From: Michael Ellerman <mpe@ellerman.id.au>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Petr Mladek <pmladek@suse.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
syzkaller <syzkaller@googlegroups.com>
Subject: Re: [PATCH] printk: Add caller information to printk() output.
Date: Thu, 21 Mar 2019 13:59:53 +1100 [thread overview]
Message-ID: <871s312aqe.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <93f19e57-5051-c67d-9af4-b17624062d44@i-love.sakura.ne.jp>
Hi Tetsuo,
Thanks for implementing this, it's really helpful.
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> writes:
...
> From 91f85d2bd494df2f73c605d8b4747e8cc0a61ae2 Mon Sep 17 00:00:00 2001
> From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Date: Tue, 18 Dec 2018 05:53:04 +0900
> Subject: [PATCH] printk: Add caller information to printk() output.
>
> Sometimes we want to print a series of printk() messages to consoles
> without being disturbed by concurrent printk() from interrupts and/or
> other threads. But we can't enforce printk() callers to use their local
> buffers because we need to ask them to make too much changes. Also, even
> buffering up to one line inside printk() might cause failing to emit
> an important clue under critical situation.
>
> Therefore, instead of trying to help buffering, let's try to help
> reconstructing messages by saving caller information as of calling
> log_store() and adding it as "[T$thread_id]" or "[C$processor_id]"
> upon printing to consoles.
>
> Some examples for console output:
>
> [ 1.222773][ T1] x86: Booting SMP configuration:
> [ 2.779635][ T1] pci 0000:00:01.0: PCI bridge to [bus 01]
> [ 5.069193][ T268] Fusion MPT base driver 3.04.20
> [ 9.316504][ C2] random: fast init done
> [ 13.413336][ T3355] Initialized host personality
>
> Some examples for /dev/kmsg output:
>
> 6,496,1222773,-,caller=T1;x86: Booting SMP configuration:
> 6,968,2779635,-,caller=T1;pci 0000:00:01.0: PCI bridge to [bus 01]
> SUBSYSTEM=pci
> DEVICE=+pci:0000:00:01.0
> 6,1353,5069193,-,caller=T268;Fusion MPT base driver 3.04.20
> 5,1526,9316504,-,caller=C2;random: fast init done
> 6,1575,13413336,-,caller=T3355;Initialized host personality
>
> Note that this patch changes max length of messages which can be printed
> by printk() or written to /dev/kmsg interface from 992 bytes to 976 bytes,
> based on an assumption that userspace won't try to write messages hitting
> that border line to /dev/kmsg interface.
Do you have any plans to update dmesg or other userspace tools to show
the caller information?
cheers
next prev parent reply other threads:[~2019-03-21 3:00 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-24 7:37 [PATCH] printk: Add caller information to printk() output Tetsuo Handa
2018-11-30 15:40 ` Petr Mladek
2018-12-01 14:44 ` Tetsuo Handa
2018-12-02 11:23 ` Tetsuo Handa
2018-12-04 2:02 ` Sergey Senozhatsky
2018-12-04 10:16 ` Tetsuo Handa
2018-12-04 10:38 ` Sergey Senozhatsky
2018-12-04 15:31 ` Petr Mladek
2018-12-03 15:06 ` Petr Mladek
2018-12-03 21:10 ` Tetsuo Handa
2018-12-04 15:27 ` Petr Mladek
2018-12-05 10:42 ` Tetsuo Handa
2018-12-05 11:50 ` Sergey Senozhatsky
2018-12-07 4:58 ` Tetsuo Handa
2018-12-07 5:31 ` Sergey Senozhatsky
2018-12-10 13:09 ` Petr Mladek
2018-12-10 14:01 ` Tetsuo Handa
2018-12-11 10:26 ` Tetsuo Handa
2018-12-12 2:25 ` Sergey Senozhatsky
2018-12-12 2:29 ` Sergey Senozhatsky
2018-12-13 12:18 ` Petr Mladek
2018-12-13 12:42 ` Sergey Senozhatsky
2018-12-17 14:54 ` Petr Mladek
2018-12-17 15:40 ` Sergey Senozhatsky
2018-12-17 21:05 ` Tetsuo Handa
2018-12-18 8:39 ` Petr Mladek
2018-12-18 8:58 ` Sergey Senozhatsky
2019-01-02 16:09 ` Dmitry Vyukov
2019-01-03 18:27 ` Dmitry Vyukov
2019-01-04 7:33 ` Fengguang Wu
2019-01-11 19:34 ` Kevin Hilman
2019-01-10 11:27 ` Tetsuo Handa
2018-12-18 8:55 ` Sergey Senozhatsky
2018-12-18 10:01 ` Petr Mladek
2018-12-18 10:10 ` Sergey Senozhatsky
2019-03-21 2:59 ` Michael Ellerman [this message]
2019-03-21 10:20 ` Petr Mladek
2019-03-22 0:48 ` Michael Ellerman
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