[PATCH v2 3/4] tools headers UAPI: add cpu_relax() implementation for x86 and arm64

From: Yunsheng Lin
Date: Mon Jul 19 2021 - 22:41:52 EST


As x86 and arm64 is the two available systems that I can build
and test the cpu_relax() implementation, so only add cpu_relax()
implementation for x86 and arm64, other arches can be added easily
when needed.

Signed-off-by: Yunsheng Lin <linyunsheng@xxxxxxxxxx>
---
tools/include/asm/processor.h | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
create mode 100644 tools/include/asm/processor.h

diff --git a/tools/include/asm/processor.h b/tools/include/asm/processor.h
new file mode 100644
index 0000000..f9b3902
--- /dev/null
+++ b/tools/include/asm/processor.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __TOOLS_LINUX_ASM_PROCESSOR_H
+#define __TOOLS_LINUX_ASM_PROCESSOR_H
+
+#if defined(__i386__) || defined(__x86_64__)
+/* REP NOP (PAUSE) is a good thing to insert into busy-wait loops. */
+static __always_inline void rep_nop(void)
+{
+ asm volatile("rep; nop" ::: "memory");
+}
+
+static __always_inline void cpu_relax(void)
+{
+ rep_nop();
+}
+#elif defined(__aarch64__)
+static inline void cpu_relax(void)
+{
+ asm volatile("yield" ::: "memory");
+}
+#else
+#error "Architecture not supported"
+#endif
+
+#endif
--
2.7.4