linux-kernel - Re: [PATCH v3 3/7] printk: LOG_CONT and LOG

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Date:	Fri, 18 Jul 2014 14:34:57 -0500
From:	Alex Elder <elder@...aro.org>
To:	akpm@...ux-foundation.org
CC:	kay@...y.org, pmladek@...e.cz, bp@...e.de, john.stultz@...aro.org,
	jack@...e.cz, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/7] printk: LOG_CONT and LOG_NEWLINE are opposites

On 07/18/2014 09:14 AM, Alex Elder wrote:
> Two log record flags--LOG_CONT and LOG_NEWLINE--are mutually
> exclusive.  That is, one or the other is always set, but they are
> never both set at the same time in a log record flags field.  What
> follows is a great deal of explanation that aims to prove this
> assertion.
> 
> Having that knowledge allows us to simplify a bit of logic, and with
> a little more work (in follow-on patches) it allows us to do without
> some flag values, considerably simplifying things.

And in this patch I inadvertently deleted a hunk.  It
goes at the end, and I've appended it below.

I'm really sorry I screwed these patches up.  I got
sloppy, and tried to send them out in a hurry this
morning.

I'm going to post a new version 4 that will correct these
things.

					-Alex

> Signed-off-by: Alex Elder <elder@...aro.org>
> Reviewed-by: Petr Mládek <pmladek@...e.cz>
> ---
>  kernel/printk/printk.c | 18 +++++++++++-------
>  1 file changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index f2a069e..00367b5 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -1006,11 +1006,9 @@ static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
>  		prefix = false;
>  
>  	if (msg->flags & LOG_CONT) {
> -		if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
> +		if (prev & LOG_CONT)
>  			prefix = false;
> -
> -		if (!(msg->flags & LOG_NEWLINE))
> -			newline = false;
> +		newline = false;
>  	}
>  
>  	do {
> @@ -1639,10 +1637,16 @@ asmlinkage int vprintk_emit(int facility, int level,
>  	text_len += vscnprintf(text + text_len,
>  			       sizeof(textbuf) - text_len, fmt, args);
>  
> -	/* mark and strip a trailing newline */
> +	/*
> +	 * If there's a trailing newline, flag it and strip it off.
> +	 * Otherwise we assume this is a partial log message, to be
> +	 * continued with the next call.
> +	 */
>  	if (text_len && text[text_len-1] == '\n') {
>  		text_len--;
> -		lflags |= LOG_NEWLINE;
> +		lflags = LOG_NEWLINE;
> +	} else {
> +		lflags = LOG_CONT;
>  	}
>  
>  	/* strip kernel syslog prefix and extract log level or control flags */
> @@ -1672,7 +1676,7 @@ asmlinkage int vprintk_emit(int facility, int level,
>  		level = default_message_loglevel;
>  
>  	if (dict)
> -		lflags |= LOG_PREFIX|LOG_NEWLINE;
> +		lflags = LOG_PREFIX|LOG_NEWLINE;
>  
>  	if (!(lflags & LOG_NEWLINE)) {
>  		/*
> 
@@ -1700,8 +1700,7 @@ asmlinkage int vprintk_emit(int facility
                if (cont_add(facility, level, text, text_len))
                        printed_len += text_len;
                else
-                       printed_len += log_store(facility, level,
-                                                lflags | LOG_CONT, 0,
+                       printed_len += log_store(facility, level, lflags, 0,
                                                 dict, dictlen, text,
text_len);
        } else {
                bool stored = false;

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