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Miller" , Andreas Larsson , Bradley Morgan , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org Subject: Re: [PATCH v3 2/3] s390: Implement arch_do_panic Message-ID: <20260730142344.70140A38-hca@linux.ibm.com> References: <20260730-arch_do_panic-v3-0-d5401e683cdb@linux.ibm.com> <20260730-arch_do_panic-v3-2-d5401e683cdb@linux.ibm.com> <20260730115445.18059Aac-hca@linux.ibm.com> Precedence: bulk X-Mailing-List: sparclinux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Info: AW1haW4tMjYwNzMwMDEwOSBTYWx0ZWRfXwlsoQpjNQPE+ +rnCfD7U0/L6da0T3ZjuajjHk5StLGZY+cFRy4cJmjeKdUYXKHnnjkLuZBHuYTLO9xZatg0kc8I V8BgB5/LrRjSIl/xnqSLw9t6zIkyXic= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzMwMDEwOSBTYWx0ZWRfX+vCh3kb6SHXC vLKwBs7FIX+srubg0wiR1Tk2MhwsmK6FfnIDx2zZv31VYUeMEgn/WEFC4pB9ibqnA6HRf5+nZx2 8DuXugy5PhSuNQ3idneHKs036/llZ5zJWkViih3UYdpPTuqFxM0xeO+//l8/niyo9QXRzu/NkFJ T/LKiia2uG4peSH9Q++JT8yR32E4P9DAzw+qgIGKnd9iaEzhyPL5qH9HX6SqWkx7X+WaPbtanir BjZG3f8P2/j9gsmvo5UjVPgB01GrvQX6Sq1cV76y24CVg7Qt/xdUJl781wYYiOrSKL9kfXBRfAo 6+10+yXvxUsFtrHpaQGntXLw17x87rmbp3/fK1ljFBBJDHzfLqal+9EevoNy4FfpZX1m38311oT SYkjIWZGqhZLNgai3CpN7uS3n0Ze2jUDa2KR8pMVXHY5baNMIALCC2TzWxeLihsqNWGfYW8lq8+ h8q2RNTeMeEPAYoWuFQ== X-Authority-Analysis: v=2.4 cv=b5WCJNGx c=1 sm=1 tr=0 ts=6a6b5e77 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=kj9zAlcOel0A:10 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=TTVcD_D_EiJ8kuCfl7wA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-GUID: hYdfYg4Xle9IZDIfqTL9zftjHnt4z1zu X-Proofpoint-ORIG-GUID: hYdfYg4Xle9IZDIfqTL9zftjHnt4z1zu 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=2026-07-30_04,2026-07-29_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 spamscore=0 adultscore=0 malwarescore=0 impostorscore=0 bulkscore=0 phishscore=0 suspectscore=0 clxscore=1015 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607300109 On Thu, Jul 30, 2026 at 03:15:31PM +0200, Mete Durlu wrote: > On 30/07/2026 13:54, Heiko Carstens wrote: > > Question: why is it desirable that panic_timeout takes precedence? The result > > of this change is quite surprising: if anybody (e.g. a distribution) sets > > CONFIG_PANIC_TIMEOUT to a non-zero value this completely breaks "on_panic" > > behaviour on s390. > > panic timeout can be set during boot or compile time as you said, so it > can be used to determine what will happen to a system if it panics > during boot along with after boot. Since panic timeout covers a larger > area I thought it should get precedence. > Being able to choose what will happen on panic before boot is a super > power IMO and would help immensely if one would like to boot an untested > kernel via kexec for example. Wouldn't it then not make more sense to add an s390 specific kernel command line parameter which _disables_ the notifier entirely, and then you get your panic_timeout working? Then you have to explicitely state what you want and don't get suprised by subtle semantic changes. > > I could understand if this change would result in a larger timeout and > > additional information being printed, but not that it breaks existing and > > actually designed and desired behaviour. > > For that to happen users have to "misconfigure" the system and try to > use both panic_timeout and a custom "on_panic" action. The same goes for > kdump, when kdump is configured "on_panic" actions are ignored silently > and system always dumps on panic. This is really not the same. If setting panic_timeout would disable something else that would be surprising at least, especially since it never did before.