Date: Thu, 24 Mar 2016 16:01:51 +0100 From: Edward Tomasz =?utf-8?Q?Napiera=C5=82a?= <trasz@FreeBSD.org> To: Alexander Motin <mavbsd@gmail.com> Cc: =?iso-8859-1?Q?Jean-S=E9bastien_P=E9dron?= <jean-sebastien.pedron@dumbbell.fr>, Ian Lepore <ian@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r297190 - head/sys/kern Message-ID: <20160324150151.GA1277@brick.home> In-Reply-To: <56F3F52F.9040705@gmail.com> References: <201603221346.u2MDk1XH029623@repo.freebsd.org> <1458662141.1091.16.camel@freebsd.org> <56F29654.8030806@dumbbell.fr> <20160323174537.GA1826@brick.home> <56F3B441.6030602@dumbbell.fr> <20160324134222.GA1442@brick.home> <56F3F52F.9040705@gmail.com>
index | next in thread | previous in thread | raw e-mail
On 0324T1609, Alexander Motin wrote:
> On 24.03.16 15:42, Edward Tomasz Napierała wrote:
> > 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).
>
> Kernel threads run with absolute priorities, so if somehow this threads
> happen to have higher or equal priority then callout thread, or the
> kernel is built without PREEMPTION, then the last may never be executed
> until this thread get to sleep or at least call sched_yield().
The callout's td_priority seems to be 40; the thread running the prompt
is 84, so it's lower.
I've just noticed another curious thing, though: when you press ScrLk,
the screen gets immediately refreshed; also, pressing arrows works just
the way it should. In other words, the refresh is broken except for
the ScrlLk mode, where it works as it should.
home |
help
Want to link to this message? Use this
URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20160324150151.GA1277>