linux-kernel - Re: pciehp 0000:00:1c.0:pcie004: Timeout on hotplug command 0x1038 (issued 65284 msec ago)

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Message-ID: <b62c2a8e-fe14-6d7d-147c-0ce3b0c0ab2f@codeaurora.org>
Date:   Fri, 27 Apr 2018 15:34:30 -0400
From:   Sinan Kaya <okaya@...eaurora.org>
To:     Bjorn Helgaas <helgaas@...nel.org>,
        Paul Menzel <pmenzel+linux-pci@...gen.mpg.de>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, Lukas Wunner <lukas@...ner.de>
Subject: Re: pciehp 0000:00:1c.0:pcie004: Timeout on hotplug command 0x1038
 (issued 65284 msec ago)

Hi Bjorn,

Thanks for adding me.

On 4/27/2018 3:22 PM, Bjorn Helgaas wrote:
> Sinan mooted the idea of using a "no-wait" path of sending the "don't
> generate hotplug interrupts" command.  I think we should work on this
> idea a little more.  If we're shutting down the whole system, I can't
> believe there's much value in *anything* we do in the pciehp_remove()
> path.
> 
> Maybe we should just get rid of pciehp_remove() (and probably
> pcie_port_remove_service() and the other service driver remove methods)
> completely.  That dates from when the service drivers could be modules that
> could be potentially unloaded, but unloading them hasn't been possible for
> years.

Shutdown path is also used for kexec. Leaving hotplug interrupts pending is
dangerous for the newly loaded kernel as it leaves spurious interrupts
during the new kernel boot.

I think we should always disable the hotplug interrupt on shutdown. We might
think of not waiting for command-completion as a middle-ground or go to polling
path instead of interrupts all the time.

Sinan

-- 
Sinan Kaya
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.