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SubjectRe: [PATCH v2] PCI/MSI: Avoid torn updates to MSI pairs
On Tue, Jan 28, 2020 at 2:48 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> Evan,
>
> Evan Green <evgreen@chromium.org> writes:
> > On Tue, Jan 28, 2020 at 6:38 AM Thomas Gleixner <tglx@linutronix.de> wrote:
> >> The patch is only lightly tested, but so far it survived.
> >>
> >
> > Hi Thomas,
> > Thanks for the patch, I gave it a try. I get the following splat, then a hang:
> >
> > [ 62.238406] CPU0
> > [ 62.241135] ----
> > [ 62.243863] lock(vector_lock);
> > [ 62.247467] lock(vector_lock);
> > [ 62.251071]
> > [ 62.251071] *** DEADLOCK ***
> > [ 62.251071]
> > [ 62.257687] May be due to missing lock nesting notation
> > [ 62.257687]
> > [ 62.265274] 2 locks held by migration/1/17:
> > [ 62.269946] #0: 00000000cfa9d8c3 (&irq_desc_lock_class){-.-.}, at:
> > irq_migrate_all_off_this_cpu+0x44/0x28f
> > [ 62.280846] #1: 000000006885da2d (vector_lock){-.-.}, at:
> > msi_set_affinity+0x13c/0x27b
> > [ 62.289801]
> > [ 62.289801] stack backtrace:
> > [ 62.294669] CPU: 1 PID: 17 Comm: migration/1 Not tainted 4.19.96 #2
> > [ 62.310713] Call Trace:
> > [ 62.313446] dump_stack+0xac/0x11e
> > [ 62.317255] __lock_acquire+0x64f/0x19bc
> > [ 62.321646] ? find_held_lock+0x3d/0xb8
> > [ 62.325936] ? pci_conf1_write+0x4f/0xdf
> > [ 62.330320] lock_acquire+0x1b2/0x1fa
> > [ 62.334413] ? apic_retrigger_irq+0x31/0x63
> > [ 62.339097] _raw_spin_lock_irqsave+0x51/0x7d
> > [ 62.343972] ? apic_retrigger_irq+0x31/0x63
> > [ 62.348646] apic_retrigger_irq+0x31/0x63
> > [ 62.353124] msi_set_affinity+0x25a/0x27b
>
> Bah. I'm sure I looked at that call chain, noticed the double vector
> lock and then forgot. Delta patch below.

It's working well with the delta patch, been running for about an hour
with no issues.
-Evan

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