detected.])
 
 # Allow overriding storage used for TLS variables.
 AC_ARG_ENABLE([compiler-tls],
@@ -221,9 +222,9 @@ AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
 ])
 
 # Search for clock_gettime
-AC_SEARCH_LIBS([clock_gettime], [rt], [],
-	[AC_MSG_ERROR([Cannot find clock_gettime function.])]
-)
+AC_SEARCH_LIBS([clock_gettime], [rt], [
+	AC_DEFINE([CONFIG_RCU_HAVE_CLOCK_GETTIME], [1])
+], [])
 
 # Check for pthread
 AC_CHECK_LIB([pthread], [pthread_create],
diff --git a/urcu/arch/generic.h b/urcu/arch/generic.h
index d423595..4b56ed7 100644
--- a/urcu/arch/generic.h
+++ b/urcu/arch/generic.h
@@ -153,6 +153,8 @@ extern "C" {
 #ifndef HAS_CAA_GET_CYCLES
 #define HAS_CAA_GET_CYCLES
 
+#ifdef CONFIG_RCU_HAVE_CLOCK_GETTIME
+
 #include <time.h>
 #include <stdint.h>
 
@@ -166,6 +168,38 @@ static inline caa_cycles_t caa_get_cycles (void)
 		return -1ULL;
 	return ((uint64_t) ts.tv_sec * 1000000000ULL) + ts.tv_nsec;
 }
+
+#elif defined(__APPLE__)
+
+#include <mach/mach.h>
+#include <mach/clock.h>
+#include <mach/mach_time.h>
+#include <time.h>
+#include <stdint.h>
+
+typedef uint64_t caa_cycles_t;
+
+static inline caa_cycles_t caa_get_cycles (void)
+{
+	mach_timespec_t ts = { 0, 0 };
+	static clock_serv_t clock_service;
+
+	if (caa_unlikely(!clock_service)) {
+		if (host_get_clock_service(mach_host_self(),
+				SYSTEM_CLOCK, &clock_service))
+			return -1ULL;
+	}
+	if (caa_unlikely(clock_get_time(clock_service, &ts)))
+		return -1ULL;
+	return ((uint64_t) ts.tv_sec * 1000000000ULL) + ts.tv_nsec;
+}
+
+#else
+
+#error caa_get_cycles() not implemented for this platform.
+
+#endif
+
 #endif /* HAS_CAA_GET_CYCLES */
 
 #ifdef __cplusplus
diff --git a/urcu/config.h.in b/urcu/config.h.in
index 98ea365..4b856dc 100644
--- a/urcu/config.h.in
+++ b/urcu/config.h.in
@@ -19,3 +19,6 @@
 
 /* TLS provided by the compiler. */
 #undef CONFIG_RCU_TLS
+
+/* clock_gettime() is detected. */
+#undef CONFIG_RCU_HAVE_CLOCK_GETTIME
-- 
2.34.1