linux-kernel - Re: Patch 0727d35de ("Make initramfs honor CONFIG_DEVTMPFS

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Date:   Tue, 12 Sep 2017 21:45:58 -0500
From:   Rob Landley <rob@...dley.net>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Yury Norov <ynorov@...iumnetworks.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Prarit Bhargava <prarit@...hat.com>,
        Yang Shi <yang.shi@...aro.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Kees Cook <keescook@...omium.org>,
        Emese Revfy <re.emese@...il.com>,
        Fabian Frederick <fabf@...net.be>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: Patch 0727d35de ("Make initramfs honor CONFIG_DEVTMPFS_MOUNT")
 breaks boot

On 09/11/2017 06:45 AM, Petr Mladek wrote:
>> Except for the second printk line: If you boot with rdinit=/bin/hush
>> then the first time you mount -t devtmpfs /dev /dev after boot (with
>> CONFIG_DEVTMPFS_MOUNT already having mounted it), you get the 0 return
>> value but the last printk() doesn't output? The second and later times
>> you repeat it, both printk() lines are output.
>>
>> What's up with printk?
>>
>> (I added the second printk because the _first_ one wasn't outputting
>> that first time. Something is happening to flush the printk() queue
>> instead of writing it out?
> 
> You need to add "\n" at the end of the line. Otherwise, it expects
> that the message would continue and puts it into a cont buffer.
> The buffer is flushed only when another non-continuous message
> is added.

Ah. The next one flushes the previous one, meaning when I repeat the
command I get the output I expected the second time but I'm seeing the
_previous_ instance of it, not the current one.

> This problem is more visible since the commit 5c2992ee7fd8a29d0412
> ("printk: remove console flushing special cases for partial buffered
> lines").

Gotcha. My bad.

Thanks,

Rob