From: Petr Mladek <pmladek@suse.com>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Dmitry Safonov <dima@arista.com>,
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>
Subject: Re: [RFC] printk/sysrq: Don't play with console_loglevel
Date: Tue, 28 May 2019 17:03:45 +0200 [thread overview]
Message-ID: <20190528150345.di2knfzmqfbwro3y@pathway.suse.cz> (raw)
In-Reply-To: <e564ee00-6a93-defd-4eab-e306bbfe8b01@i-love.sakura.ne.jp>
On Tue 2019-05-28 23:21:17, Tetsuo Handa wrote:
> On 2019/05/28 22:42, Petr Mladek wrote:
> >> Ahh.. OK, now I sort of remember why I gave up on this idea (see [1]
> >> at the bottom, when it comes to uv_nmi_dump_state()) - printk_NMI and
> >> printk-safe redirections.
> >>
> >> NMI
> >> loglevel = NEW
> >> printk -> printk_safe_nmi
> >> loglevel = OLD
> >>
> >> iret
> >>
> >> IRQ
> >> flush printk_safe_nmi -> printk
> >> // At this point we don't remember about
> >> // loglevel manipulation anymore
> >> iret
> >
> > printk_safe buffer preserves KERN_* headers. It should be
> > possible to insert KERN_UNSUPPRESSED there.
>
> But is context dependent buffer large enough to hold SysRq-t output?
> I think that only main logbuf can become large enough to hold SysRq-t output.
SysRq messages are stored directly into the main log buffer.
The limited per-CPU buffers are needed only in printk_safe
and NMI context. We discussed it here because KERN_UNSUPPRESSED
allows to pass the information even from this context.
> We can add KERN_UNSUPPRESSED to SysRq's header line. But I don't think
> that we can automatically add KERN_UNSUPPRESSED to SysRq's body lines
> based on some context information. If we want to avoid manipulating
> console_loglevel, we need to think about how to make sure that
> KERN_UNSUPPRESSED is added to all lines from such context without
> overflowing capacity of that buffer.
We could set this context in printk_context per-CPU variable.
Then we could easily add the set per-message flag in
vprintk_store() for the normal/atomic context. And we
could store an extra KERN_UNSUPPRESSED in printk_safe_log_store()
for printk_safe and NMI context.
Best Regards,
Petr
next prev parent reply other threads:[~2019-05-28 15:04 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 [this message]
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
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