thread/primitive: add platform wrappers for pause/yield instructions

CMakeLists.txt

@@ -157,8 +157,9 @@ endif ()
 ###############################################################################
 list (APPEND UTIL_FILES
     thread/event.hpp
-    thread/semaphore.hpp
     thread/flag.hpp
+    thread/primitive.hpp
+    thread/semaphore.hpp
 )
 
 if (LINUX)

parallel/queue.hpp

@@ -3,13 +3,13 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  *
- * Copyright 2018 Danny Robson <danny@nerdcruft.net>
+ * Copyright 2018-2019 Danny Robson <danny@nerdcruft.net>
  */
 
-#ifndef CRUFT_UTIL_PARALLEL_QUEUE_HPP
-#define CRUFT_UTIL_PARALLEL_QUEUE_HPP
+#pragma once
 
 #include "../maths.hpp"
+#include "../thread/primitive.hpp"
 
 #include <atomic>
 #include <type_traits>
@@ -78,7 +78,7 @@ namespace cruft::parallel {
 
                 // try to bump the write cursor to claim that slot
                 if (uint32_t orig = curr; !m_write.compare_exchange_weak (orig, next)) {
-                    asm volatile ("pause;");
+                    pause ();
                     continue;
                 }
 
@@ -92,7 +92,7 @@ namespace cruft::parallel {
                     uint32_t orig = curr;
                     if (m_read.hi.compare_exchange_weak (orig, next))
                         break;
-                    asm volatile ("pause;");
+                    pause ();
                 } while (1);
 
                 return true;
@@ -132,7 +132,7 @@ namespace cruft::parallel {
                 if (uint32_t orig = curr; m_read.lo.compare_exchange_weak (orig, next))
                     return true;
 
-                asm volatile ("pause;");
+                pause ();
             } while (1);
         }
 
@@ -156,5 +156,3 @@ namespace cruft::parallel {
         } m_read;
     };
 }
-
-#endif

thread/primitive.hpp

@@ -0,0 +1,25 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * Copyright 2019 Danny Robson <danny@nerdcruft.net>
+ */
+
+#pragma once
+
+#include "../platform.hpp"
+
+
+namespace cruft {
+    inline void pause [[gnu::always_inline]] (void)
+    {
+        #ifdef PROCESSOR_AMD64
+        asm volatile ("pause");
+        #elif PROCESSOR_ARM
+        asm volatile ("yield");
+        #else
+        #error "Unhandled processor type"
+        #endif
+    }
+}

thread/spinlock.cpp

@@ -3,11 +3,13 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  *
- * Copyright 2018 Danny Robson <danny@nerdcruft.net>
+ * Copyright 2018-2019 Danny Robson <danny@nerdcruft.net>
  */
 
 #include "spinlock.hpp"
 
+#include "primitive.hpp"
+
 #include "../debug.hpp"
 
 using cruft::thread::spinlock;
@@ -35,7 +37,7 @@ spinlock::lock (void)
             return;
 
         while (held)
-            __asm__ volatile ("pause");
+            pause ();
     } while (true);
 }
 

thread/ticketlock.cpp

@@ -3,10 +3,11 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  *
- * Copyright 2018 Danny Robson <danny@nerdcruft.net>
+ * Copyright 2018-2019 Danny Robson <danny@nerdcruft.net>
  */
 
 #include "ticketlock.hpp"
+#include "primitive.hpp"
 
 using cruft::thread::ticketlock;
 
@@ -25,7 +26,7 @@ ticketlock::lock (void)
     auto self = next++;
 
     while (current != self)
-        __asm__ volatile ("pause");
+        pause ();
 }