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    SubjectRe: power-off delay/hang due to commit 6d25be57 (mainline)
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    On Thu, 14 May 2020 00:04:28 +0200 Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:

    > On 2020-05-08 23:30:45 [+0200], Stephen Berman wrote:
    >> > Can you log the output on the serial console?
    >>
    >> How do I do that?
    >
    > The spec for your mainboard says "serial port header". You would need to
    > connect a cable there to another computer and log its output.
    > The alternative would be to delay the output on the console and use a
    > camera.

    It's easiest for me to take a picture, since there isn't much output and
    in any case the delay happens on it's own ;-). I'm sending you the
    image (from kernel 5.6.4) off-list since even after reducing it it's 1.2
    MB large.

    >> > If the commit you cited is really the problem then it would mean that a
    >> > worker isn't scheduled for some reason. Could you please enable
    >> > CONFIG_WQ_WATCHDOG to see if workqueue core code notices that a worker
    >> > isn't making progress?

    I enabled that and also CONFIG_SOFTLOCKUP_DETECTOR,
    CONFIG_HARDLOCKUP_DETECTOR and CONFIG_DETECT_HUNG_TASK, which had all
    been unset previously.

    >> How will I know if that happens, is there a specific message in the tty?
    >
    > On the tty console where you see the "timing out command, waited"
    > message, there should be something starting with
    > |BUG: workqueue lockup - pool
    >
    > following with the pool information that got stuck. That code checks the
    > workqueues every 30secs by default. So if you waited >= 60secs then
    > system is not detecting a stall.

    As you can see in the photo, there was no message about a workqueue
    lockup, only "task halt:5320 blocked for more than <XXX> seconds" every
    two minutes. I suppose that comes from one of the other options I
    enabled. Does it reveal anything about the problem?

    > As far as I can tell, there is nothing special on your system. The CD
    > and disk drives are served by the AHCI controller. There is no special
    > SCSI/SATA/SAS controller.
    > Right now I have no idea how the workqueues fit in the picture. Could
    > you please check if the stall-dector says something?

    Is that the message I repeated above or do you mean the workqueue?

    > Is it possible to show me output when the timeout message comes? My
    > guess is that the system is going down and before unounting/remount RO
    > the filesystem it flushes its last data. But this is done before issuing
    > the "halt-syscall".

    The entire output from `shutdown -h now' is in the picture; after the
    fourth "timing out command" message, I pressed the reset button.

    Steve Berman

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