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Tue, 28 Jul 2026 10:43:17 +0000 (GMT) Received: from [9.224.76.67] (unknown [9.224.76.67]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 28 Jul 2026 10:43:17 +0000 (GMT) Message-ID: <5b9f08f0-4412-4841-b7c1-21de21557fe4@linux.ibm.com> Date: Tue, 28 Jul 2026 12:43:17 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/3] s390: Implement arch_do_panic To: Bradley Morgan Cc: 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, svens@linux.ibm.com References: <8E5EEFE6-C655-4319-B659-E3817DD24954@grrlz.net> Content-Language: en-US From: Mete Durlu In-Reply-To: <8E5EEFE6-C655-4319-B659-E3817DD24954@grrlz.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: AzCsHLvmTIx-IUhh874i6A8fYheMLl_C X-Proofpoint-ORIG-GUID: AzCsHLvmTIx-IUhh874i6A8fYheMLl_C X-Proofpoint-Spam-Info: AW1haW4tMjYwNzI4MDA5MCBTYWx0ZWRfX4IgzPpFcKjBL iHCFUDQog44ErDqewXETDhx9zwX9zeNLq8EK30UU2foMGZx7Nd/VG2B0n2ZSHDQjXiFlRtzLf9I Vi9h86zC2uN+4u6t59nKJTQNcoUyOng= X-Authority-Analysis: v=2.4 cv=dYuwG3Xe c=1 sm=1 tr=0 ts=6a6887ca cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=pu_0fIP_DWjBY3u_oFMA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzI4MDA5MCBTYWx0ZWRfX1Fs/pHPx/tke Y32k7uvFFE5jDM7LEQ3xYxtnjOj0Ry4iB+o3hIFPkT049iakRyfCHCZRGmkcenB3g64vAoaQ1Gm 6Bg3Qxn9/Xy6r685HrQ1WNCU6vGOX5b4RuT4e4YUn4+olOuWW7bsyn8dRUhDW0YfV1bY64wLitx 6tlGze3VWkmfnMbVx7F+ptXmI3avTcMwb5hAXXoTS7n3EhUQUCYR8raL6esE+9JBlb8PgOlnJzb ehEnRAq+3Gzhy7/oYgcjgvznTvGhPPMCE6bKMSkdypdYJXZnzKlLNBCm/pkAlmHdHEPEe3AIops g4ZpPUBx6A0pCxsEvW8IWdQTCD73hpiJW/z6a9rIY1txqvwNSR1L2Sih88UAD2BnRMfe6iM01w+ HSYeGa22w0LCTKDelR/XnJhupvdOS2YMwCSZSdWaTGknV8ABiB9RIQgzJyQIzJaJAiQM9Gx2ZFB V6eIWWZ0G0u79mk4Q7w== 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_02,2026-07-27_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 clxscore=1015 phishscore=0 malwarescore=0 spamscore=0 lowpriorityscore=0 bulkscore=0 suspectscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607280090 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. 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