Re: [PATCH v2 2/3] s390: Implement arch_do_panic

On 28 July 2026 11:43:17 BST, Mete Durlu <[email protected]> wrote:
>On 27/07/2026 15:01, Bradley Morgan wrote:
>
>Hi Bradley,
>
>>> This now means that the panic_timeout value takes precedence over user
>>> defined on_panic behavior.
>> 
>> this is the part i want to poke at. distros routinely ship panic=N on
>> the cmdline. with this change, anyone who configured on_panic=dump on
>> such a system silently stops getting dumps, because
>> emergency_restart() runs first and never returns. a reboot instead of
>> the dump you explicitly asked for is strictly worse. if you and Sven
>> want that semantic, fine, but spell it out properly and give the s390
>> docs for on_panic a line about the new precedence.
>
>FWICT, there is no mention of shutdown actions in kernel documentation.
>s390's user documentation is a different story. I agree it should be
>documented on Linux on IBM systems documentation.
>
>I'd argue that specifying both on_panic=dump and panic=N (N>0) is
>a configuration error, but maybe a pr_warn() could be added to the
>when on_panic=dump is configured with panic=N is set. That could
>hint what is wrong if anyone investigating dmesg and trying to
>figure out why system didn't dump.
>


hey, sorry I'm out, so I can't do the most massive think ever, and I may
embarrass myself, heh.

I think a BUG would be sufficient, we would want to shut down the system
with said bug, I know about panic on warn, but sometimes that's not always
enabled, something like a BUG would be good, what do you think?

>On another note, dumping via shutdown actions serves as a backup
>and kdump is the main dump mechanism nowadays. Kdump always takes
>precedence over panic=N.
>
>> also worth saying in the changelog what this actually wins: today the
>> INT_MIN notifier never returns, so sys_info, kmsg_dump, the post
>> notifier crash_kexec path, the console flushes and the end banner
>> never execute on s390 once on_panic fires. after this patch they all
>> do. thats the headline and the changelog undersells it.
>> 
>
>Right, I will add that part to the commit message too.
>
>>> Fixes: ff6b8ea68f4b ("[S390] ipl/dump on panic.")
>> 
>> What's broken? What's buggy? 
>
>I can put a couple of sentences on how and why panic=
>kernel command line argument was broken for s390.
>> s/now allow/now allows/ in the changelog..
>
>Will fix in next version!
>
>Thank you
>
>

Thanks!