From: David Laight <David.Laight@ACULAB.COM>
To: 'Tetsuo Handa' <penguin-kernel@i-love.sakura.ne.jp>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Dmitriy Vyukov <dvyukov@google.com>,
Steven Rostedt <rostedt@goodmis.org>,
Alexander Potapenko <glider@google.com>,
Fengguang Wu <fengguang.wu@intel.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Will Deacon <will.deacon@arm.com>
Subject: RE: [PATCH v6 1/3] printk: Add line-buffered printk() API.
Date: Wed, 7 Nov 2018 11:01:05 +0000 [thread overview]
Message-ID: <8354d714f6b6489d9003d6e04ee10618@AcuMS.aculab.com> (raw)
In-Reply-To: <42f33aae-a1d1-197f-a1d5-8c5ec88e88d1@i-love.sakura.ne.jp>
From: Tetsuo Handa
> Sent: 07 November 2018 10:53
>
> On 2018/11/06 23:35, Sergey Senozhatsky wrote:
> >> Since we want to remove "struct cont" eventually, we will try to remove
> >> both "implicit printk() users who are expecting KERN_CONT behavior" and
> >> "explicit pr_cont()/printk(KERN_CONT) users". Therefore, converting to
> >> this API is recommended.
> >
> > - The printk-fallback sounds like a hint that the existing 'cont' handling
> > better stay in the kernel. I don't see how the existing 'cont' is
> > significantly worse than
> > bpr_warn(NULL, ...)->printk() // no 'cont' support
> > I don't see why would we want to do it, sorry. I don't see "it takes 16
> > printk-buffers to make a thing go right" as a sure thing.
>
> Existing 'cont' handling will stay for a while. After majority of
> pr_cont()/KERN_CONT users are converted, 'cont' support will be removed
> (e.g. KERN_CONT becomes "").
A though:
Why not make the printf lock slightly 'sticky'?
- If the output line is incomplete save the cpuid.
- If there is a saved cpuid that doesn't match the current cpu then spin for a bit.
Any callers of printk() have to assume they will spin on the buffer for the
longest printk formatting (and symbol lookup might take a while) so a short
additional delay won't matter.
Then two calls to printk() for the same line won't (usually) get split and
none of the callers need any changes.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2018-11-07 11:01 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-02 13:31 [PATCH v6 1/3] printk: Add line-buffered printk() API Tetsuo Handa
2018-11-02 13:31 ` [PATCH 2/3] mm: Use line-buffered printk() for show_free_areas() Tetsuo Handa
2018-11-07 14:07 ` Petr Mladek
2018-11-02 13:31 ` [PATCH 3/3] lockdep: Use line-buffered printk() for lockdep messages Tetsuo Handa
2018-11-02 13:36 ` Peter Zijlstra
2018-11-03 2:00 ` Tetsuo Handa
2018-11-06 8:38 ` Petr Mladek
2018-11-06 9:05 ` Sergey Senozhatsky
2018-11-06 12:57 ` Petr Mladek
2018-11-06 9:56 ` Tetsuo Handa
2018-11-07 15:19 ` Petr Mladek
2018-11-08 4:45 ` Sergey Senozhatsky
2018-11-08 11:37 ` Tetsuo Handa
2018-11-09 6:12 ` Sergey Senozhatsky
2018-11-09 9:55 ` Tetsuo Handa
2018-11-09 15:43 ` Petr Mladek
2018-11-10 2:42 ` Tetsuo Handa
2018-11-23 12:46 ` Petr Mladek
2018-11-23 13:12 ` Tetsuo Handa
2018-11-23 15:56 ` Steven Rostedt
2018-11-24 0:24 ` Tetsuo Handa
2018-11-26 4:34 ` Sergey Senozhatsky
2018-11-28 13:29 ` David Laight
2018-11-29 10:09 ` Tetsuo Handa
2018-11-30 16:01 ` Petr Mladek
2018-11-10 8:52 ` Tetsuo Handa
2018-11-23 12:52 ` Petr Mladek
2018-11-09 14:08 ` Linus Torvalds
2018-11-09 14:42 ` Steven Rostedt
2018-11-08 11:53 ` Petr Mladek
2018-11-08 12:44 ` Sergey Senozhatsky
2018-11-08 14:21 ` Sergey Senozhatsky
2018-11-09 9:54 ` Tetsuo Handa
2018-11-02 14:40 ` [PATCH v6 1/3] printk: Add line-buffered printk() API Matthew Wilcox
2018-11-03 1:55 ` Tetsuo Handa
2018-11-02 18:12 ` kbuild test robot
2018-11-06 14:35 ` Sergey Senozhatsky
2018-11-07 10:21 ` Petr Mladek
2018-11-07 12:54 ` Tetsuo Handa
2018-11-08 2:21 ` Sergey Senozhatsky
2018-11-08 11:24 ` Petr Mladek
2018-11-08 11:46 ` Tetsuo Handa
2018-11-08 12:30 ` Sergey Senozhatsky
2018-11-09 14:10 ` Petr Mladek
2018-11-12 7:59 ` Sergey Senozhatsky
2018-11-12 10:42 ` Tetsuo Handa
2018-11-17 10:14 ` Tetsuo Handa
2018-11-07 10:52 ` Tetsuo Handa
2018-11-07 11:01 ` David Laight [this message]
2018-11-07 12:00 ` Petr Mladek
2018-11-07 11:45 ` Petr Mladek
2018-11-08 2:30 ` Sergey Senozhatsky
2018-11-07 13:41 ` Petr Mladek
2018-11-07 14:06 ` Petr Mladek
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=8354d714f6b6489d9003d6e04ee10618@AcuMS.aculab.com \
--to=david.laight@aculab.com \
--cc=akpm@linux-foundation.org \
--cc=dvyukov@google.com \
--cc=fengguang.wu@intel.com \
--cc=glider@google.com \
--cc=jpoimboe@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mingo@redhat.com \
--cc=penguin-kernel@i-love.sakura.ne.jp \
--cc=peterz@infradead.org \
--cc=pmladek@suse.com \
--cc=rostedt@goodmis.org \
--cc=sergey.senozhatsky.work@gmail.com \
--cc=sergey.senozhatsky@gmail.com \
--cc=torvalds@linux-foundation.org \
--cc=will.deacon@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).