linux-kernel - Re: [PATCH V3] riscv: patch_text: Fixup last cpu should be master

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Date:   Wed, 06 Apr 2022 12:06:31 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...osinc.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     guoren@...nel.org, Arnd Bergmann <arnd@...db.de>,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, guoren@...ux.alibaba.com,
        mhiramat@...nel.org, stable@...r.kernel.org
Subject:     Re: [PATCH V3] riscv: patch_text: Fixup last cpu should be master

On Wed, 06 Apr 2022 11:13:36 PDT (-0700), Greg KH wrote:
> On Wed, Apr 06, 2022 at 10:16:49PM +0800, guoren@...nel.org wrote:
>> From: Guo Ren <guoren@...ux.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@...ux.alibaba.com>
>> Signed-off-by: Guo Ren <guoren@...nel.org>
>> Acked-by: Palmer Dabbelt <palmer@...osinc.com>
>> Reviewed-by: Masami Hiramatsu <mhiramat@...nel.org>
>> Cc: <stable@...r.kernel.org>
>> ---
>>  arch/riscv/kernel/patch.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> What commit id does this change fix?

I think it's been there since the beginning of our text patching, so

Fixes: 043cb41a85de ("riscv: introduce interfaces to patch kernel code")

seems like the best bet, but I'll go take another look before merging 
it.  That's confusing here, as I acked it, but that was for an earlier 
version that touched more than one arch so it was more ambiguous as to 
which tree it was going through (IIRC I said one of those "LMK if you 
want it through my tree, but here's an Ack in case someone else wants to 
take it" sort of things, as I usually do when it's ambiguous).

Without a changelog, cover letter, or the other patches in the set it's 
kind of hard to tell, though ;)