On Wed 2017-04-05 11:16:28, Sergey Senozhatsky wrote:
> On (04/05/17 11:08), Sergey Senozhatsky wrote:
> [..]
> > > stop_critical_timings(); /* don't trace print latency */
> > > - call_console_drivers(ext_text, ext_len, text, len);
> > > + call_console_drivers(ext_text, ext_len, text, len, msg->level);
> > > start_critical_timings();
> > > printk_safe_exit_irqrestore(flags);
> >
> > ok, so the idea is quite clear and reasonable.
> >
> >
> > some thoughts,
> > we have a system-wide suppress_message_printing() loglevel filtering
> > in console_unlock() loop, which sets a limit on loglevel for all of
> > the messages - we don't even msg_print_text() if the message has
> > suppressible loglevel. and this implicitly restricts per-console
> > maxlevels.
> >
> > console_unlock()
> > {
> > for (;;) {
> > ...
> > skip:
> >
> > if (suppress_message_printing(msg->level)) //
> > console_loglevel
> > goto skip;
> >
> > call_console_drivers(msg->level)
> > {
> > if (level > con->maxlevel) // con loglevel
> > continue;
> > ...
> > }
> > }
> > }
> >
> > this can be slightly confusing. what do you think?
>
> one more thing.
>
> this per-console filtering ignores... the "ignore_loglevel" param.
>
> early_param("ignore_loglevel", ignore_loglevel_setup);
> module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
> MODULE_PARM_DESC(ignore_loglevel,
> "ignore loglevel setting (prints all kernel messages to the
> console)");
>
>
> my preference would be preserve "ignore_loglevel" behaviour. if
> we are forced to 'ignore all loglevel filtering' then we should
> do so.
I think about a reasonable behavior. There seems to be three variables
that are related and are in use:
console_level
minimum_console_loglevel
ignore_loglevel
The functions seems to be the following:
+ console_level defines the current maximum level of
messages that appear on all enabled consoles; it
allows to filter out less important ones
+ minimum_console_loglevel defines the minimum
console_loglevel that might be set by userspace
via syslog interface; it prevents userspace from
hiding emergency messages
+ ignore_loglevel allows to see all messages
easily; it is used for debugging
IMPORTANT: console_level is increased in some special
situations to see everything, e.g. in panic(), oops_begin(),
__handle_sysrq().
I guess that people want to see all messages even on the slow
console during panic(), oops(), with ignore_loglevel. It means
that the new per-console setting must not limit it. Also
any console must not go below minimum_console_level.
What about doing it the other way and define min_loglevel
for each console. It might be used to make selected consoles
always more verbose (above current console_level) but it
will not limit the more verbose modes.
Best Regards,
Petr
