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Date: Tue, 28 Sep 2021 21:14:51 -0300
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Subject: Re: [PATCH v2 4/4] powerpc/pseries/cpuhp: remove obsolete comment
 from pseries_cpu_die
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To: Nathan Lynch <nathanl@linux.ibm.com>, linuxppc-dev@lists.ozlabs.org
References: <20210927201933.76786-1-nathanl@linux.ibm.com>
 <20210927201933.76786-5-nathanl@linux.ibm.com>
From: Daniel Henrique Barboza <danielhb413@gmail.com>
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On 9/27/21 17:19, Nathan Lynch wrote:
> This comment likely refers to the obsolete DLPAR workflow where some
> resource state transitions were driven more directly from user space
> utilities, but it also seems to contradict itself: "Change isolate state to
> Isolate [...]" is at odds with the preceding sentences, and it does not
> relate at all to the code that follows.


This comment was added by commit 413f7c405a34, a 2006 commit where Mike
Ellerman moved code from platform/pseries/smp.c into hotplug-cpu.c.

I checked the original code back in smp.c and this comment was added there
by commit 1da177e4c3f41, which is Linus's initial git commit, where he mentions
that he didn't bothered with full history (although it is available somewhere,
allegedly).

This is enough to say that we can't easily see the history behind this comment.
I also believe that we're better of without it since it doesn't make sense
with the current codebase.


Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>

> 
> Remove it to prevent confusion.
> 
> Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
> ---
>   arch/powerpc/platforms/pseries/hotplug-cpu.c | 5 -----
>   1 file changed, 5 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
> index b50f3e9aa259..5ab44600c8d3 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
> @@ -137,11 +137,6 @@ static void pseries_cpu_die(unsigned int cpu)
>   			cpu, pcpu);
>   	}
>   
> -	/* Isolation and deallocation are definitely done by
> -	 * drslot_chrp_cpu.  If they were not they would be
> -	 * done here.  Change isolate state to Isolate and
> -	 * change allocation-state to Unusable.
> -	 */
>   	paca_ptrs[cpu]->cpu_start = 0;
>   }
>   
>