From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Petr Mladek <pmladek@suse.com>,
Sergey Senozhatsky <sergey.senozhatsky@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, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH 3/3] lockdep: Use line-buffered printk() for lockdep messages.
Date: Fri, 9 Nov 2018 15:12:04 +0900 [thread overview]
Message-ID: <20181109061204.GC599@jagdpanzerIV> (raw)
In-Reply-To: <9648a384-853c-942e-6a8d-80432d943aae@i-love.sakura.ne.jp>
On (11/08/18 20:37), Tetsuo Handa wrote:
> On 2018/11/08 13:45, Sergey Senozhatsky wrote:
> > So, can we just do the following? /* a sketch */
> >
> > lockdep.c
> > printk_safe_enter_irqsave(flags);
> > lockdep_report();
> > printk_safe_exit_irqrestore(flags);
>
> If buffer size were large enough to hold messages from out_of_memory(),
> I would like to use it for out_of_memory() because delaying SIGKILL
> due to waiting for printk() to complete is not good. Surely we can't
> hold all messages because amount from dump_tasks() is unpredictable.
> Maybe we can hold all messages from dump_header() except dump_tasks().
>
> But isn't it essentially same with
> http://lkml.kernel.org/r/1493560477-3016-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp
> which Linus does not want?
Dunno. I guess we still haven't heard from Linus because he did quite a good
job setting up his 'email filters' ;)
Converting the existing users to buffered printk is not so simple.
Apparently there are different paths; some can afford buffered printk, some
cannot. Some of 'cont' users tend to get advantage of transparent 'cont'
context: start 'cont' output in function A: A()->pr_cont(), continue it in
B: A()->B()->pr_cont(), and then in C: A()->B()->C()->pr_cont(), and
finally flush in A: A()->pr_cont(\n). And then some paths have the
early_printk requirement. We can break the 'transparent cont' by passing
buffer pointers around [it can get a bit hairy; looking at lockdep patch],
but early_printk requirement is a different beast.
So in my email I was not advertising printk_safe as a "buffered printk for
everyone", I was just talking about lockdep. It's a bit doubtful that Peter
will ACK lockdep transition to buffered printk.
-ss
next prev parent reply other threads:[~2018-11-09 6:12 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 [this message]
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
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
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