This is https://github.com/loongarch64/userspace-rcu/pull/2, yet to be
upstreamed but already reviewed and accepted by the LoongArch porting
community.

(and https://github.com/urcu/userspace-rcu/pull/11)

From 213197eea1a711da2f7cc0c04cdf33acb1b3c50e Mon Sep 17 00:00:00 2001
From: Wang Jing <wangjing@loongson.cn>
Date: Tue, 8 Jun 2021 19:44:49 +0800
Subject: [PATCH] Add LoongArch support

--- a/LICENSE
+++ b/LICENSE
@@ -44,6 +44,7 @@ MIT/X11 (BSD like) license apply to:
 compiler.h
 arch/s390.h
 uatomic/alpha.h
+uatomic/loongarch.h
 uatomic/mips.h
 uatomic/nios2.h
 uatomic/s390.h
--- a/README.md
+++ b/README.md
@@ -51,6 +51,7 @@ Currently, the following architectures are supported:
   - hppa/PA-RISC
   - m68k
   - RISC-V
+  - LoongArch
 
 Tested on:
 
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -7,6 +7,7 @@ nobase_include_HEADERS = \
 	urcu/arch.h \
 	urcu/arch/hppa.h \
 	urcu/arch/ia64.h \
+	urcu/arch/loongarch.h \
 	urcu/arch/m68k.h \
 	urcu/arch/mips.h \
 	urcu/arch/nios2.h \
@@ -67,6 +68,7 @@ nobase_include_HEADERS = \
 	urcu/uatomic.h \
 	urcu/uatomic/hppa.h \
 	urcu/uatomic/ia64.h \
+	urcu/uatomic/loongarch.h \
 	urcu/uatomic/m68k.h \
 	urcu/uatomic/mips.h \
 	urcu/uatomic/nios2.h \
--- a/include/urcu/arch.h
+++ b/include/urcu/arch.h
@@ -49,6 +49,7 @@
  * URCU_ARCH_HPPA : All HP PA-RISC variants
  * URCU_ARCH_M68K : All Motorola 68000 variants
  * URCU_ARCH_RISCV : All RISC-V variants
+ * URCU_ARCH_LOONGARCH : All LoongArch variants
  */
 
 #if (defined(__INTEL_OFFLOAD) || defined(__TARGET_ARCH_MIC) || defined(__MIC__))
@@ -157,6 +158,11 @@
 #define URCU_ARCH_RISCV 1
 #include <urcu/arch/riscv.h>
 
+#elif defined(__loongarch__)
+
+#define URCU_ARCH_LOONGARCH 1
+#include <urcu/arch/loongarch.h>
+
 #else
 #error "Cannot build: unrecognized architecture, see <urcu/arch.h>."
 #endif
--- /dev/null
+++ b/include/urcu/arch/loongarch.h
@@ -0,0 +1,49 @@
+#ifndef _URCU_ARCH_LOONGARCH_H
+#define _URCU_ARCH_LOONGARCH_H
+
+/*
+ * arch/loongarch.h: trivial definitions for the LoongArch architecture.
+ *
+ * Copyright (c) 2021 Wang Jing <wangjing@loongson.cn>
+ *
+ * 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; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * 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
+ */
+
+#include <urcu/compiler.h>
+#include <urcu/config.h>
+#include <urcu/syscall-compat.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdlib.h>
+#include <sys/time.h>
+
+/*
+ * On Linux, define the membarrier system call number if not yet available in
+ * the system headers.
+ */
+#if (defined(__linux__) && !defined(__NR_membarrier))
+#define __NR_membarrier		283
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#include <urcu/arch/generic.h>
+
+#endif /* _URCU_ARCH_LOONGARCH_H */
--- a/include/urcu/uatomic.h
+++ b/include/urcu/uatomic.h
@@ -51,6 +51,8 @@
 #include <urcu/uatomic/m68k.h>
 #elif defined(URCU_ARCH_RISCV)
 #include <urcu/uatomic/riscv.h>
+#elif defined(URCU_ARCH_LOONGARCH)
+#include <urcu/uatomic/loongarch.h>
 #else
 #error "Cannot build: unrecognized architecture, see <urcu/arch.h>."
 #endif
--- /dev/null
+++ b/include/urcu/uatomic/loongarch.h
@@ -0,0 +1,44 @@
+#ifndef _URCU_UATOMIC_ARCH_LOONGARCH_H
+#define _URCU_UATOMIC_ARCH_LOONGARCH_H
+
+/*
+ * Atomic exchange operations for the LoongArch architecture. Let GCC do it.
+ *
+ * Copyright (c) 2021 Wang Jing <wangjing@loongson.cn>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <urcu/compiler.h>
+#include <urcu/system.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define UATOMIC_HAS_ATOMIC_BYTE
+#define UATOMIC_HAS_ATOMIC_SHORT
+
+#ifdef __cplusplus
+}
+#endif
+
+#include <urcu/uatomic/generic.h>
+
+#endif /* _URCU_UATOMIC_ARCH_LOONGARCH_H */