Messages in this thread | | | Date | Thu, 29 Sep 2022 10:29:05 +0100 | From | Conor Dooley <> | Subject | Re: [resend][bug] low-probability console lockups since 5.19 |
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On Thu, Sep 29, 2022 at 11:06:01AM +0200, Thorsten Leemhuis wrote: > Hi Conor > > On 28.09.22 18:55, Conor Dooley wrote: > > On Fri, Sep 23, 2022 at 05:24:17PM +0100, Conor Dooley wrote: > >> > >> Been bisecting a bug that is causing a boot failure in my CI & have > >> ended up here.. The bug in question is a low(ish) probability lock up > >> of the serial console, I would estimate about 1-in-5 chance on the > >> boards I could actually trigger it on which it has taken me so long > >> to realise that this was an actual problem. Thinking back on it, there > >> were other failures that I would retroactively attribute to this > >> problem too, but I had earlycon disabled > > [...] > > #regzbot introduced: 5831788afb17b89c5b531fb60cbd798613ccbb63 ^ > > Hopefully I did this correctly... > > Yes, you did, thx for this. I already had been watching this thread > manually and was a bit unsure what to do with it.
Great, thanks.
> > > I picked that commit as that's where things start going haywire. > > There is one thing I wonder when skimming this thread: was there maybe > some other change somewhere in the kernel between the introduction and > the revert of the printk console kthreads patches that is the real > culprit here that makes existing, older races easier to hit? But I guess > in the end that would be very hard to find and it's easier to fix the > problem in the console driver... :-/
Entirely possible that something arrived in the middle, yeah. I've done 100s of reboots on that interim section, albeit with the threaded printers enabled, as I restarted the bisection several times & never hit this failure then.
I don't know anything about console/printk/serial drivers unfortunately so I will almost certainly not be able to find the problem by inspection. I'd rather submit patches than send reports, but I really really need some help here. I looked at the two patterns Petr suggested, but the former I am not sure applies since the issue is present even when earlycon is disabled & the latter appears (to my untrained eye) to be accounted for in the 8250 driver.
Thanks, Conor.
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