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From: Yunsheng Lin <linyunsheng@huawei.com>
To: <davem@davemloft.net>, <kuba@kernel.org>, <mst@redhat.com>,
	<jasowang@redhat.com>
Cc: <nickhu@andestech.com>, <green.hu@gmail.com>,
	<deanbo422@gmail.com>, <akpm@linux-foundation.org>,
	<yury.norov@gmail.com>, <andriy.shevchenko@linux.intel.com>,
	<ojeda@kernel.org>, <ndesaulniers@gooogle.com>, <joe@perches.com>,
	<linux-kernel@vger.kernel.org>,
	<virtualization@lists.linux-foundation.org>,
	<netdev@vger.kernel.org>, <linuxarm@openeuler.org>
Subject: [PATCH v2 3/4] tools headers UAPI: add cpu_relax() implementation for x86 and arm64
Date: Tue, 20 Jul 2021 10:21:48 +0800	[thread overview]
Message-ID: <1626747709-34013-4-git-send-email-linyunsheng@huawei.com> (raw)
In-Reply-To: <1626747709-34013-1-git-send-email-linyunsheng@huawei.com>

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@huawei.com>
---
 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


  parent reply	other threads:[~2021-07-20  2:41 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-20  2:21 [PATCH v2 0/4] refactor the ringtest testing for ptr_ring Yunsheng Lin
2021-07-20  2:21 ` [PATCH v2 1/4] tools headers UAPI: add cache aligning related macro Yunsheng Lin
2021-07-20  2:21 ` [PATCH v2 2/4] tools headers UAPI: add kmalloc/vmalloc related interface Yunsheng Lin
2021-07-20  2:21 ` Yunsheng Lin [this message]
2021-07-21 20:53   ` [PATCH v2 3/4] tools headers UAPI: add cpu_relax() implementation for x86 and arm64 David Laight
2021-07-22  8:18     ` Yunsheng Lin
2021-07-22  8:45       ` David Laight
2021-07-20  2:21 ` [PATCH v2 4/4] tools/virtio: use common infrastructure to build ptr_ring.h Yunsheng Lin

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