linux-kernel - Re: [PATCH v2] PCI/MSI: Avoid torn updates to MSI pairs

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Date:   Thu, 30 Jan 2020 00:16:28 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Evan Green <evgreen@...omium.org>
Cc:     Rajat Jain <rajatja@...gle.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        linux-pci <linux-pci@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        x86@...nel.org, Marc Zyngier <maz@...nel.org>
Subject: Re: [PATCH v2] PCI/MSI: Avoid torn updates to MSI pairs

Evan,

Evan Green <evgreen@...omium.org> writes:
> On Wed, Jan 29, 2020 at 1:01 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>
>> Could you please add some instrumentation to see how often this stuff
>> actually triggers spurious interrupts?
>
> In about 10 minutes of this script running, I got 142 hits. My script
> can toggle the HT cpus on and off about twice per second.
> Here's my diff (sorry it's mangled by gmail). If you're looking for
> something else, let me know, or I can run a patch.
>
No, that's good data. Your testing is hiting the critical path and as
you did not complain about negative side effects it seems to hold up to
the expectations. I'm going to convert this to real patch with a
proper changelog tomorrow.

Thanks for your help!

       tglx