linux-kernel - Re: [PATCH 0/2] net: mvpp2: Survive CPU hotplug events

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Message-ID: <CAPv3WKf4RFeTDCsW+cY-Rp=2rZt1HuZSVQcmcB3oKQKNbvBtDA@mail.gmail.com>
Date:   Wed, 16 Feb 2022 14:19:30 +0100
From:   Marcin Wojtas <mw@...ihalf.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        John Garry <john.garry@...wei.com>, kernel-team@...roid.com
Subject: Re: [PATCH 0/2] net: mvpp2: Survive CPU hotplug events

Hi Marc,

śr., 16 lut 2022 o 10:08 Marc Zyngier <maz@...nel.org> napisał(a):
>
> I recently realised that playing with CPU hotplug on a system equiped
> with a set of MVPP2 devices (Marvell 8040) was fraught with danger and
> would result in a rapid lockup or panic.
>
> As it turns out, the per-CPU nature of the MVPP2 interrupts are
> getting in the way. A good solution for this seems to rely on the
> kernel's managed interrupt approach, where the core kernel will not
> move interrupts around as the CPUs for down, but will simply disable
> the corresponding interrupt.
>
> Converting the driver to this requires a bit of refactoring in the IRQ
> subsystem to expose the required primitive, as well as a bit of
> surgery in the driver itself.
>
> Note that although the system now survives such event, the driver
> seems to assume that all queues are always active and doesn't inform
> the device that a CPU has gone away. Someout who actually understand
> this driver should have a look at it.
>
> Patches on top of 5.17-rc3, lightly tested on a McBin.
>

Thank you for the patches. Can you, please, share the commands you
used? I'd like to test it more.

Best regards,
Marcin

> Marc Zyngier (2):
>   genirq: Extract irq_set_affinity_masks() from
>     devm_platform_get_irqs_affinity()
>   net: mvpp2: Convert to managed interrupts to fix CPU HP issues
>
>  drivers/base/platform.c                       | 20 +-----
>  drivers/net/ethernet/marvell/mvpp2/mvpp2.h    |  1 -
>  .../net/ethernet/marvell/mvpp2/mvpp2_main.c   | 67 ++++++++++---------
>  include/linux/interrupt.h                     |  8 +++
>  kernel/irq/affinity.c                         | 27 ++++++++
>  5 files changed, 72 insertions(+), 51 deletions(-)
>
> --
> 2.30.2
>