Use process-local futex operations

The FUTEX_WAIT and FUTEX_WAKE operations are supposed to be applied to futexes that can be shared between processes. Using process-local equivalents can be more efficient.

Also add linux/futex.h include, which should nowdays be provided by all relevant Linux distributions. Since linux_common.h is also included on various BSD systems, include sys/futex.h where available and disable futex API where not.

include/tbb/machine/linux_common.h

@@ -31,18 +31,39 @@
 
 #if defined(SYS_futex)
 
+/*
+ * Note that this header is included not only on Linux. Some BSD systems may also support futexes,
+ * but provide the definitions in other headers.
+ */
+#if defined(__linux__)
+#include <linux/futex.h>
+#define __TBB_USE_FUTEX 1
+#elif defined(__OpenBSD__)
+#include <sys/futex.h>
 #define __TBB_USE_FUTEX 1
+#elif defined(__has_include)
+#if __has_include(<sys/futex.h>)
+#include <sys/futex.h>
+#define __TBB_USE_FUTEX 1
+#endif
+#endif
+
+#if __TBB_USE_FUTEX
+
 #include <limits.h>
 #include <errno.h>
-// Unfortunately, some versions of Linux do not have a header that defines FUTEX_WAIT and FUTEX_WAKE.
 
-#ifdef FUTEX_WAIT
+#if defined(FUTEX_WAIT_PRIVATE)
+#define __TBB_FUTEX_WAIT FUTEX_WAIT_PRIVATE
+#elif defined(FUTEX_WAIT)
 #define __TBB_FUTEX_WAIT FUTEX_WAIT
 #else
 #define __TBB_FUTEX_WAIT 0
 #endif
 
-#ifdef FUTEX_WAKE
+#if defined(FUTEX_WAKE_PRIVATE)
+#define __TBB_FUTEX_WAKE FUTEX_WAKE_PRIVATE
+#elif defined(FUTEX_WAKE)
 #define __TBB_FUTEX_WAKE FUTEX_WAKE
 #else
 #define __TBB_FUTEX_WAKE 1
@@ -81,4 +102,6 @@ inline int futex_wakeup_all( void *futex ) {
 
 } /* namespace tbb */
 
+#endif /* __TBB_USE_FUTEX */
+
 #endif /* SYS_futex */

include/tbb/tbb_machine.h

@@ -227,7 +227,7 @@ template<> struct atomic_selector<8> {
         #include "machine/linux_intel64.h"
     #endif
 
-#elif __linux__ || __FreeBSD__ || __NetBSD__
+#elif __linux__ || __FreeBSD__ || __NetBSD__ || __OpenBSD__
 
     #if (TBB_USE_GCC_BUILTINS && __TBB_GCC_BUILTIN_ATOMICS_PRESENT)
         #include "machine/gcc_generic.h"