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Date: Wed, 23 Mar 2016 23:30:20 +0900
From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Jan Kara <jack@suse.cz>
Cc: Petr Mladek <pmladek@suse.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>, Jan Kara <jack@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>
Subject: Re: [RFC][PATCH v6 1/2] printk: Make printk() completely async
Message-ID: <20160323143020.GA596@swordfish>
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Hello,

On (03/23/16 14:20), Jan Kara wrote:
[..]
> > I though that it actually could be an advantage. console_verbore() is
> > called also by oops_begin() and it does not need to be fatal. But you
> > are right that it does not need to be the righ approach.
> 
> If we oops, I want printk to be sync regardless whether the machine is able
> to live afterwards or not. You never know in advance... That's why I've
> chosen the console_verbose() trigger and I still think it is better than
> oops_in_progress or special console_panic() trigger.

console_verbose() is good enough. well, with special console_panic() trigger
we can have better control and distinguish between "print a lot" and "things
are bad for sure, print in sync mode". there are 2 archs that call console_verbose()
in setup_arch():

- arch/microblaze/kernel/setup.c

: void __init setup_arch(char **cmdline_p)
: {
:         *cmdline_p = boot_command_line;
: 
:         console_verbose();			<<<<
: 
:         unflatten_device_tree();
: 
:         setup_cpuinfo();
: 
:         microblaze_cache_init();
: 
:         setup_memory();

- arch/nios2/kernel/setup.c

: void __init setup_arch(char **cmdline_p)
: {
:         int bootmap_size;
: 
:         console_verbose();			<<<<
: 
: #ifdef CONFIG_EARLY_PRINTK
:         setup_early_printk();
: #endif


so printk will never work in async mode there. hm... should we care?

	-ss