On Tue, Nov 20, 2018 at 10:06:39PM +0100, Roland Hieber wrote:
> On Tue, Nov 20, 2018 at 09:50:44PM +0100, Roland Hieber wrote:
> > The levels of pr_emerg() and pr_cont() are both set to 0. When pr_cont()
> > is used to continue a previous line, and colored console output is
> > enabled, this can result in garbled log messages being printed, e.g.:
> >
> > ERROR: HABv4: -------- HAB warning Event 0 --------
> > ERROR: HABv4: event data:
> > ERROR: HABv4: dbEMERG: 00EMERG: 24EMERG: 42EMERG: 69EMERG: 30EMERG: e1EMERG: 1d
> > ERROR: HABv4: 00EMERG: 04EMERG: 00EMERG: 02EMERG: 40EMERG: 00EMERG: 36EMERG: 06
> > ERROR: HABv4: 55EMERG: 55EMERG: 00EMERG: 03EMERG: 00EMERG: 00EMERG: 00EMERG: 00
> > ERROR: HABv4: 00EMERG: 00EMERG: 00EMERG: 00EMERG: 00EMERG: 00EMERG: 00EMERG: 00
> > ERROR: HABv4: 00EMERG: 00EMERG: 00EMERG: 01EMERG:
> > ERROR: HABv4: Status: Operation completed with warning (0x69)
> >
> > Note the additional "EMERG: " in front of each continuation, which is
> > inserted by pr_cont(buf) being expanded to pr_printk(0, buf). These
> > additional strings show up in deep red on the console (which is not
> > supported in Git commit messages…). One might argue that this is the
> > same color as the "ERROR: " prefix, but when pr_cont() is used with
> > pr_notice() and pr_warning(), which are printed in blue and yellow
> > respectively, at least then the change in color would lead to additional
> > confusion.
> >
> > The log level argument to pr_printk is defined as int, so we can solve
> > this by defining the level for pr_cont() to -1, which is not used for
> > any loglevel:
> >
> > ERROR: HABv4: -------- HAB warning Event 0 --------
> > ERROR: HABv4: event data:
> > ERROR: HABv4: db 00 24 42 69 30 e1 1d
> > ERROR: HABv4: 00 04 00 02 40 00 36 06
> > ERROR: HABv4: 55 55 00 03 00 00 00 00
> > ERROR: HABv4: 00 00 00 00 00 00 00 00
> > ERROR: HABv4: 00 00 00 01
> > ERROR: HABv4: Status: Operation completed with warning (0x69)
> >
> > Fixes: 0fcefdd9369050f35a88b41dcd42cc5a3c6c6b33 ("printk: Add pr_cont")
> > Fixes: ea0e077ed65a003e4d7a1e023aee38cbe2d14898 ("printk: Fix pr_cont")
> > Signed-off-by: Roland Hieber <r.hieber@xxxxxxxxxxxxxx>
> > ---
> > include/printk.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/printk.h b/include/printk.h
> > index 4384fb85ea..858e800543 100644
> > --- a/include/printk.h
> > +++ b/include/printk.h
> > @@ -84,21 +84,21 @@ static inline int pr_print(int level, const char *format, ...)
> > #define pr_emerg(fmt, arg...) __pr_printk(0, pr_fmt(fmt), ##arg)
> > #define pr_alert(fmt, arg...) __pr_printk(1, pr_fmt(fmt), ##arg)
> > #define pr_crit(fmt, arg...) __pr_printk(2, pr_fmt(fmt), ##arg)
> > #define pr_err(fmt, arg...) __pr_printk(3, pr_fmt(fmt), ##arg)
> > #define pr_warning(fmt, arg...) __pr_printk(4, pr_fmt(fmt), ##arg)
> > #define pr_notice(fmt, arg...) __pr_printk(5, pr_fmt(fmt), ##arg)
> > #define pr_info(fmt, arg...) __pr_printk(6, pr_fmt(fmt), ##arg)
> > #define pr_debug(fmt, arg...) __pr_printk(7, pr_fmt(fmt), ##arg)
> > #define debug(fmt, arg...) __pr_printk(7, pr_fmt(fmt), ##arg)
> > #define pr_vdebug(fmt, arg...) __pr_printk(8, pr_fmt(fmt), ##arg)
> > -#define pr_cont(fmt, arg...) __pr_printk(0, fmt, ##arg)
> > +#define pr_cont(fmt, arg...) __pr_printk(-1, fmt, ##arg)
>
> Hmmm. There is a different ugly detail here: pr_cont()s are always
> printed regardless of the current loglevel, also with the old
> implementation. I think we could remember the last used loglevel in
> pr_debug(), pr_err(), pr_info() etc. code paths and let pr_printk()
> decide on that basis if pr_cont() should be printed or not, i.e. from
> which loglevel the current pr_cont() is a continuation.
I just gave it a try and there's a problem with this. Right now with
default settings pr_debug is completely optimized out. If we have to
store the state in pr_debug in order to safe it for a pr_cont then
pr_debug is no longer fully optimized away and the binary gets
significantly bigger.
Sascha
--
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