[RFC PATCH 08/13] arm64: percpu: Implement preemptible void RMW ops
From: Mark Rutland <mark.rutland@arm.com>
Date: 2026-07-28 12:40:27
Also in:
lkml
Subsystem:
arm64 port (aarch64 architecture), per-cpu memory allocator, the rest · Maintainers:
Catalin Marinas, Will Deacon, Dennis Zhou, Tejun Heo, Christoph Lameter, Linus Torvalds
Use the PCPU GPR infrastructure to implement all of the RMW ops which do not return a value. Generated code before this patch (v7.2-rc4): | <outline_this_cpu_add_u64>: | paciasp | stp x29, x30, [sp, #-16]! | mrs x2, sp_el0 | mov x29, sp | ldr w3, [x2, #8] | add w3, w3, #0x1 | str w3, [x2, #8] | mrs x3, tpidr_el1 | add x0, x0, x3 | 1: ldxr x5, [x0] | add x5, x5, x1 | stxr w4, x5, [x0] | cbnz w4, 1b | ldr x0, [x2, #8] | sub x0, x0, #0x1 | str w0, [x2, #8] | cbz x0, 2f | ldr x0, [x2, #8] | cbnz x0, 3f | 2: bl preempt_schedule_notrace | 3: ldp x29, x30, [sp], #16 | autiasp | ret Generated code after this patch: | <outline_this_cpu_add_u64>: | mrs x2, sp_el0 | mov w4, #0xc80 | strh w4, [x2, #20] | mrs x4, tpidr_el1 | add x3, x0, x4 | 1: ldxr x6, [x3] | add x6, x6, x1 | stxr w5, x6, [x3] | cbnz w5, 1b | strh wzr, [x2, #20] | ret Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Ada Couprie Diaz <redacted> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Jinjie Ruan <redacted> Cc: Marc Zyngier <maz@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Vladimir Murzin <redacted> Cc: Will Deacon <will@kernel.org> Cc: Yang Shi <redacted> --- arch/arm64/include/asm/percpu.h | 52 ++++++++++++++++++++------------- 1 file changed, 32 insertions(+), 20 deletions(-)
diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h
index 32623ea676b96..7e9ab51561706 100644
--- a/arch/arm64/include/asm/percpu.h
+++ b/arch/arm64/include/asm/percpu.h@@ -140,23 +140,35 @@ static inline void __percpu_write_##sz(void __percpu *pcp, unsigned long val) \ #define __PERCPU_OP_CASE(w, sfx, name, sz, op_llsc, op_lse) \ static inline void \ -__percpu_##name##_case_##sz(void *ptr, unsigned long val) \ +__percpu_##name##_case_##sz(void __percpu *pcp, unsigned long val) \ { \ + u16 *gprs = ¤t_thread_info()->pcpu_gprs; \ + unsigned long addr; \ + unsigned long off; \ unsigned int loop; \ u##sz tmp; \ \ - asm volatile (ARM64_LSE_ATOMIC_INSN( \ + asm volatile ( \ + __PCPU_GPRS_BEGIN("%[gprs]", "%[pcp]", "%[off]", "%[addr]") \ + ARM64_LSE_ATOMIC_INSN( \ /* LL/SC */ \ - "1: ldxr" #sfx "\t%" #w "[tmp], %[ptr]\n" \ + "1: ldxr" #sfx "\t%" #w "[tmp], [%[addr]]\n" \ #op_llsc "\t%" #w "[tmp], %" #w "[tmp], %" #w "[val]\n" \ - " stxr" #sfx "\t%w[loop], %" #w "[tmp], %[ptr]\n" \ + " stxr" #sfx "\t%w[loop], %" #w "[tmp], [%[addr]]\n" \ " cbnz %w[loop], 1b", \ /* LSE atomics */ \ - #op_lse "\t%" #w "[val], %" #w "[tmp], %[ptr]\n" \ + #op_lse "\t%" #w "[val], %" #w "[tmp], [%[addr]]\n" \ __nops(3)) \ - : [loop] "=&r" (loop), [tmp] "=&r" (tmp), \ - [ptr] "+Q"(*(u##sz *)ptr) \ - : [val] "r" ((u##sz)(val))); \ + __PCPU_GPRS_END("%[gprs]") \ + : [gprs] "=Qo" (*gprs), \ + [addr] "=&r" (addr), \ + [off] "=&r" (off), \ + [loop] "=&r" (loop), \ + [tmp] "=&r" (tmp) \ + : [pcp] "r" (pcp), \ + [val] "r" ((u##sz)(val)) \ + : "memory" \ + ); \ } #define __PERCPU_RET_OP_CASE(w, sfx, name, sz, op_llsc, op_lse) \
@@ -273,13 +285,13 @@ PERCPU_RET_OP(add, add, ldadd) _pcp_wrap(__percpu_write_64, pcp, (unsigned long)val) #define this_cpu_add_1(pcp, val) \ - _pcp_protect(__percpu_add_case_8, pcp, val) + _pcp_wrap(__percpu_add_case_8, pcp, val) #define this_cpu_add_2(pcp, val) \ - _pcp_protect(__percpu_add_case_16, pcp, val) + _pcp_wrap(__percpu_add_case_16, pcp, val) #define this_cpu_add_4(pcp, val) \ - _pcp_protect(__percpu_add_case_32, pcp, val) + _pcp_wrap(__percpu_add_case_32, pcp, val) #define this_cpu_add_8(pcp, val) \ - _pcp_protect(__percpu_add_case_64, pcp, val) + _pcp_wrap(__percpu_add_case_64, pcp, val) #define this_cpu_add_return_1(pcp, val) \ _pcp_protect_return(__percpu_add_return_case_8, pcp, val)
@@ -291,22 +303,22 @@ PERCPU_RET_OP(add, add, ldadd) _pcp_protect_return(__percpu_add_return_case_64, pcp, val) #define this_cpu_and_1(pcp, val) \ - _pcp_protect(__percpu_andnot_case_8, pcp, ~val) + _pcp_wrap(__percpu_andnot_case_8, pcp, ~val) #define this_cpu_and_2(pcp, val) \ - _pcp_protect(__percpu_andnot_case_16, pcp, ~val) + _pcp_wrap(__percpu_andnot_case_16, pcp, ~val) #define this_cpu_and_4(pcp, val) \ - _pcp_protect(__percpu_andnot_case_32, pcp, ~val) + _pcp_wrap(__percpu_andnot_case_32, pcp, ~val) #define this_cpu_and_8(pcp, val) \ - _pcp_protect(__percpu_andnot_case_64, pcp, ~val) + _pcp_wrap(__percpu_andnot_case_64, pcp, ~val) #define this_cpu_or_1(pcp, val) \ - _pcp_protect(__percpu_or_case_8, pcp, val) + _pcp_wrap(__percpu_or_case_8, pcp, val) #define this_cpu_or_2(pcp, val) \ - _pcp_protect(__percpu_or_case_16, pcp, val) + _pcp_wrap(__percpu_or_case_16, pcp, val) #define this_cpu_or_4(pcp, val) \ - _pcp_protect(__percpu_or_case_32, pcp, val) + _pcp_wrap(__percpu_or_case_32, pcp, val) #define this_cpu_or_8(pcp, val) \ - _pcp_protect(__percpu_or_case_64, pcp, val) + _pcp_wrap(__percpu_or_case_64, pcp, val) #define this_cpu_xchg_1(pcp, val) \ _pcp_protect_return(xchg_relaxed, pcp, val)
--
2.30.2