Add ring buffer comment about shm

[lttng-ust.git] / include / ust / core.h

diff --git a/include/ust/core.h b/include/ust/core.h
index d1fdb2dfdb2c7faa9eb6805a37b6f99bace22a22..10e864f18b22a25493b5aa13f6faa3590768724c 100644 (file)
--- a/include/ust/core.h
+++ b/include/ust/core.h
@@ -3,11 +3,12 @@
 
 /*
  * Copyright (C) 2010  Pierre-Marc Fournier
+ * Copyright (C) 2011  Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; either
- * version 2.1 of the License, or (at your option) any later version.
+ * License as published by the Free Software Foundation; version 2.1 of
+ * the License.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ -138,4 +139,35 @@ static __inline__ int get_count_order(unsigned int count)
 #define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
 #endif
 
+#ifndef UST_VALGRIND
+
+static __inline__ int ust_get_cpu(void)
+{
+       int cpu;
+
+       cpu = sched_getcpu();
+       if (likely(cpu >= 0))
+               return cpu;
+       /*
+        * If getcpu(2) is not implemented in the Kernel use CPU 0 as fallback.
+        */
+       return 0;
+}
+
+#else  /* #else #ifndef UST_VALGRIND */
+
+static __inline__ int ust_get_cpu(void)
+{
+       /*
+        * Valgrind does not support the sched_getcpu() vsyscall.
+        * It causes it to detect a segfault in the program and stop it.
+        * So if we want to check libust with valgrind, we have to refrain
+        * from using this call. TODO: it would probably be better to return
+        * other values too, to better test it.
+        */
+       return 0;
+}
+
+#endif /* #else #ifndef UST_VALGRIND */
+
 #endif /* UST_CORE_H */