svn commit: r297190 - head/sys/kern

[Edward Tomasz Napierała]

On 0324T1032, Jean-Sébastien Pédron wrote:
> On 23/03/2016 18:45, Edward Tomasz Napierala wrote:
> >> So maybe callouts are disabled in this situation. If there is a way to
> >> detect that, then vt(4) can go back to a "synchronous mode" where it
> >> refreshes the screen after each typed character, like it does when ddb
> >> is active.
> > 
> > Looks like that's the case: for some reason the callouts don't work.
> > This trivial hack is a (mostly) working workaround:
> > 
> > Index: svn/head/sys/kern/kern_cons.c
> > ===================================================================
> > --- svn/head/sys/kern/kern_cons.c	(revision 297210)
> > +++ svn/head/sys/kern/kern_cons.c	(working copy)
> > @@ -430,6 +430,7 @@ cngets(char *cp, size_t size, int visible)
> >  	lp = cp;
> >  	end = cp + size - 1;
> >  	for (;;) {
> > +		pause("meh", 1);
> 
> Could you please explain how this works to me? Does calling pause() here
> give a chance to interrupt handlers or other threads of running?

It looks like it allows the callout to run.  I've did an experiment
and added a simple callout that printed something each second; during
the root mount prompt it doesn't get run unless you type '.', which
calls pause(9).

And, for the record, https://reviews.freebsd.org/D5724 doesn't fix
the problem.