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From: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Jan Kara <jack@suse.cz>, 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 22:16:09 +0100	[thread overview]
Message-ID: <20140423221609.0d3b536f@alan.etchedpixels.co.uk> (raw)
In-Reply-To: <20140423111750.88ad799bb271a1fe0bed119f@linux-foundation.org>

> 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?

It depends how early in boot you are but this is true equally of kernel
threads and other stuff.

The big problem doing it early is that we have no mechanism to "open" a
tty port without having a tty. We do now have the split for this for
queueing input and to some extent output, but not all of the "open"
aspect. The output buffering is also quite limited for most devices but
that bit *is* easy to fix if needed.

Given this all only affects huge boxes and the only fix we have right now
is hideously ugly I'd rather it stayed in the vendor hacks to their
trees, until someone is inspired to sort it properly.

On the plus side having a queueing console that can use tty methods would
mean you could make any tty a console and special hacks for support would
be improving reliability/early functionality rather than enabling.

Essentially you can create tty_port_kopen()/tty_port_kclose() and use
the tty device write methods with a tty_port, it's just a matter of
continuing to clean up the tty/tty_port split properly.

It's not a small job though.

Alan

  reply	other threads:[~2014-04-23 21:16 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2014-03-25 17:54 ` [PATCH 1/8] printk: Remove outdated comment Jan Kara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
2014-04-23 21:16               ` One Thousand Gnomes [this message]
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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