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From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	John Ogness <john.ogness@linutronix.de>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Prarit Bhargava <prarit@redhat.com>,
	Mark Salyzyn <salyzyn@android.com>,
	Chunyan Zhang <zhang.lyra@gmail.com>,
	Orson Zhai <orsonzhai@gmail.com>,
	Changki Kim <changki.kim@samsung.com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC 2/2] printk: Add more information about the printk caller
Date: Thu, 24 Sep 2020 10:40:10 +0900	[thread overview]
Message-ID: <20200924014010.GB577@jagdpanzerIV.localdomain> (raw)
In-Reply-To: <20200923135617.27149-3-pmladek@suse.com>

On (20/09/23 15:56), Petr Mladek wrote:
> The information about the printk caller has been added by the commit
> 15ff2069cb7f967da ("printk: Add caller information to printk() output.").
> The main motivation was to reconstruct original messages when they
> longer output from different CPUs got mixed.
> 
> But there are more usecases. The number of CPUs and tasks running on
> a single system is growing. It brings bigger challenges when debugging
> problems. The context in which kernel reports its state is sometimes
> pretty useful.
> 
> In particular, people suggest to remember the task id, cpu id, more details
> about the interrupt context, and even the task name [0][1].
> 
> Prepare for extending the caller information by replacing caller_id
> with struct printk_caller. And always store task id, cpu id, and
> exact interrupt context.

Wild idea:

Currently, we have two sides to the problem, I think. There are tasks
that store messages, but then there are tasks that print those messages
on the consoles. And those tasks and contexts are not always the same.
What I found helpful in the past was not only the caller_id, but the
emitter_id (especially preemption count and irqs state of the context
that prints messages on the slow consoles).

	-ss

  reply	other threads:[~2020-09-24  1:40 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-23 13:56 [RFC 0/2] printk: Add more metadata for each record Petr Mladek
2020-09-23 13:56 ` [PATCH 1/2] printk: Store all three timestamps Petr Mladek
2020-09-23 22:12   ` John Ogness
2020-09-24  1:45     ` Sergey Senozhatsky
2020-09-24 11:49     ` Petr Mladek
     [not found]       ` <CAJ-C09hqwOJhSXx1h40q96xhNZFXxP6dUVfjUQZpO4ZhOMZLbQ@mail.gmail.com>
2020-09-25  9:51         ` Petr Mladek
2020-09-24  0:00   ` John Ogness
2020-09-24 10:37     ` Petr Mladek
2020-09-23 13:56 ` [RFC 2/2] printk: Add more information about the printk caller Petr Mladek
2020-09-24  1:40   ` Sergey Senozhatsky [this message]
2020-09-24 11:58     ` Petr Mladek
2020-09-24  2:17   ` Sergey Senozhatsky
2020-09-24  8:23     ` John Ogness
2020-09-24 13:26       ` Petr Mladek
2020-09-24 13:06     ` Petr Mladek
2020-09-24  4:24   ` Ahmed S. Darwish
2020-09-24 12:53     ` Petr Mladek
2020-09-24 13:38       ` Petr Mladek
2020-09-25  0:54         ` Sergey Senozhatsky
2020-09-25 10:20           ` Petr Mladek
2020-10-21 11:48   ` 김창기

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