On Thu, Dec 28, 2017 at 10:48:35AM -0500, Alexandru Chirvasitu wrote:
> On Thu, Dec 28, 2017 at 03:48:15PM +0100, Thomas Gleixner wrote:
> > On Thu, 28 Dec 2017, Alexandru Chirvasitu wrote:
> > > On Thu, Dec 28, 2017 at 12:00:47PM +0100, Thomas Gleixner wrote:
> > > > Ok, lets take a step back. The bisect/kexec attempts led us away from the
> > > > initial problem which is the machine locking up after login, right?
> > > >
> > > 
> > > Yes; sorry about that..
> > 
> > Nothing to be sorry about.
> > 
> > >     x86/vector: Replace the raw_spin_lock() with
> > > 
> > > diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
> > > index 7504491..e5bab02 100644
> > > --- a/arch/x86/kernel/apic/vector.c
> > > +++ b/arch/x86/kernel/apic/vector.c
> > > @@ -726,6 +726,7 @@ static int apic_set_affinity(struct irq_data *irqd,
> > >                              const struct cpumask *dest, bool force)
> > >  {
> > >         struct apic_chip_data *apicd = apic_chip_data(irqd);
> > > +       unsigned long flags;
> > >         int err;
> > >  
> > >         /*
> > > @@ -740,13 +741,13 @@ static int apic_set_affinity(struct irq_data *irqd,
> > >             (apicd->is_managed || apicd->can_reserve))
> > >                 return IRQ_SET_MASK_OK;
> > >  
> > > -       raw_spin_lock(&vector_lock);
> > > +       raw_spin_lock_irqsave(&vector_lock, flags);
> > >         cpumask_and(vector_searchmask, dest, cpu_online_mask);
> > >         if (irqd_affinity_is_managed(irqd))
> > >                 err = assign_managed_vector(irqd, vector_searchmask);
> > >         else
> > >                 err = assign_vector_locked(irqd, vector_searchmask);
> > > -       raw_spin_unlock(&vector_lock);
> > > +       raw_spin_unlock_irqrestore(&vector_lock, flags);
> > >         return err ? err : IRQ_SET_MASK_OK;
> > >  }
> > > 
> > > With this, I still get the lockup messages after login, but not the
> > > freezes!
> > 
> > That's really interesting. There should be no code path which calls into
> > that with interrupts enabled. I assume you never ran that kernel with
> > CONFIG_PROVE_LOCKING=y.
> >
> 
> Correct. That option is not set in .config.
> 
> > Find below a debug patch which should show us the call chain for that
> > case. Please apply that on top of Dou's patch so the machine stays
> > accessible. Plain output from dmesg is sufficient.
> > 
> > > The lockups register in the log, which I am attaching (see below for
> > > attachment naming conventions).
> > 
> > Hmm. That's RCU lockups and that backtrace on the CPU which gets the stall
> > looks very familiar. I'd like to see the above result first and then I'll
> > send you another pile of patches which might cure that RCU issue.
> > 
> > Thanks,
> > 
> > 	tglx
> > 
> > 8<-------------------
> > --- a/arch/x86/kernel/apic/vector.c
> > +++ b/arch/x86/kernel/apic/vector.c
> > @@ -729,6 +729,8 @@ static int apic_set_affinity(struct irq_
> >  	unsigned long flags;
> >  	int err;
> >  
> > +	WARN_ON_ONCE(!irqs_disabled());
> > +
> >  	/*
> >  	 * Core code can call here for inactive interrupts. For inactive
> >  	 * interrupts which use managed or reservation mode there is no
> > 
> > 
> > 
> 
> Bit of a step back here: the kernel treated with Dou's patch no longer
> logs me in reliably as before, with or without this newest patch on
> top..
> 
> So now I sometimes get immediate lockups and freezes upon trying to
> log in, and other times I get logged in but get a freeze seconds
> later.
> 
> In no case can I roam around long nough to get a dmesg, and I no
> longer get the non-freezing lockups from before. I can't imagine what
> I could possibly have changed..
> 
> Here's the output of `git log --pretty=oneline -5` on the branch I'm
> working in.
> 
> --------------------
> 
> f2c02af5cc1d620c039b21fab0ca5948a06daf90 2nd tglx patch
> 7715575170bacf3566d400b9f2210a10ce152880 x86/vector: Replace the raw_spin_lock() with raw_spin_lock_irqsave()
> 8d9d56caf33d78bfe6b6087767b1b84acee58458 x86-32: fix kexec with stack canary (CONFIG_CC_STACKPROTECTOR)
> a197e9dea4ccb72e1a6457fac15329bd5319e719 irq/matrix: Remove the overused BUGON() in irq_matrix_assign_system()
> 464e1d5f23cca236b930ef068c328a64cab78fb1 Linux 4.15-rc5
> 
> --------------------
> 
> 7715575170bacf3566d400b9f2210a10ce152880, which is the kernel with
> Dou's patch, logged me in and allowed me to produce the dmesg from
> before. I did this a couple of times back then. I no longer can, for
> some reason, as it's reverted back to the no-go lockups from before.
> 
> And the next one, f2c02af5cc1d620c039b21fab0ca5948a06daf90, where I
> applied the patch you just sent, behaves identically.
> 
>

Actually, it decided to cooperate for just long enough for me to get
the dmesg out. Attached.

This is from the kernel you asked about: Dou's patch + yours, i.e. the
latest one in that git log I just sent, booted up with 'apic=debug'.