linux-kernel - Re: [PATCH] Documentation/x86: Update split lock documentation

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Message-ID: <65ce7063-d966-efea-6a39-db81da6b05aa@igalia.com>
Date:   Thu, 16 Mar 2023 10:01:08 -0300
From:   "Guilherme G. Piccoli" <gpiccoli@...lia.com>
To:     Fenghua Yu <fenghua.yu@...el.com>, Tony Luck <tony.luck@...el.com>,
        Jonathan Corbet <corbet@....net>
Cc:     x86@...nel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, patches@...ts.linux.dev
Subject: Re: [PATCH] Documentation/x86: Update split lock documentation

On 15/03/2023 20:13, Fenghua Yu wrote:
> Hi, Tony,
> 
> On 3/15/23 15:57, Tony Luck wrote:
>> commit b041b525dab9 ("x86/split_lock: Make life miserable for split
>> lockers") added a delay and serialization of cplit locks. Commit
>                                               s/cplit/split/
> 
>> 727209376f49 ("x86/split_lock: Add sysctl to control the misery mode")
>> provided a sysctl to turn off the misery.
>>
>> Update the split lock documentation to describe the current state of
>> the code.
>>
>> Signed-off-by: Tony Luck <tony.luck@...el.com>
>> ---
>>   Documentation/x86/buslock.rst | 10 ++++++++--
>>   1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/x86/buslock.rst b/Documentation/x86/buslock.rst
>> index 7c051e714943..31ec0ef78086 100644
>> --- a/Documentation/x86/buslock.rst
>> +++ b/Documentation/x86/buslock.rst
>> @@ -53,8 +53,14 @@ parameter "split_lock_detect". Here is a summary of different options:
>>   |off	  	   |Do nothing			|Do nothing		|
>>   +------------------+----------------------------+-----------------------+
>>   |warn		   |Kernel OOPs			|Warn once per task and |
>> -|(default)	   |Warn once per task and	|and continues to run.  |
>> -|		   |disable future checking	|			|
>> +|(default)	   |Warn once per task, add a	|and continues to run.  |
>> +|		   |delay, add synchronization	|			|
>> +|		   |to prevent more than one	|			|
>> +|		   |core from executing a	|			|
>> +|		   |split lock in parallel.	|			|
>> +|		   |sysctl split_lock_mitigate	|			|
>> +|		   |can be used to avoid the	|			|
>> +|		   |delay and synchronization	|			|
>>   |		   |When both features are	|			|
>>   |		   |supported, warn in #AC	|			|
>>   +------------------+----------------------------+-----------------------+
> 
> Other than the typo, looks good to me.
> 
> Thanks.
> 
> -Fenghua

Thanks for fixing the documentation Tony! Also looks great for me.
Cheers,


Guilherme