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Tue, 28 Jul 2026 11:40:19 +0000 (GMT) Received: from tuxmaker.linux.ibm.com (unknown [9.87.85.9]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTPS; Tue, 28 Jul 2026 11:40:18 +0000 (GMT) From: Sven Schnelle To: Bradley Morgan Cc: Mete Durlu , agordeev@linux.ibm.com, akpm@linux-foundation.org, andreas@gaisler.com, borntraeger@linux.ibm.com, davem@davemloft.net, gor@linux.ibm.com, hca@linux.ibm.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, pmladek@suse.com, sparclinux@vger.kernel.org Subject: Re: [PATCH v2 2/3] s390: Implement arch_do_panic In-Reply-To: References: <8E5EEFE6-C655-4319-B659-E3817DD24954@grrlz.net> <5b9f08f0-4412-4841-b7c1-21de21557fe4@linux.ibm.com> Date: Tue, 28 Jul 2026 13:40:18 +0200 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 X-Proofpoint-GUID: rd54aFSeey66jGI3caMB-sYY-VOJ9oJL X-Proofpoint-ORIG-GUID: rd54aFSeey66jGI3caMB-sYY-VOJ9oJL X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzI4MDA5OSBTYWx0ZWRfX8WyXWd2N5Z4B Osuf6LEGPlJvWG4THo6RZ7yvGnaZSey/wDybI5zz93kpTLSX2Sw8GTUJu35BahfjSfNBjAdIVt9 D6wbGJrPSJXUE9D6WesVO4X+NNBo4LtCQNoBTW7ouWAzsybTLsjoMxNir+en8jf7eyFoQQcB4NK YSfCL1EDzx2wrEukUEN0XL/EyV6TxmaVoK1l9FNPyBZe6oXXLnovN+RG8KPqKZ9OSjJgtihn3ee laJiBCr67iWIjO6V8hCCgP4uxTAwf4VttBhn54xEI/JrimVbuhzq0zAXpjkwHC6elcLgEAjK5yV AY5CPKYQJ6fk1VWStTAMCKyNaOTI5dVEbwGDMLwccuMogaBghM4eVuTt1ELg9oMi2jgMDAaJxdz mnobATwMupQ63/xHCrp0JlgrElbk1EJJZe5sXzqoOGKvx7xrJEWBl3hqRNJBBJP0QzgD++vmKfx BqSS5Lgot4FyrYxK0/g== X-Authority-Analysis: v=2.4 cv=SKFykuvH c=1 sm=1 tr=0 ts=6a689528 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=jcFIXsoQAAAA:8 a=VnNF1IyMAAAA:8 a=85Yt1j-L8YSk_LuRtnkA:9 a=M1-Q_cRM6PFdmZSamPpU:22 X-Proofpoint-Spam-Info: AW1haW4tMjYwNzI4MDA5OSBTYWx0ZWRfX/M/iNUSccYQU FVIA308JnWOwaE83QhjFlpyh+ePEfKX3EYK4RKxkefVxnSVYaqXY0dqABOjMx0fo1aZKdqBh6nX KyJkRXnCvw0XOOVrO9H/21K2CdhF5Ik= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-28_03,2026-07-28_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 clxscore=1011 adultscore=0 lowpriorityscore=0 bulkscore=0 impostorscore=0 phishscore=0 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607280099 Bradley Morgan writes: > On 28 July 2026 11:43:17 BST, Mete Durlu 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? Err... No. You don't want to make a mistake while updating the kernel panic parameters just to figure out that on the next boot the kernel just BUGs() because of that. There are of course lots of reasons why changing the kernel command line could end up in a non-bootable system but this one would be ridiculous.