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SubjectRe: [PATCH V3] riscv: patch_text: Fixup last cpu should be master
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On Wed, 06 Apr 2022 07:16:49 PDT (-0700), guoren@kernel.org wrote:
> From: Guo Ren <guoren@linux.alibaba.com>
>
> These patch_text implementations are using stop_machine_cpuslocked
> infrastructure with atomic cpu_count. The original idea: When the
> master CPU patch_text, the others should wait for it. But current
> implementation is using the first CPU as master, which couldn't
> guarantee the remaining CPUs are waiting. This patch changes the
> last CPU as the master to solve the potential risk.
>
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@kernel.org>
> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: <stable@vger.kernel.org>
> ---
> arch/riscv/kernel/patch.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
> index 0b552873a577..765004b60513 100644
> --- a/arch/riscv/kernel/patch.c
> +++ b/arch/riscv/kernel/patch.c
> @@ -104,7 +104,7 @@ static int patch_text_cb(void *data)
> struct patch_insn *patch = data;
> int ret = 0;
>
> - if (atomic_inc_return(&patch->cpu_count) == 1) {
> + if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
> ret =
> patch_text_nosync(patch->addr, &patch->insn,
> GET_INSN_LENGTH(patch->insn));

Thanks, this is on fixes.

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