linux-kernel - Re: [RFC PATCH v1 16/25] printk: implement CON

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Date:   Tue, 26 Feb 2019 16:38:14 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Daniel Wang <wonderfly@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        Jiri Slaby <jslaby@...e.com>,
        Peter Feiner <pfeiner@...gle.com>,
        linux-serial@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [RFC PATCH v1 16/25] printk: implement CON_PRINTBUFFER

On Tue 2019-02-12 15:29:54, John Ogness wrote:
> If the CON_PRINTBUFFER flag is not set, do not replay the history
> for that console.

This patch fixes a regression caused by previous patches.
We need to do it a way that does not cause the regression
and do not break bisection.

> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 6c875abd7b17..b97d4195b09a 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -1596,8 +1592,12 @@ static void call_console_drivers(u64 seq, const char *ext_text, size_t ext_len,
>  		if (!(con->flags & CON_ENABLED))
>  			continue;
>  		if (!con->wrote_history) {
> -			printk_write_history(con, seq);
> -			continue;
> +			if (con->flags & CON_PRINTBUFFER) {
> +				printk_write_history(con, seq);
> +				continue;
> +			}
> +			con->wrote_history = 1;

I have just got an idea that we do not need a new flag.
We could clear CON_PRINTBUFFER bit instead.

Best Regards,
Petr