Date: Sun, 31 Jul 2016 14:22:35 -0700 From: John Baldwin <jhb@freebsd.org> To: gljennjohn@gmail.com Cc: current@freebsd.org Subject: Re: EARLY_AP_STARTUP hangs during boot Message-ID: <1944919.bPt123bEA6@ralph.baldwin.cx> In-Reply-To: <20160731112914.58bd9765@ernst.home> References: <20160516122242.39249a54@ernst.home> <8097239.52FCHCROUA@ralph.baldwin.cx> <20160731112914.58bd9765@ernst.home>
next in thread | previous in thread | raw e-mail | index | archive | help
On Sunday, July 31, 2016 11:29:14 AM Gary Jennejohn wrote:
> On Sat, 30 Jul 2016 12:03:59 -0700
> John Baldwin <jhb@freebsd.org> wrote:
>
> > On Saturday, July 30, 2016 09:44:22 AM Gary Jennejohn wrote:
> > > On Fri, 29 Jul 2016 13:17:42 -0700
> > > John Baldwin <jhb@freebsd.org> wrote:
> > >
> > > > On Thursday, July 28, 2016 12:31:31 AM Gary Jennejohn wrote:
> > > > > Well, now I know that ULE is a prerequiste for EARLY_AP_STARTUP! I
> > > > > wasn't aware of that. I prefer BSD and that's the scheduler I did
> > > > > the first tests with.
> > > > >
> > > > > But with the ULE scheduler the system comes up all the way.
> > > > >
> > > > > It would be nice if the BSD scheduler could also be modified to
> > > > > work with EARLY_AP_STARTUP.
> > > >
> > > > I wasn't able to reproduce your hang with 4BSD, but I think I see a
> > > > possible problem. Try this:
> > > >
> > > > diff --git a/sys/kern/sched_4bsd.c b/sys/kern/sched_4bsd.c
> > > > index 7de56b6..d53331a 100644
> > > > --- a/sys/kern/sched_4bsd.c
> > > > +++ b/sys/kern/sched_4bsd.c
> > > > @@ -327,7 +327,6 @@ maybe_preempt(struct thread *td)
> > > > * - The current thread has a higher (numerically lower) or
> > > > * equivalent priority. Note that this prevents curthread from
> > > > * trying to preempt to itself.
> > > > - * - It is too early in the boot for context switches (cold is set).
> > > > * - The current thread has an inhibitor set or is in the process of
> > > > * exiting. In this case, the current thread is about to switch
> > > > * out anyways, so there's no point in preempting. If we did,
> > > > @@ -348,7 +347,7 @@ maybe_preempt(struct thread *td)
> > > > ("maybe_preempt: trying to run inhibited thread"));
> > > > pri = td->td_priority;
> > > > cpri = ctd->td_priority;
> > > > - if (panicstr != NULL || pri >= cpri || cold /* || dumping */ ||
> > > > + if (panicstr != NULL || pri >= cpri /* || dumping */ ||
> > > > TD_IS_INHIBITED(ctd))
> > > > return (0);
> > > > #ifndef FULL_PREEMPTION
> > > > @@ -1127,7 +1126,7 @@ forward_wakeup(int cpunum)
> > > > if ((!forward_wakeup_enabled) ||
> > > > (forward_wakeup_use_mask == 0 && forward_wakeup_use_loop == 0))
> > > > return (0);
> > > > - if (!smp_started || cold || panicstr)
> > > > + if (!smp_started || panicstr)
> > > > return (0);
> > > >
> > > > forward_wakeups_requested++;
> > > >
> > >
> > > Thanks, but with this patch the kernel hangs in exactly the same
> > > place as before - after the HPET output.
> > >
> > > Maybe I'm missing some kernel option which ULE works around, or
> > > something like that.
> >
> > Hmm, ok. Please add KTR_RUNQ and KTR_SMP to the KTR masks, that is
> > 'options KTR_COMPILE=(KTR_PROC|KTR_RUNQ|KTR_SMP)' and
> > 'options KTR_MASK=(KTR_PROC|KTR_RUNQ|KTR_SMP)'
> >
> > Please also add this patch (on top of the previous patch):
> >
> > diff --git a/sys/kern/sched_4bsd.c b/sys/kern/sched_4bsd.c
> > index 2973a23..bab2278 100644
> > --- a/sys/kern/sched_4bsd.c
> > +++ b/sys/kern/sched_4bsd.c
> > @@ -1278,6 +1278,8 @@ sched_add(struct thread *td, int flags)
> > KASSERT(td->td_flags & TDF_INMEM,
> > ("sched_add: thread swapped out"));
> >
> > + CTR2(KTR_PROC, "sched_add: thread %d (%s)", td->td_tid,
> > + sched_tdname(td));
> > KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
> > "prio:%d", td->td_priority, KTR_ATTR_LINKED,
> > sched_tdname(curthread));
> > diff --git a/sys/x86/x86/cpu_machdep.c b/sys/x86/x86/cpu_machdep.c
> > index f07b97e..1f418f1 100644
> > --- a/sys/x86/x86/cpu_machdep.c
> > +++ b/sys/x86/x86/cpu_machdep.c
> > @@ -440,6 +440,7 @@ cpu_idle_wakeup(int cpu)
> > return (0);
> > if (*state == STATE_MWAIT)
> > *state = STATE_RUNNING;
> > + CTR1(KTR_PROC, "cpu_idle_wakeup: wokeup CPU %d", cpu);
> > return (1);
> > }
> >
> > (I haven't tried compiling it, you might have to add the sys/ktr.h
> > header to cpu_machdep.c if it doesn't build.)
> >
> > Hopefully we will get some better trace messages before it hangs
> > with this added info. The root issue seems to be that 4BSD is
> > pinning thread0 to some other CPU (due to sched_bind that happens
> > inside of bus_bind_intr() when the HPET driver pins IRQs to CPUs)
> > and that other CPU isn't waking up to realize it needs to run thread0.
> >
>
> It compiled with no changes needed.
>
> Even though I set MAXCPU to a mere 2, the boot still hadn't
> completed after 90 minutes and I broke it off. I still have
> the kernel, so I can try it another time when I have less need
> for my FreeBSD box.
Did you have the KTR options enabled from before? I don't expect this
to fix the issue, this is more about getting better debug info when it
hangs.
--
John Baldwin
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?1944919.bPt123bEA6>