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From: Andrew Morton <akpm@linux-foundation.org>
To: Jan Kara <jack@suse.cz>
Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>,
	LKML <linux-kernel@vger.kernel.org>,
	pmladek@suse.cz, Frederic Weisbecker <fweisbec@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 8/8] printk: Add config option for disabling printk offloading
Date: Wed, 23 Apr 2014 11:17:50 -0700	[thread overview]
Message-ID: <20140423111750.88ad799bb271a1fe0bed119f@linux-foundation.org> (raw)
In-Reply-To: <20140423110847.GB17824@quack.suse.cz>

On Wed, 23 Apr 2014 13:08:47 +0200 Jan Kara <jack@suse.cz> wrote:

> > If you want reliable crash logging then we need to be able to set a
> > printk level mask per console and just set the serial console for
> > "crit/err" and the queue console for the rest, with a 'cat
> > >/dev/ttywhatever' running if this feature was in use ?
>   Ok, now I understand. Thanks for an interesting idea. IMO people
> definitely need messages logged directly into serial console when e.g. oops
> is happening because very likely they won't get logged to disk and even
> userspace won't have a chance to run and copy messages to the serial
> console. Plus for useful softlockup reports or oops messages you need also
> the KERN_NOTICE and KERN_INFO messages - stack traces, cpu numbers, process
> information - all this is printed with these levels.
> 
> These obvious places could be changed to print with lower log level I
> assume but still I'm somewhat worried that some KERN_INFO messages that
> would be useful for debugging a crash won't make it to console before the
> crash happens.
> 
> But if both you and Andrew think that the above problems are smaller than
> the complexity connected with printk offloading, I can give it a try.
> Andrew?

I'm curious about the idea of writing a new(?) console driver which the
problematic machines can use.

The problem of course will be in sizing the driver's queue.  Perhaps we
can have a driver which uses a huge queue, temporarily use that driver
during boot then switch over to a conventional console driver?


  parent reply	other threads:[~2014-04-23 18:17 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-03-25 17:54 [PATCH 0/8 v4] printk: Cleanups and softlockup avoidance Jan Kara
2014-03-25 17:54 ` [PATCH 1/8] printk: Remove outdated comment Jan Kara
2014-03-25 17:54 ` [PATCH 2/8] printk: Release lockbuf_lock before calling console_trylock_for_printk() Jan Kara
2014-04-23 20:56   ` Andrew Morton
2014-04-24 10:18     ` Jan Kara
2014-03-25 17:54 ` [PATCH 3/8] printk: Enable interrupts " Jan Kara
2014-03-25 17:54 ` [PATCH 4/8] printk: Remove separate printk_sched buffers and use printk buf instead Jan Kara
2014-05-05 18:37   ` Steven Rostedt
2014-03-25 17:54 ` [PATCH 5/8] printk: Hand over printing to console if printing too long Jan Kara
2014-03-25 17:54 ` [PATCH 6/8] printk: Start printing handover kthreads on demand Jan Kara
2014-03-26 17:16   ` One Thousand Gnomes
2014-03-26 19:06     ` Jan Kara
2014-03-25 17:55 ` [PATCH 7/8] kernel: Avoid softlockups in stop_machine() during heavy printing Jan Kara
2014-03-25 17:55 ` [PATCH 8/8] printk: Add config option for disabling printk offloading Jan Kara
2014-03-26 17:23   ` One Thousand Gnomes
2014-03-26 19:28     ` Jan Kara
2014-04-18 18:54       ` Andrew Morton
2014-04-22 10:22         ` One Thousand Gnomes
2014-04-23 11:08           ` Jan Kara
2014-04-23 12:35             ` One Thousand Gnomes
2014-04-23 14:29               ` Jan Kara
2014-04-23 18:17             ` Andrew Morton [this message]
2014-04-23 21:16               ` One Thousand Gnomes
2014-04-23 21:41                 ` Jiri Kosina
2014-04-24 14:00                   ` One Thousand Gnomes
2014-05-15 21:28               ` Jan Kara
2014-04-23  9:30         ` Jan Kara
2014-04-08 14:27 ` [PATCH 0/8 v4] printk: Cleanups and softlockup avoidance Jan Kara
2014-04-08 19:02   ` Andrew Morton
  -- strict thread matches above, loose matches on Subject: below --
2014-03-14 16:21 [PATCH 0/8 v3] " Jan Kara
2014-03-14 16:21 ` [PATCH 8/8] printk: Add config option for disabling printk offloading Jan Kara

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