Re: [PATCH 2/5] riscv: Add QUEUED_SPINLOCKS & QUEUED_RWLOCKS supported

Peter Zijlstra
2020-11-24T14:40:11Z

On Tue, Nov 24, 2020 at 01:43:54PM +0000, guoren@kernel.org wrote:
> diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild
> index 59dd7be..6f5f438 100644
> --- a/arch/riscv/include/asm/Kbuild
> +++ b/arch/riscv/include/asm/Kbuild
> @@ -6,3 +6,6 @@ generic-y += kvm_para.h
> generic-y += local64.h
> generic-y += user.h
> generic-y += vmlinux.lds.h
> +generic-y += mcs_spinlock.h
> +generic-y += qrwlock.h
> +generic-y += qspinlock.h
> diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h
> index 5609185..e178700 100644
> --- a/arch/riscv/include/asm/cmpxchg.h
> +++ b/arch/riscv/include/asm/cmpxchg.h
> @@ -16,7 +16,43 @@
> __typeof__(ptr) __ptr = (ptr); \
> __typeof__(new) __new = (new); \
> __typeof__(*(ptr)) __ret; \
> + register unsigned long __rc, tmp, align, addr; \
> switch (size) { \
> + case 2: \
> + align = ((unsigned long) __ptr & 0x3); \
> + addr = ((unsigned long) __ptr & ~0x3); \
> + if (align) { \
> + __asm__ __volatile__ ( \
> + "0: lr.w %0, 0(%z4)\n" \
> + " move %1, %0\n" \
> + " slli %1, %1, 16\n" \
> + " srli %1, %1, 16\n" \
> + " move %2, %z3\n" \
> + " slli %2, %2, 16\n" \
> + " or %1, %2, %1\n" \
> + " sc.w %2, %1, 0(%z4)\n" \
> + " bnez %2, 0b\n" \
> + " srli %0, %0, 16\n" \
> + : "=&r" (__ret), "=&r" (tmp), "=&r" (__rc) \
> + : "rJ" (__new), "rJ"(addr) \
> + : "memory"); \
> + } else { \
> + __asm__ __volatile__ ( \
> + "0: lr.w %0, (%z4)\n" \
> + " move %1, %0\n" \
> + " srli %1, %1, 16\n" \
> + " slli %1, %1, 16\n" \
> + " move %2, %z3\n" \
> + " or %1, %2, %1\n" \
> + " sc.w %2, %1, 0(%z4)\n" \
> + " bnez %2, 0b\n" \
> + " slli %0, %0, 16\n" \
> + " srli %0, %0, 16\n" \
> + : "=&r" (__ret), "=&r" (tmp), "=&r" (__rc) \
> + : "rJ" (__new), "rJ"(addr) \
> + : "memory"); \
> + } \
> + break; \
> case 4: \
> __asm__ __volatile__ ( \
> " amoswap.w %0, %2, %1\n" \

I'm pretty sure there's a handfull of implementations like this out
there... if only we could share.

Anyway, this too should be an independent patch.