linux-kernel - Re: [PATCH] riscv: force __cpu_up_ variables to put in data section

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Message-ID: <CAHCEehJ2pbGUe79Kq6q5DFSHNWwg0FEOinqqL=PRNmTt1nT_kg@mail.gmail.com>
Date:   Thu, 30 Apr 2020 22:45:47 +0800
From:   Greentime Hu <greentime.hu@...ive.com>
To:     Zong Li <zong.li@...ive.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] riscv: force __cpu_up_ variables to put in data section

Zong Li <zong.li@...ive.com> 於 2020年4月30日 週四 下午5:53寫道：
>
> Put __cpu_up_stack_pointer and __cpu_up_task_pointer in data section.
> Currently, these two variables are put in bss section, there is a
> potential risk that secondary harts get the uninitialized value before
> main hart finishing the bss clearing. In this case, all secondary
> harts would go through the waiting loop and enable the MMU before
> main hart set up the page table.
>
> Signed-off-by: Zong Li <zong.li@...ive.com>
> ---
>  arch/riscv/kernel/cpu_ops.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/kernel/cpu_ops.c b/arch/riscv/kernel/cpu_ops.c
> index c4c33bf02369..0ec22354018c 100644
> --- a/arch/riscv/kernel/cpu_ops.c
> +++ b/arch/riscv/kernel/cpu_ops.c
> @@ -15,8 +15,8 @@
>
>  const struct cpu_operations *cpu_ops[NR_CPUS] __ro_after_init;
>
> -void *__cpu_up_stack_pointer[NR_CPUS];
> -void *__cpu_up_task_pointer[NR_CPUS];
> +void *__cpu_up_stack_pointer[NR_CPUS] __section(.data);
> +void *__cpu_up_task_pointer[NR_CPUS] __section(.data);
>
>  extern const struct cpu_operations cpu_ops_sbi;
>  extern const struct cpu_operations cpu_ops_spinwait;

Reviewed-by: Greentime Hu <greentime.hu@...ive.com>