linux-kernel - Re: MSI interrupt for xhci still lost on 5.6-rc6 after cpu hotplug

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Date:   Thu, 19 Mar 2020 13:24:12 -0700
From:   Evan Green <evgreen@...omium.org>
To:     Mathias Nyman <mathias.nyman@...ux.intel.com>
Cc:     x86@...nel.org, linux-pci <linux-pci@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Ghorai, Sukumar" <sukumar.ghorai@...el.com>,
        "Amara, Madhusudanarao" <madhusudanarao.amara@...el.com>,
        "Nandamuri, Srikanth" <srikanth.nandamuri@...el.com>
Subject: Re: MSI interrupt for xhci still lost on 5.6-rc6 after cpu hotplug

On Wed, Mar 18, 2020 at 12:23 PM Mathias Nyman
<mathias.nyman@...ux.intel.com> wrote:
>
> Hi
>
> I can reproduce the lost MSI interrupt issue on 5.6-rc6 which includes
> the "Plug non-maskable MSI affinity race" patch.
>
> I can see this on a couple platforms, I'm running a script that first generates
> a lot of usb traffic, and then in a busyloop sets irq affinity and turns off
> and on cpus:
>
> for i in 1 3 5 7; do
>         echo "1" > /sys/devices/system/cpu/cpu$i/online
> done
> echo "A" > "/proc/irq/*/smp_affinity"
> echo "A" > "/proc/irq/*/smp_affinity"
> echo "F" > "/proc/irq/*/smp_affinity"
> for i in 1 3 5 7; do
>         echo "0" > /sys/devices/system/cpu/cpu$i/online
> done
>
> I added some very simple debugging but I don't really know what to look for.
> xhci interrupts (122) just stop after a setting msi affinity, it survived many
> similar msi_set_affinity() calls before this.
>
> I'm not that familiar with the inner workings of this, but I'll be happy to
> help out with adding debugging and testing patches.

How quickly are you able to reproduce this when you run your script?
Does reverting Thomas' patch make it repro faster? Can you send the
output of lspci -vvv for the xhci device?

-Evan