From: Petr Mladek <pmladek@suse.com>
To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: 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 13:58:14 +0200 [thread overview]
Message-ID: <20200924115814.GB29288@alley> (raw)
In-Reply-To: <20200924014010.GB577@jagdpanzerIV.localdomain>
On Thu 2020-09-24 10:40:10, Sergey Senozhatsky wrote:
> 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).
Yeah, it might be useful. But it should get discussed in a separate thread.
The information about the emitter do not need to get stored into the
metadata. It is mostly need only for debugging printk-related
problems. It should become less important if we succeed with
introducing the printk kthreads.
Best Regards,
Petr
next prev parent reply other threads:[~2020-09-24 11:58 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
2020-09-24 11:58 ` Petr Mladek [this message]
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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