From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Pavel Machek <pavel@ucw.cz>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Jan Kara <jack@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Jan Kara <jack@suse.com>, Petr Mladek <pmladek@suse.com>,
Tejun Heo <tj@kernel.org>,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
linux-kernel@vger.kernel.org,
Byungchul Park <byungchul.park@lge.com>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: [RFC][PATCH v6 0/2] printk: Make printk() completely async
Date: Mon, 25 Apr 2016 00:00:15 +0900 [thread overview]
Message-ID: <20160424150015.GA620@swordfish> (raw)
In-Reply-To: <20160424133522.GA1181@amd>
On (04/24/16 15:35), Pavel Machek wrote:
[..]
> > > So... from basically linux 0.0, cli() printk("") could be used for
> > > debugging. ... and that's now gone. Right?
> > >
> > > Can you explain why that is good idea?
> >
> > it's not gone. you need to explicitly enable async printk mode. the case
> > you mentioned -- cli() printk("")->console_unlock() -- apart from being
> > useful in some scenarios, can cause problems in others, simply because
> > under some circumstances it can run forever, as long as there are printk()
> > calls coming from other CPUs (which can happen during, f.e., debugging).
> > did you mean UP systems? well, async printk is sort of useless on UP systems
> > anyway.
>
> Well, yes, it has been long known that printk() can take long
> time.. Still that's not a problem for smaller system.
well, embedded systems can have slow serial consoles (so
console_unlock()->call_consoles_drivers() endup in uart/etc
device driver). and small systems are the systems where I
see problems with printk.
> Now, patch set above says "Make printk() completely async" -- so I
> assumed that it does...
that's my bad, sorry. I didn't keep an eye on the cover letter
(except for the changelog).
-ss
prev parent reply other threads:[~2016-04-24 14:02 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-21 17:25 [RFC][PATCH v6 0/2] printk: Make printk() completely async Sergey Senozhatsky
2016-03-21 17:25 ` [RFC][PATCH v6 1/2] " Sergey Senozhatsky
2016-03-22 13:11 ` Petr Mladek
2016-03-22 14:04 ` Petr Mladek
2016-03-23 0:37 ` Sergey Senozhatsky
2016-03-23 8:42 ` Sergey Senozhatsky
2016-03-23 10:04 ` Petr Mladek
2016-03-24 2:24 ` Sergey Senozhatsky
2016-03-22 16:36 ` Petr Mladek
2016-03-23 1:24 ` Sergey Senozhatsky
2016-03-23 9:25 ` Petr Mladek
2016-03-23 13:20 ` Jan Kara
2016-03-23 14:30 ` Sergey Senozhatsky
2016-03-23 14:41 ` Jan Kara
2016-03-21 17:25 ` [RFC][PATCH v6 2/2] printk: Make wake_up_klogd_work_func() async Sergey Senozhatsky
2016-03-22 6:49 ` [RFC][PATCH v6 0/2] printk: Make printk() completely async Jan Kara
2016-03-22 7:57 ` Sergey Senozhatsky
2016-03-22 8:15 ` Jan Kara
2016-04-23 19:40 ` Pavel Machek
2016-04-24 5:14 ` Sergey Senozhatsky
2016-04-24 13:35 ` Pavel Machek
2016-04-24 15:00 ` Sergey Senozhatsky [this message]
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