linux-kernel - Re: [PATCH v1 1/1] printk: always output coreid in caller information

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Date:   Wed, 19 May 2021 17:24:48 +0800
From:   Ruifeng Zhang <ruifeng.zhang0110@...il.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     pmladek@...e.com, senozhatsky@...omium.org, rostedt@...dmis.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ruifeng.zhang1@...soc.com, nianfu.bai@...soc.com,
        orson.zhai@...soc.com
Subject: Re: [PATCH v1 1/1] printk: always output coreid in caller information

Dear John,

Thanks for your review and reply.

I am glad to know the Linux Community had been discussing this requirements.

My patch really has some problems you proposed.

I will pay attention to the modification about extra message output in printk.

Thanks.

Best regards,
Ruifeng

John Ogness <john.ogness@...utronix.de> 于2021年5月19日周三 下午4:25写道：
>
> Hello Ruifeng,
>
> On 2021-05-19, Ruifeng Zhang <ruifeng.zhang0110@...il.com> wrote:
> > From: Ruifeng Zhang <ruifeng.zhang1@...soc.com>
> >
> > Sometimes we want to know which cpu the process is running
> > on when the log output, rather than the thread id.  So add
> > the processor id output always in the caller information.
> >
> > caller_id bitmap:
> > [63:32] thread_id
> > [31]    flags of in thread context
> > [30:0]  processor id
>
> The primary purpose of @caller_id is so that the printk-subsystem can
> coordinate LOG_CONT messages.
>
> Your patch is about logging/printing additional context attributes of
> the printk-caller. This is something we have discussed before [0]. I
> think this should be addressed at some point. But we need to come up
> with a solution that is flexible and generic. We should not be touching
> these core structures every time some new attribute needs to be printed.
>
> Also, this patch is controversial for other reasons:
>
> - it adds bitwise logic, when it could more easily just add a new field
>   (for example, caller_cpu)
>
> - it increases the size of all records by 4 bytes
>
> - it changes the internal structure in a way that breaks existing crash
>   tools
>
> - for non-task contexts, the increased size is wasted
>
> John Ogness
>
> [0] https://lore.kernel.org/lkml/20200904082438.20707-1-changki.kim@samsung.com