pciehp 0000:00:1c.0:pcie004: Timeout on hotplug command 0x1038 (issued 65284 msec ago)
okaya at codeaurora.org
okaya at codeaurora.org
Sat Apr 28 06:03:09 PDT 2018
On 2018-04-27 21:18, Dave Young wrote:
> On 04/28/18 at 08:56am, Dave Young wrote:
>> On 04/27/18 at 04:12pm, Bjorn Helgaas wrote:
>> > [+cc Eric, Vivek, kexec list]
>> > On Fri, Apr 27, 2018 at 03:34:30PM -0400, Sinan Kaya wrote:
>> > > 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
> Hmm, if it is the remove() method then kexec does not use it. kexec
> the shutdown() method instead. I missed this details when I replied.
Portdrv hooks up remove handler to shutdown. That's why remove is
>> > > > 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.
>> > Ah, I forgot about the kexec path. The kexec path is used for
>> > crashdump, too, so ideally the newly-loaded kernel would defend itself
>> > when possible so it doesn't depend on the original kernel doing things
>> > correctly.
>> It is true for kdump. But kexec needs device shutdown.
>> > Seems like this question of whether to do things in the original
>> > kernel or the kexec-ed kernel comes up periodically, but I can never
>> > remember a definitive answer. My initial reaction is that it'd be
>> > nice if we didn't have to do *any* shutdown in the original kernel,
>> > but I'm sure there are reasons that's not practical.
>> Devices sometimes assume it is in a good state initialized in firmware
>> phase, so we need a shutdown in 1st kernel so that kexec kernel can
>> correctly for those devices. For kdump since kernel already panicked
>> and it is not reliable so we do as less as we can in the 1st kernel
>> crash path, but there are some special handling for kdump in various
>> to reset the devices in 2nd kernel, eg. when it see "reset_devices"
>> kernel parameter.
>> > I copied Eric (kexec maintainer) and Vivek (contact listed in
>> > Documentation/kdump/kdump.txt) in case they have suggestions or would
>> > consider some sort of Documentation/ update.
>> > Bjorn
>> > _______________________________________________
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