From: Dmitry Safonov <dima@arista.com>
To: Petr Mladek <pmladek@suse.com>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: linux-kernel@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jslaby@suse.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Subject: Re: [RFC] printk/sysrq: Don't play with console_loglevel
Date: Wed, 12 Jun 2019 15:47:38 +0100 [thread overview]
Message-ID: <34698b8a-5204-e9e8-b96b-dbb16340423d@arista.com> (raw)
In-Reply-To: <20190612120012.mmokgz4yybywfs26@pathway.suse.cz>
On 6/12/19 1:00 PM, Petr Mladek wrote:
> On Wed 2019-06-12 17:36:43, Sergey Senozhatsky wrote:
>> On (06/06/19 09:10), Petr Mladek wrote:
>>> Just to be sure. I wanted to say that I like the idea with
>>> KERN_UNSUPRESSED. So, I think that we are on the same page.
>>
>> I understand. All I wanted to say is that KERN_UNSUPRESSED is
>> per-message, while the most interesting (and actually broken)
>> cases, IMHO, are per-context, IOW things like this one
>>
>> console_loglevel = NEW
>> foo()
>> dump_stack()
>> printk
>> ...
>> printk
>> console_loglevel = OLD
>>
>> KERN_UNSUPRESSED does not help here. We probably can't convert
>> dump_stack() to KERN_UNSUPRESSED.
>
> I agree. I take KERN_UNSUPRESSED like a nice trick how to pass
> the information about the unsupressed printk context via
> printk_safe and printk_nmi per-CPU buffers.
>
> The single line in sysrq __handle_sysrq() seems to be the only
> location where KERN_UNSUPRESSED can be used directly.
I likely don't understand all the reasons why it's not possible.
Looking at kdb - prints those can't be converted straight-away are
show_regs() and show_stack().. could we add helpers those take a
loglevel to show the info? (having as an example show_trace_log_lvl()
that can "eat" a modifier already).
Not that I want to sell the idea of KERN_UNSUPRESSED, but to my mind the
alternative patches were kind of too intricate and bring more complexity
to printk.. and there are only ~3(?) places those manipulate
console_loglevel directly in the kernel tree (so we might want something
simple and dumb as hell).
Thanks,
Dima
prev parent reply other threads:[~2019-06-12 14:47 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-28 0:24 [RFC] printk/sysrq: Don't play with console_loglevel Dmitry Safonov
2019-05-28 3:21 ` Tetsuo Handa
2019-05-28 4:22 ` Sergey Senozhatsky
2019-05-28 8:02 ` Tetsuo Handa
2019-05-28 8:51 ` Sergey Senozhatsky
2019-05-28 10:15 ` Tetsuo Handa
2019-05-28 13:49 ` Petr Mladek
2019-06-07 17:09 ` Pavel Machek
2019-06-08 2:45 ` Tetsuo Handa
2019-06-11 15:10 ` Petr Mladek
2019-06-12 10:06 ` Tetsuo Handa
2019-05-28 4:15 ` Sergey Senozhatsky
2019-05-28 4:46 ` Sergey Senozhatsky
2019-05-28 13:42 ` Petr Mladek
2019-05-28 14:21 ` Tetsuo Handa
2019-05-28 15:03 ` Petr Mladek
2019-05-28 15:21 ` Tetsuo Handa
2019-05-28 15:58 ` Dmitry Safonov
2019-05-31 14:11 ` Tetsuo Handa
2019-06-02 6:13 ` [RFC] printk: Introduce per context console loglevel Tetsuo Handa
2019-06-06 7:59 ` Petr Mladek
2019-06-03 6:51 ` [RFC] printk/sysrq: Don't play with console_loglevel Sergey Senozhatsky
2019-06-06 7:10 ` Petr Mladek
2019-06-12 8:36 ` Sergey Senozhatsky
2019-06-12 12:00 ` Petr Mladek
2019-06-12 14:47 ` Dmitry Safonov [this message]
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