Hi Greg.
This still needs a small fix, see below.
Am 03.11.2012 22:12, schrieb Jan H. Schönherr:
> From: Jan H. Schönherr <schn...@cs.tu-berlin.de>
>
> The meaning of LOG_CONT is unclear, i. e., whether a message is a starting,
> ending, or middle fragment. Unfortunately, this cannot be inferred from
> the LOG_PREFIX and LOG_NEWLINE flags, as they are not always kept.
> Furthermore, in some cases LOG_CONT is set, although it is unknown if
> there will be a continuation. This leads to wrongly concatenated output.
>
> Fix this by dropping LOG_CONT and rely on LOG_PREFIX and LOG_NEWLINE to
> distinguish the type of fragment. That is, if LOG_PREFIX is set, this
> fragment does not continue the previous fragment. And if LOG_NEWLINE is
> set, this fragment is not continued by the next fragment.
>
> (Unfortunately, we still have to look at the previous fragment to catch the
> case of an unset LOG_PREFIX on this fragment, but a set LOG_NEWLINE on
> the previous fragment.)
>
> Tested-By: Kay Sievers <k...@vrfy.org>
> Signed-off-by: Jan H. Schönherr <schn...@cs.tu-berlin.de>
> ---
> Against linux-next from 20121102, added Kay's tested-by.
> ---
> kernel/printk.c | 57
> +++++++++++++++++++++++++++++++++------------------------
> 1 file changed, 33 insertions(+), 24 deletions(-)
>
> diff --git a/kernel/printk.c b/kernel/printk.c
> index 22e070f..e8e4e67 100644
> --- a/kernel/printk.c
> +++ b/kernel/printk.c
[...]
> @@ -1581,12 +1585,16 @@ asmlinkage int vprintk_emit(int facility, int level,
> * Flush the conflicting buffer. An earlier newline was missing,
> * or another task also prints continuation lines.
> */
> - if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
> - cont_flush(LOG_NEWLINE);
> + if (cont.len) {
This line should have been:
+ if (cont.len && !cont.flushed) {
The effect of this is that we now avoid to add a superfluous newline
over and over (due to setting LOG_PREFIX), when the cont buffer has been
flushed but not yet printed.
> + if (cont.owner != current)
> + lflags |= LOG_PREFIX;
> + if (lflags & LOG_PREFIX)
> + cont_flush(LOG_NEWLINE);
> + }
>
> /* buffer line if possible, otherwise store it right away */
> - if (!cont_add(facility, level, text, text_len))
> - log_store(facility, level, lflags | LOG_CONT, 0,
> + if (!cont_add(facility, level, lflags, text, text_len))
> + log_store(facility, level, lflags, 0,
> dict, dictlen, text, text_len);
> } else {
> bool stored = false;
> @@ -1599,7 +1607,8 @@ asmlinkage int vprintk_emit(int facility, int level,
> */
> if (cont.len && cont.owner == current) {
For symmetry reasons, the "if" here could use the same change. But here it
does not really matter as currently cont_add() and cont_flush() are NOPs when
cont.flushed is set.
> if (!(lflags & LOG_PREFIX))
> - stored = cont_add(facility, level, text,
> text_len);
> + stored = cont_add(facility, level, lflags,
> + text, text_len);
> cont_flush(LOG_NEWLINE);
> }
As I've not yet seen this patch turn up anywhere, I'm preparing a v2 of this
together with a couple of other patches that are now more or less ready.
Regards
Jan
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