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References: <20210519063355.5147-1-ruifeng.zhang0110@gmail.com> <87v97ft9j7.fsf@jogness.linutronix.de>
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From:   Ruifeng Zhang <ruifeng.zhang0110@gmail.com>
Date:   Wed, 19 May 2021 17:24:48 +0800
Message-ID: <CAG7+-3OofjNSrpEjVVuUEH6G_f-QBqhda5P0bvfL4-eJYZgKHg@mail.gmail.com>
Subject: Re: [PATCH v1 1/1] printk: always output coreid in caller information
To:     John Ogness <john.ogness@linutronix.de>
Cc:     pmladek@suse.com, senozhatsky@chromium.org, rostedt@goodmis.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        ruifeng.zhang1@unisoc.com, nianfu.bai@unisoc.com,
        orson.zhai@unisoc.com
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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 prin=
tk.

Thanks.

Best regards,
Ruifeng

John Ogness <john.ogness@linutronix.de> =E4=BA=8E2021=E5=B9=B45=E6=9C=8819=
=E6=97=A5=E5=91=A8=E4=B8=89 =E4=B8=8B=E5=8D=884:25=E5=86=99=E9=81=93=EF=BC=
=9A
>
> Hello Ruifeng,
>
> On 2021-05-19, Ruifeng Zhang <ruifeng.zhang0110@gmail.com> wrote:
> > From: Ruifeng Zhang <ruifeng.zhang1@unisoc.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@samsu=
ng.com