From 34481768cbce0991bfba1d511dad81893a9004a9 Mon Sep 17 00:00:00 2001
From: Brad Hubbard <bhubbard@redhat.com>
Date: Thu, 30 Mar 2017 16:50:32 +1000
Subject: [PATCH] common: Make spinlock delay more conventional

The accepted method of implementing a spinlock delay is the "pause"
instruction.

Signed-off-by: Brad Hubbard <bhubbard@redhat.com>
---
 src/common/simple_spin.cc | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/common/simple_spin.cc b/src/common/simple_spin.cc
index fc4ac633deaf1..2d875365e0560 100644
--- a/src/common/simple_spin.cc
+++ b/src/common/simple_spin.cc
@@ -18,9 +18,6 @@
 #include <stdint.h>
 #include <pthread.h>
 
-static uint32_t bar = 13;
-static uint32_t *foo = &bar;
- 
 void simple_spin_lock(simple_spinlock_t *lock)
 {
   while(1) {
@@ -31,9 +28,15 @@ void simple_spin_lock(simple_spinlock_t *lock)
 	return;
     }
     // delay
-    for (int i = 0; i < 100000; i++) {
-      *foo = (*foo * 33) + 17;
-    }
+#if defined(__i386__) || defined(__x86_64__)
+    asm volatile("pause");
+#elif defined(__arm__) || defined(__aarch64__)
+    asm volatile("yield");
+#elif defined(__ppc64__)
+    asm volatile("or 27,27,27");
+#else
+#error "Unknown architecture"
+#endif
   }
 }
 
-- 
2.39.5