x86: introduce rdtsc_barrier()

[linux-2.6-omap-h63xx.git] / include / asm-x86 / system.h

diff --git a/include/asm-x86/system.h b/include/asm-x86/system.h
index 6c7d1fda499549245d371a37d8832d2e1fac7ad3..39474f2957a3c872a4b49202bd42eee08fc94763 100644 (file)
--- a/include/asm-x86/system.h
+++ b/include/asm-x86/system.h
@@ -5,6 +5,7 @@
 #include <asm/segment.h>
 #include <asm/cpufeature.h>
 #include <asm/cmpxchg.h>
+#include <asm/nops.h>
 
 #include <linux/kernel.h>
 #include <linux/irqflags.h>
@@ -395,5 +396,17 @@ void default_idle(void);
 #define set_mb(var, value) do { var = value; barrier(); } while (0)
 #endif
 
+/*
+ * Stop RDTSC speculation. This is needed when you need to use RDTSC
+ * (or get_cycles or vread that possibly accesses the TSC) in a defined
+ * code region.
+ *
+ * (Could use an alternative three way for this if there was one.)
+ */
+static inline void rdtsc_barrier(void)
+{
+       alternative(ASM_NOP3, "mfence", X86_FEATURE_MFENCE_RDTSC);
+       alternative(ASM_NOP3, "lfence", X86_FEATURE_LFENCE_RDTSC);
+}
 
 #endif