From: Dmitry Safonov <0x7f454c46@gmail.com>
To: Russell King - ARM Linux admin <linux@armlinux.org.uk>,
Dmitry Safonov <dima@arista.com>
Cc: Juri Lelli <juri.lelli@redhat.com>,
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Subject: Re: [PATCH 00/50] Add log level to show_stack()
Date: Fri, 8 Nov 2019 21:08:30 +0000 [thread overview]
Message-ID: <5a411348-be84-f592-ef2d-ffaec99332bd@gmail.com> (raw)
In-Reply-To: <20191108173045.GY25745@shell.armlinux.org.uk>
On 11/8/19 5:30 PM, Russell King - ARM Linux admin wrote:
> On Fri, Nov 08, 2019 at 04:28:30PM +0000, Dmitry Safonov wrote:
[..]
>>
>> Well, the use-case for lower log-level is that everything goes into logs
>> (/var/log/dmesg or /var/log/messages whatever rsyslog has settting).
>>
>> That has it's value:
>> - after a failure (i.e. panic) messages, those were only signs that
>> something goes wrong can be seen in logs which can give ideas what has
>> happened.
>
> No they don't. When the kernel panics, userspace generally stops
> running, so rsyslog won't be able to write them to /var/log/messages.
>
> How, by "kernel panics" I mean a real kernel panic, which probably
> isn't what you're talking about there. You are probably talking
> about the whole shebang of non-fatal kernel oops, kernel warnings
> and the like. If so, I'd ask you to stop confuzzilating terminology.
>
> If you really want to capture such events, then you need to have the
> kernel write the panic to (e.g.) flash - see the mtdoops driver.
I was talking about things prior the panic: OOMs, MMC write/read
warnings, hung tasks, we also have local patches to produce a warning if
the mutex is being held for too long or a task is starving on CPU time
by hard/soft irqs (I hope I will design something like that for
upstream). I've found those warnings useful to:
(a) have an early message when the things are starting going bad.
(b) analyze contentions or too large scale for a box or faulty hardware
for non-reproducible issues just from logs.
We use kexec to save the dmesg ringbuffer content after the panic.
Thanks,
Dmitry
next prev parent reply other threads:[~2019-11-09 1:31 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-06 3:04 [PATCH 00/50] Add log level to show_stack() Dmitry Safonov
2019-11-06 3:05 ` [PATCH 26/50] powerpc: Add show_stack_loglvl() Dmitry Safonov
2019-11-06 9:52 ` Michael Ellerman
2019-11-06 16:01 ` Dmitry Safonov
2019-11-06 8:35 ` [PATCH 00/50] Add log level to show_stack() Petr Mladek
2019-11-06 16:12 ` Dmitry Safonov
2019-11-08 10:37 ` Sergey Senozhatsky
2019-11-08 13:04 ` Petr Mladek
2019-11-11 1:23 ` Sergey Senozhatsky
2019-11-11 9:12 ` Petr Mladek
2019-11-12 4:44 ` Sergey Senozhatsky
2019-11-12 4:57 ` Sergey Senozhatsky
2019-11-12 8:35 ` Petr Mladek
2019-11-12 10:12 ` Sergey Senozhatsky
2019-11-13 1:23 ` Sergey Senozhatsky
2019-11-13 2:25 ` Dmitry Safonov
2019-11-13 6:33 ` Sergey Senozhatsky
2019-11-13 8:47 ` Petr Mladek
2019-11-13 16:24 ` Steven Rostedt
2019-11-13 16:40 ` Dmitry Safonov
2019-11-15 0:50 ` Sergey Senozhatsky
2019-11-13 15:32 ` Steven Rostedt
2019-11-11 19:47 ` Dmitry Safonov
2019-11-12 2:17 ` Sergey Senozhatsky
2019-11-12 2:40 ` Dmitry Safonov
2019-11-12 4:25 ` Sergey Senozhatsky
2019-11-13 2:41 ` Dmitry Safonov
2019-11-13 2:51 ` Sergey Senozhatsky
2019-11-13 15:39 ` Steven Rostedt
2019-11-15 3:36 ` Sergey Senozhatsky
2019-11-06 9:20 ` Peter Zijlstra
2019-11-06 16:27 ` Dmitry Safonov
2019-11-06 20:34 ` Peter Zijlstra
2019-11-06 23:25 ` Russell King - ARM Linux admin
2019-11-13 15:44 ` Steven Rostedt
2019-11-08 16:28 ` Dmitry Safonov
2019-11-08 17:30 ` Russell King - ARM Linux admin
2019-11-08 21:08 ` Dmitry Safonov [this message]
2019-11-13 15:41 ` Steven Rostedt
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