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[87.142.58.163]) by smtp.gmail.com with ESMTPSA id q137sm20472339wmd.19.2016.08.02.00.03.11 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 02 Aug 2016 00:03:12 -0700 (PDT) Date: Tue, 2 Aug 2016 09:03:10 +0200 From: Gary Jennejohn To: John Baldwin Cc: current@freebsd.org Subject: Re: EARLY_AP_STARTUP hangs during boot Message-ID: <20160802090310.7a03d6d0@ernst.home> In-Reply-To: <9937686.eTkQvkYRyu@ralph.baldwin.cx> References: <20160516122242.39249a54@ernst.home> <20160801093434.410032f4@ernst.home> <20160801153111.5e59d3ce@ernst.home> <9937686.eTkQvkYRyu@ralph.baldwin.cx> Reply-To: gljennjohn@gmail.com X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.29; amd64-portbld-freebsd11.0) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 02 Aug 2016 07:03:15 -0000 On Mon, 01 Aug 2016 13:19:16 -0700 John Baldwin wrote: > On Monday, August 01, 2016 03:31:11 PM Gary Jennejohn wrote: > > On Mon, 1 Aug 2016 09:34:34 +0200 > > Gary Jennejohn wrote: > > > > > On Sun, 31 Jul 2016 14:22:35 -0700 > > > John Baldwin wrote: > > > > > > > On Sunday, July 31, 2016 11:29:14 AM Gary Jennejohn wrote: > > > > > On Sat, 30 Jul 2016 12:03:59 -0700 > > > > > John Baldwin wrote: > > > > > > > > > > > On Saturday, July 30, 2016 09:44:22 AM Gary Jennejohn wrote: > > > > > > > On Fri, 29 Jul 2016 13:17:42 -0700 > > > > > > > John Baldwin 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. > > > > > > > > > > Yes, all the options from before were enabled. Maybe I should have > > > disabled KTR_VERBOSE=1? I'll try it without that. > > > > > > > KTR_VERBOSE=1 is necessary. > > Yes. > > > OK, after about 5 hours it landed in an infinite loop emitting: > > > > cpu_0 ipi_cpu: cpu: 1 to 5 ipi: 2 (my CPU has 6 cores) > > Humm, can you capture a picture right when it hangs? Those interrupts > are due to clock interrupts (IPI_HARDCLOCK) and are noise. More what > I'm trying to see is if we send IPI_AST/IPI_PREEMPT to the CPU after > binding to it. > I can't tell when it hangs due to the amount of trace coming out. The hang is hidden in the noise and I have no way to suppress the trace that I'm aware of. The trace is coming so fast that even a photo of the screen looks smeared. Is there a way to limit the trace to IPI_AST/IPI_PREEMPT? I have, however, now switched to ULE and I'm running with EARLY_AP_STARTUP, but I'm willing run more tests with 4BSD. -- Gary Jennejohn