Cleanup: remove redundant memory barrier

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

diff --git a/libringbuffer/getcpu.h b/libringbuffer/getcpu.h
index 3474bfe0c04f9f218eac190b001b08600f9d8272..7b009dc6cf38efefd67aece71a8308a66a351efb 100644 (file)
--- a/libringbuffer/getcpu.h
+++ b/libringbuffer/getcpu.h
@@ -20,8 +20,15 @@
  */
 
 #include <urcu/compiler.h>
+#include <urcu/system.h>
+#include <urcu/arch.h>
+#include <config.h>
 
-#ifdef UST_VALGRIND
+void lttng_ust_getcpu_init(void);
+
+extern int (*lttng_get_cpu)(void);
+
+#ifdef LTTNG_UST_DEBUG_VALGRIND
 
 /*
  * Fallback on cpu 0 if liblttng-ust is build with Valgrind support.
@@ -29,7 +36,7 @@
  * migration, so it is only statistically accurate.
  */
 static inline
-int lttng_ust_get_cpu(void)
+int lttng_ust_get_cpu_internal(void)
 {
        return 0;
 }
@@ -41,30 +48,30 @@ int lttng_ust_get_cpu(void)
  */
 #ifdef __linux__
 
-#ifdef __UCLIBC__
+#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 c;
+       return cpu;
 }
-#else /* __UCLIBC__ */
+#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(void)
+int lttng_ust_get_cpu_internal(void)
 {
        int cpu;
 
@@ -73,16 +80,16 @@ int lttng_ust_get_cpu(void)
                return 0;
        return cpu;
 }
-#endif /* __UCLIBC__ */
+#endif /* HAVE_SCHED_GETCPU */
 
-#elif defined(__FreeBSD__)
+#elif (defined(__FreeBSD__) || defined(__CYGWIN__))
 
 /*
- * FreeBSD does not allow query of CPU ID. Always use CPU number 0, with
- * the assocated performance degradation on SMP.
+ * 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(void)
+int lttng_ust_get_cpu_internal(void)
 {
        return 0;
 }
@@ -93,4 +100,16 @@ int lttng_ust_get_cpu(void)
 
 #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 */