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Message-Id: <20250618034328.21904-2-cuiyunhui@bytedance.com>
Date: Wed, 18 Jun 2025 11:43:28 +0800
From: Yunhui Cui <cuiyunhui@...edance.com>
To: yury.norov@...il.com,
linux@...musvillemoes.dk,
paul.walmsley@...ive.com,
palmer@...belt.com,
aou@...s.berkeley.edu,
alex@...ti.fr,
linux-riscv@...ts.infradead.org,
linux-kernel@...r.kernel.org,
dennis@...nel.org,
tj@...nel.org,
cl@...two.org,
linux-mm@...ck.org
Cc: Yunhui Cui <cuiyunhui@...edance.com>
Subject: [PATCH RFC 2/2] riscv: introduce percpu.h into include/asm
Current percpu operations rely on generic implementations, where
raw_local_irq_save() introduces substantial overhead. Optimization
is achieved through atomic operations and preemption disabling.
Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
---
arch/riscv/include/asm/percpu.h | 138 ++++++++++++++++++++++++++++++++
1 file changed, 138 insertions(+)
create mode 100644 arch/riscv/include/asm/percpu.h
diff --git a/arch/riscv/include/asm/percpu.h b/arch/riscv/include/asm/percpu.h
new file mode 100644
index 0000000000000..423c0d01f874c
--- /dev/null
+++ b/arch/riscv/include/asm/percpu.h
@@ -0,0 +1,138 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __ASM_PERCPU_H
+#define __ASM_PERCPU_H
+
+#include <linux/preempt.h>
+
+#define PERCPU_RW_OPS(sz) \
+static inline unsigned long __percpu_read_##sz(void *ptr) \
+{ \
+ return READ_ONCE(*(u##sz *)ptr); \
+} \
+ \
+static inline void __percpu_write_##sz(void *ptr, unsigned long val) \
+{ \
+ WRITE_ONCE(*(u##sz *)ptr, (u##sz)val); \
+}
+
+#define __PERCPU_AMO_OP_CASE(sfx, name, sz, amo_insn) \
+static inline void \
+__percpu_##name##_amo_case_##sz(void *ptr, unsigned long val) \
+{ \
+ asm volatile ( \
+ "amo" #amo_insn #sfx " zero, %[val], %[ptr]" \
+ : [ptr] "+A" (*(u##sz *)ptr) \
+ : [val] "r" ((u##sz)(val)) \
+ : "memory"); \
+}
+
+#define __PERCPU_AMO_RET_OP_CASE(sfx, name, sz, amo_insn) \
+static inline u##sz \
+__percpu_##name##_return_amo_case_##sz(void *ptr, unsigned long val) \
+{ \
+ register u##sz ret; \
+ \
+ asm volatile ( \
+ "amo" #amo_insn #sfx " %[ret], %[val], %[ptr]" \
+ : [ptr] "+A" (*(u##sz *)ptr), [ret] "=r" (ret) \
+ : [val] "r" ((u##sz)(val)) \
+ : "memory"); \
+ \
+ return ret + val; \
+}
+
+#define PERCPU_OP(name, amo_insn) \
+ __PERCPU_AMO_OP_CASE(.b, name, 8, amo_insn) \
+ __PERCPU_AMO_OP_CASE(.h, name, 16, amo_insn) \
+ __PERCPU_AMO_OP_CASE(.w, name, 32, amo_insn) \
+ __PERCPU_AMO_OP_CASE(.d, name, 64, amo_insn) \
+
+#define PERCPU_RET_OP(name, amo_insn) \
+ __PERCPU_AMO_RET_OP_CASE(.b, name, 8, amo_insn) \
+ __PERCPU_AMO_RET_OP_CASE(.h, name, 16, amo_insn) \
+ __PERCPU_AMO_RET_OP_CASE(.w, name, 32, amo_insn) \
+ __PERCPU_AMO_RET_OP_CASE(.d, name, 64, amo_insn)
+
+PERCPU_RW_OPS(8)
+PERCPU_RW_OPS(16)
+PERCPU_RW_OPS(32)
+PERCPU_RW_OPS(64)
+
+PERCPU_OP(add, add)
+PERCPU_OP(andnot, and)
+PERCPU_OP(or, or)
+PERCPU_RET_OP(add, add)
+
+#undef PERCPU_RW_OPS
+#undef __PERCPU_AMO_OP_CASE
+#undef __PERCPU_AMO_RET_OP_CASE
+#undef PERCPU_OP
+#undef PERCPU_RET_OP
+
+#define _pcp_protect(op, pcp, ...) \
+({ \
+ preempt_disable_notrace(); \
+ op(raw_cpu_ptr(&(pcp)), __VA_ARGS__); \
+ preempt_enable_notrace(); \
+})
+
+#define _pcp_protect_return(op, pcp, args...) \
+({ \
+ typeof(pcp) __retval; \
+ preempt_disable_notrace(); \
+ __retval = (typeof(pcp))op(raw_cpu_ptr(&(pcp)), ##args); \
+ preempt_enable_notrace(); \
+ __retval; \
+})
+
+#define this_cpu_read_1(pcp) _pcp_protect_return(__percpu_read_8, pcp)
+#define this_cpu_read_2(pcp) _pcp_protect_return(__percpu_read_16, pcp)
+#define this_cpu_read_4(pcp) _pcp_protect_return(__percpu_read_32, pcp)
+#define this_cpu_read_8(pcp) _pcp_protect_return(__percpu_read_64, pcp)
+
+#define this_cpu_write_1(pcp, val) _pcp_protect(__percpu_write_8, pcp, (unsigned long)val)
+#define this_cpu_write_2(pcp, val) _pcp_protect(__percpu_write_16, pcp, (unsigned long)val)
+#define this_cpu_write_4(pcp, val) _pcp_protect(__percpu_write_32, pcp, (unsigned long)val)
+#define this_cpu_write_8(pcp, val) _pcp_protect(__percpu_write_64, pcp, (unsigned long)val)
+
+#define this_cpu_add_1(pcp, val) _pcp_protect(__percpu_add_amo_case_8, pcp, val)
+#define this_cpu_add_2(pcp, val) _pcp_protect(__percpu_add_amo_case_16, pcp, val)
+#define this_cpu_add_4(pcp, val) _pcp_protect(__percpu_add_amo_case_32, pcp, val)
+#define this_cpu_add_8(pcp, val) _pcp_protect(__percpu_add_amo_case_64, pcp, val)
+
+#define this_cpu_add_return_1(pcp, val) \
+_pcp_protect_return(__percpu_add_return_amo_case_8, pcp, val)
+
+#define this_cpu_add_return_2(pcp, val) \
+_pcp_protect_return(__percpu_add_return_amo_case_16, pcp, val)
+
+#define this_cpu_add_return_4(pcp, val) \
+_pcp_protect_return(__percpu_add_return_amo_case_32, pcp, val)
+
+#define this_cpu_add_return_8(pcp, val) \
+_pcp_protect_return(__percpu_add_return_amo_case_64, pcp, val)
+
+#define this_cpu_and_1(pcp, val) _pcp_protect(__percpu_andnot_amo_case_8, pcp, ~val)
+#define this_cpu_and_2(pcp, val) _pcp_protect(__percpu_andnot_amo_case_16, pcp, ~val)
+#define this_cpu_and_4(pcp, val) _pcp_protect(__percpu_andnot_amo_case_32, pcp, ~val)
+#define this_cpu_and_8(pcp, val) _pcp_protect(__percpu_andnot_amo_case_64, pcp, ~val)
+
+#define this_cpu_or_1(pcp, val) _pcp_protect(__percpu_or_amo_case_8, pcp, val)
+#define this_cpu_or_2(pcp, val) _pcp_protect(__percpu_or_amo_case_16, pcp, val)
+#define this_cpu_or_4(pcp, val) _pcp_protect(__percpu_or_amo_case_32, pcp, val)
+#define this_cpu_or_8(pcp, val) _pcp_protect(__percpu_or_amo_case_64, pcp, val)
+
+#define this_cpu_xchg_1(pcp, val) _pcp_protect_return(xchg_relaxed, pcp, val)
+#define this_cpu_xchg_2(pcp, val) _pcp_protect_return(xchg_relaxed, pcp, val)
+#define this_cpu_xchg_4(pcp, val) _pcp_protect_return(xchg_relaxed, pcp, val)
+#define this_cpu_xchg_8(pcp, val) _pcp_protect_return(xchg_relaxed, pcp, val)
+
+#define this_cpu_cmpxchg_1(pcp, o, n) _pcp_protect_return(cmpxchg_relaxed, pcp, o, n)
+#define this_cpu_cmpxchg_2(pcp, o, n) _pcp_protect_return(cmpxchg_relaxed, pcp, o, n)
+#define this_cpu_cmpxchg_4(pcp, o, n) _pcp_protect_return(cmpxchg_relaxed, pcp, o, n)
+#define this_cpu_cmpxchg_8(pcp, o, n) _pcp_protect_return(cmpxchg_relaxed, pcp, o, n)
+
+#include <asm-generic/percpu.h>
+
+#endif /* __ASM_PERCPU_H */
--
2.39.5
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