Merge pull request ceph#14337 from smithfarm/wip-19492

common: support s390 and unknown architectures in spin-wait loop

Reviewed-by: Kefu Chai <[email protected]>
Reviewed-by: Brad Hubbard <[email protected]>

src/common/simple_spin.cc

@@ -18,25 +18,42 @@
 #include <stdint.h>
 #include <pthread.h>
 
-void simple_spin_lock(simple_spinlock_t *lock)
+namespace {
+
+#if !defined(__i386__) && !defined(__x86_64__) && !defined(__arm__) && !defined(__aarch64__) && !defined(__powerpc__) && !defined(__ppc__) && !defined(__s390__) && !defined(__s390x__)
+static uint32_t bar = 13;
+static uint32_t *foo = &bar;
+#endif
+
+void cpu_relax()
 {
-  while(1) {
-    __sync_synchronize();
-    uint32_t oldval = *lock;
-    if (oldval == 0) {
-      if (__sync_bool_compare_and_swap(lock, 0, 1))
-	return;
-    }
-    // delay
 #if defined(__i386__) || defined(__x86_64__)
     asm volatile("pause");
 #elif defined(__arm__) || defined(__aarch64__)
     asm volatile("yield");
 #elif defined(__powerpc__) || defined(__ppc__)
     asm volatile("or 27,27,27");
+#elif defined(__s390__) || defined(__s390x__)
+    asm volatile("": : :"memory");
 #else
-#error "Unknown architecture"
+    for (int i = 0; i < 100000; i++) {
+      *foo = (*foo * 33) + 17;
+    }
 #endif
+}
+
+} // namespace
+
+void simple_spin_lock(simple_spinlock_t *lock)
+{
+  while (1) {
+    __sync_synchronize();
+    uint32_t oldval = *lock;
+    if (oldval == 0) {
+      if (__sync_bool_compare_and_swap(lock, 0, 1))
+	return;
+    }
+    cpu_relax();
   }
 }