linux-kernel - Re: [PATCH v8 3/3] printk: fix double printing with earlycon

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Message-ID: <20170330055546.GD513@jagdpanzerIV.localdomain>
Date:   Thu, 30 Mar 2017 14:55:46 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Aleksey Makarov <aleksey.makarov@...aro.org>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sudeep Holla <sudeep.holla@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Hurley <peter@...leysoftware.com>,
        Jiri Slaby <jslaby@...e.com>,
        Robin Murphy <robin.murphy@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        "Nair, Jayachandran" <Jayachandran.Nair@...ium.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [PATCH v8 3/3] printk: fix double printing with earlycon

On (03/28/17 14:56), Petr Mladek wrote:
[..]
> > > Is it better?  If not, I will send a version with console_cmdline_last.
> > 
> > personally I'm fine with the nested loop. the latest version
> > 	"for (last = MAX_CMDLINECONSOLES - 1; last >= 0;..."
> > 
> > is even easier to read.
> 
> The number of elements is bumped on a single location, so there
> is not much to synchronize. The old approach was fine because
> the for cycles were needed anyway, they started on the 0th element,
> and NULL ended arrays are rather common practice.
> 
> But we are searching the array from the end now. Also we use the
> for cycle just to get the number here. This is not a common
> practice and it makes the code more complicated and strange from
> my point of view.

I'm fine with either way :)

[..]
> > neither add_preferred_console() nor __add_preferred_console() have any
> > serialization. and I assume that we can call add_preferred_console()
> > concurrently, can't we?
[..]
> If I did not miss anything, it would seem that
> __add_preferred_console() are called synchronously
> and only during boot by design.

thanks. I think you are right. it's console_initcall or __init.

	-ss