Move to kernel style SPDX license identifiers

[lttng-ust.git] / libringbuffer / getcpu.h

diff --git a/libringbuffer/getcpu.h b/libringbuffer/getcpu.h
index 104ba7601c6bc58598833d4e7acc9374e6262e4f..bb815e66141171aa4af62595dcec4a9d66184d4c 100644 (file)
--- a/libringbuffer/getcpu.h
+++ b/libringbuffer/getcpu.h
@@ -1,28 +1,21 @@
-#ifndef _LTTNG_GETCPU_H
-#define _LTTNG_GETCPU_H
-
 /*
- * Copyright (c) 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * SPDX-License-Identifier: LGPL-2.1-only
  *
- * 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; only
- * 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
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  */
 
+#ifndef _LTTNG_GETCPU_H
+#define _LTTNG_GETCPU_H
+
 #include <urcu/compiler.h>
-#include <sched.h>
+#include <urcu/system.h>
+#include <urcu/arch.h>
+
+void lttng_ust_getcpu_init(void);
+
+extern int (*lttng_get_cpu)(void);
 
-#ifdef UST_VALGRIND
+#ifdef LTTNG_UST_DEBUG_VALGRIND
 
 /*
  * Fallback on cpu 0 if liblttng-ust is build with Valgrind support.
@@ -30,18 +23,42 @@
  * migration, so it is only statistically accurate.
  */
 static inline
-int lttng_ust_get_cpu(void)
+int lttng_ust_get_cpu_internal(void)
 {
        return 0;
 }
 
 #else
 
+/*
+ * sched_getcpu.
+ */
+#ifdef __linux__
+
+#if !HAVE_SCHED_GETCPU
+#include <sys/syscall.h>
+#define __getcpu(cpu, node, cache)     syscall(__NR_getcpu, cpu, node, cache)
 /*
  * If getcpu is not implemented in the kernel, use cpu 0 as fallback.
  */
 static inline
-int lttng_ust_get_cpu(void)
+int lttng_ust_get_cpu_internal(void)
+{
+       int cpu, ret;
+
+       ret = __getcpu(&cpu, NULL, NULL);
+       if (caa_unlikely(ret < 0))
+               return 0;
+       return cpu;
+}
+#else /* HAVE_SCHED_GETCPU */
+#include <sched.h>
+
+/*
+ * If getcpu is not implemented in the kernel, use cpu 0 as fallback.
+ */
+static inline
+int lttng_ust_get_cpu_internal(void)
 {
        int cpu;
 
@@ -50,7 +67,36 @@ int lttng_ust_get_cpu(void)
                return 0;
        return cpu;
 }
+#endif /* HAVE_SCHED_GETCPU */
+
+#elif (defined(__FreeBSD__) || defined(__CYGWIN__))
+
+/*
+ * FreeBSD and Cygwin do not allow query of CPU ID. Always use CPU
+ * number 0, with the assocated performance degradation on SMP.
+ */
+static inline
+int lttng_ust_get_cpu_internal(void)
+{
+       return 0;
+}
+
+#else
+#error "Please add support for your OS into liblttng-ust/compat.h."
+#endif
 
 #endif
 
+static inline
+int lttng_ust_get_cpu(void)
+{
+       int (*getcpu)(void) = CMM_LOAD_SHARED(lttng_get_cpu);
+
+       if (caa_likely(!getcpu)) {
+               return lttng_ust_get_cpu_internal();
+       } else {
+               return getcpu();
+       }
+}
+
 #endif /* _LTTNG_GETCPU_H */