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Date:   Mon, 27 Jul 2020 13:19:40 -0700 (PDT)
Subject:     Re: [PATCH] riscv: Grab text_mutex before patching jump-labels
In-Reply-To: <20200723163628.82794-1-kernel@esmil.dk>
CC:     linux-riscv@lists.infradead.org, kernel@esmil.dk,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Bjorn Topel <bjorn.topel@gmail.com>,
        linux-kernel@vger.kernel.org
From:   Palmer Dabbelt <palmer@dabbelt.com>
To:     kernel@esmil.dk
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On Thu, 23 Jul 2020 09:36:28 PDT (-0700), kernel@esmil.dk wrote:
> Like other arch's we use patch_text_nosync or equivalent
> to patch the jump-labels, but also like other arch's we
> need to hold the text_mutex before calling that.
>
> Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
> ---
>
> Fixes: b6e0878a4ec8 ("riscv: Add jump-label implementation")
> ..that is already in riscv/for-next.
>
> Palmer: Sorry, I didn't notice this before. Feel free to
> squash this into the commit above if you like.
> ---
>  arch/riscv/kernel/jump_label.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/jump_label.c b/arch/riscv/kernel/jump_label.c
> index 1bab1abc1aa5..20e09056d141 100644
> --- a/arch/riscv/kernel/jump_label.c
> +++ b/arch/riscv/kernel/jump_label.c
> @@ -4,8 +4,10 @@
>   *
>   * Based on arch/arm64/kernel/jump_label.c
>   */
> -#include <linux/kernel.h>
>  #include <linux/jump_label.h>
> +#include <linux/kernel.h>
> +#include <linux/memory.h>
> +#include <linux/mutex.h>
>  #include <asm/bug.h>
>  #include <asm/patch.h>
>
> @@ -33,7 +35,9 @@ void arch_jump_label_transform(struct jump_entry *entry,
>  		insn = RISCV_INSN_NOP;
>  	}
>
> +	mutex_lock(&text_mutex);
>  	patch_text_nosync(addr, &insn, sizeof(insn));
> +	mutex_unlock(&text_mutex);
>  }
>
>  void arch_jump_label_transform_static(struct jump_entry *entry,

I've just put this on for-next as is.  I generally try to avoid rebasing stuff,
but I think I saw a message today about a patch I put there prematurely so I
might have to rewrite history anyway.  If I do I'll squash it and a few other
small fixes.

Thanks!