linux-kernel - Re: [PATCH -next] riscv: Enable ARCH_HAVE_NMI_SAFE

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Message-ID: <fa509f25-cbd6-41d5-8f34-bbd45062a8b7@huawei.com>
Date: Thu, 17 Jul 2025 10:00:51 +0800
From: Pu Lehui <pulehui@...wei.com>
To: Palmer Dabbelt <palmer@...belt.com>, Alexandre Ghiti <alex@...ti.fr>,
	<linux-riscv@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
CC: Pu Lehui <pulehui@...weicloud.com>
Subject: Re: [PATCH -next] riscv: Enable ARCH_HAVE_NMI_SAFE_CMPXCHG



On 2025/7/11 17:04, Pu Lehui wrote:
> From: Pu Lehui <pulehui@...wei.com>
> 
> The implement of cmpxchg() in riscv is based on atomic primitives and
> has NMI-safe features, so it can be used safely in the in_nmi context.
> ftrace's ringbuffer relies on NMI-safe cmpxchg() in the NMI context.
> Currently, in_nmi() is true when riscv kprobe is in trap-based mode, so
> this config needs to be selected, otherwise kprobetrace will not be

Gentle ping~

The issue can be reproduced by the following steps:

cd /sys/kernel/debug/tracing/
echo 'p do_nanosleep' > kprobe_events
echo 1 > events/kprobes/enable
sleep 1
cat trace # trace log will not show without this patch

> available.
> 
> Signed-off-by: Pu Lehui <pulehui@...wei.com>
> ---
>   arch/riscv/Kconfig | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 36061f4732b7..0e2dfa98338a 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -23,6 +23,7 @@ config RISCV
>   	select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG
>   	select ARCH_ENABLE_SPLIT_PMD_PTLOCK if PGTABLE_LEVELS > 2
>   	select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE
> +	select ARCH_HAVE_NMI_SAFE_CMPXCHG
>   	select ARCH_HAS_BINFMT_FLAT
>   	select ARCH_HAS_CRC32 if RISCV_ISA_ZBC
>   	select ARCH_HAS_CRC64 if 64BIT && RISCV_ISA_ZBC