Re: reboot hesitation on Pi3 running -current

On Nov 28, 2023, at 12:27, Steve Rikli <sr@genyosha.net> wrote:

> On Tue, Nov 28, 2023 at 12:00:08PM -0800, bob prohaska wrote:
>> On Tue, Nov 28, 2023 at 09:05:59AM -0800, Steve Rikli wrote:
>>> On Tue, Nov 28, 2023 at 08:15:30AM -0800, bob prohaska wrote:
>>>> On Tue, Nov 28, 2023 at 07:20:03AM -0800, Mark Millard wrote:
>>>>> On Nov 28, 2023, at 07:10, bob prohaska <fbsd@www.zefox.net> wrote:
>>>>> 
>>>>>> A Pi3 running -current has taken to pausing during a shutdown
>>>>>> -r in a strange way: It gets to: 
>>>>>> 
>>>>>> Hit [Enter] to boot immediately, or any other key for command
>>>>>> prompt.  Booting [/boot/kernel/kernel] in 5 second more
>>>>>> detailed help.
>>>>>> 
>>>>>> It then stops at the OK prompt:
>>>>>> 
>>>>>> OK boot <---typing boot fails:
>>>>>> 
>>>>>> unknown command <---this looks strange, the kernel should
>>>>>> already be loaded
>>>>> 
>>>>> A possibility here is garbage control characters, say before
>>>>> the "boot". YOu might want to type just <return> to the first OK
>>>>> prompt and see if you ever still get "unknown command" once you
>>>>> do type just "boot" (and <return>).
>>>> 
>>>> IIRC I've done that in the past with the same result, but memory
>>>> is hazy and an attempt at a second shutdown -r came back up
>>>> without hesitation.
>>>> 
>>>> Another build/install cycle is running now, I'll be more careful
>>>> next time.
>>>> 
>>>>> The fact that the countdown stopped at 5 (or other early value)
>>>>> suggests such extra text at that point.
>>>> 
>>>> Rubbish on the serial console is a common occurence, but it usually
>>>> shows up when the USB end is taken down and brought back up. In this
>>>> case the USB end remained up throughout the reboot cycle, no stray 
>>>> characters were visible.
>>> 
>>> This topic has come up before here, I believe.
>>> 
>>> I can confirm the same or very similar behavior on rpi4, and there's no
>>> USB-serial to disconnect on the remote end, rather an actual serial
>>> console server which is always-on.
>> 
>> That's a significant (I think) observation. I couldn't tell where the
>> stray characters were originating and suspected the USB-serial
>> adapter. Your experience suggests very strongly the trouble is local
>> to the serial UART on the Pi or maybe wiring problems. 
> 
> I tend to agree. No USB-serial adapters involved in my setup. Wrt
> "wiring problem", fwiw I've tried multiple cables and db9 hoods, with
> both full-pins and 3-wire, no difference. All work as expected on other
> systems (NUC, various x86 PC, the occasional network gear etc.).
> 
>> Is it possible that the serial port of the monitoring devices occasionally
>> echos output from the Pi's console back to the Pi? Seems to me it shouldn't,
>> but sometimes I see fragments of a login prompt among the rubbish. 
> 
> I imagine it's possible but I doubt it's happening. I've swapped ports on
> the serial console server as well JIC, again no change, and no other systems
> or devices exhibit behavior like this.
> 
>>> Unfortunately it's not consistent behavior, i.e. sometimes the reboot
>>> proceeds uninterrupted. Sometimes typing 'boot' proceeds normally,
>>> sometimes typing 'boot' errors and then typing it again proceeds as
>>> normal.
>> 
>> Does it sometimes reboot hands-off? Mine does, at least occasionally.
> 
> Yes, sorry, that's what I meant by "sometimes reboot proceeds uninterrupted".
> 
>>> I too have been thinking it's spurious chars on the serial console at
>>> various points, but I've yet to find a common behavior or consistent
>>> method to reproduce. This doesn't happen on my other serial consoles,
>>> FreeBSD or Linux. I also don't think it happened early on when this
>>> rpi4 was running raspbian for a brief time, but I didn't play with
>>> that setup very long.
>>> 
>>> So far I believe it's avoidable by not watching the serial console
>>> during reboot, not necessary (I think) to disconnect the cable. But
>>> obviously that defeats the purpose of the serial console vs. a blind
>>> reboot.
>> 
>> Hopefully "not watching" means disconnecting Rx and Tx from the GPIO
>> pins. If it means not looking at the display it's a whole 'nother story!
>> 
>> 8-)
> 
> Nothing is ever physically disconnected from the rpi4, if that's what you
> mean. Fyi my rpi4 serial console is via a "Serial Hat" which ultimately
> connects the appropriate GPIO pins to a db9 connector accessible outside
> the case, which is in-turn connected to my serial console server.
> 
> "Not watching" in this context means I do not have an active connection
> to the serial console server port which communicates with the rpi4 db9
> serial port.
> 
> Somewhat analagous to not running tip/cu/minicom from your laptop or
> whatever system you use to connect to the rpi4 GPIO pins.
> 
> Another note JIC: there are no keyboard, mouse, HDMI, or USB devices
> connected to any of the rpi4 ports. Only power, the serial console and
> a network cable. In that regard it is a neat little headless server,
> but unfortunately I don't really want to use it in production due to
> this issue.

I'm going to remind of the known issue with U-Boot on the RPi*'s
sometimes leading to odd serial connection behavior for the
transition from U-Boot based UEFI handling the serial connection
to the FreeBSD UEFI loader handling it.

===
Mark Millard
marklmi at yahoo.com