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McKenney" Subject: Re: [linux-next][s390] Boot hang after merge c50f05bd3c4e (sched/hrtick) Message-ID: <20260305194821.8663A9e-hca@linux.ibm.com> References: <28add480-4841-4e6a-a8a9-1211280ecc51@linux.ibm.com> <20260305074922.7170Ad3-hca@linux.ibm.com> <20260305121201.GB596554@noisy.programming.kicks-ass.net> <20260305123505.GA1395416@noisy.programming.kicks-ass.net> <20260305124501.GB1395416@noisy.programming.kicks-ass.net> <20260305130725.GB652779@noisy.programming.kicks-ass.net> <20260305150210.7170D10-hca@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-next@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-ORIG-GUID: aoE729KLzwmwOg3HuJ85cp9VEJ0pVU_Z X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzA1MDE2NCBTYWx0ZWRfX5iLlZn5O/PEq 87GYPRFUbgVhVEXOHgHarct+0F0R/X43avO3wPH1nhqBjOGC01iajblI/OrtgO7ZK4yi8VbFl2S YUS2Yib4qUegF3Lh709C3WlBwPcH5/UgZUvCu9dHR2VdQII+oiOsT2q+OGe1fi8y0C8gJh0YHZM cKYBjn/IsEuwB1Bl3KQ6HM5kwpaVPRzPS3ksdnjpbMoPuHiWCD3ZpWq22JXkxwQltK2qFT/DmLi EMJ6pGyANgqITKgTCABs0sxho8DUmsiUV10Sxz+j13CqZ7yX1X5iWpltcpB1mnuTuXMIT7EnXt+ iPPywAkIFdx4cb9BD43xEGnVRDnWYt21/96HSxy8VMiY88i+0LztBsVANhrxMfn8+Nv9amoro1V DVjaoH4HCCLoxe+o6teddMfPWsfxkeQyMGiynDTeRtLfQ8SEA8JgjOWpac2qATEN4aXwSu2wa6Q DDnJ/bauKZkaCgI2h6A== X-Authority-Analysis: v=2.4 cv=csCWUl4i c=1 sm=1 tr=0 ts=69a9de0c cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=kj9zAlcOel0A:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=HJzEO1QZ-oQFQT59-5gA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-GUID: aoE729KLzwmwOg3HuJ85cp9VEJ0pVU_Z X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-05_05,2026-03-04_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 priorityscore=1501 suspectscore=0 malwarescore=0 adultscore=0 clxscore=1015 bulkscore=0 phishscore=0 spamscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2602130000 definitions=main-2603050164 On Thu, Mar 05, 2026 at 06:24:48PM +0100, Mikhail Zaslonko wrote: > >> Another change is that you clear I and E in the PSW bit before > >> irq_enter_rcu(), which, per: > >> > >> 7e641e52cf5f ("softirq: Prepare for deferred hrtimer rearming") > >> > >> can re-arm the timer. > >> > >> So where previously it would re-arm and still have the I/E bits set, so > >> the timer could fire, they are now disabled. > >> > >> I really don't know if this is a problem; I'm clutching at s390 straws > >> here that I really don't know much about. > > > > That's the old PSW where the interrupt happened, not the one with which the > > CPU is running with, and shouldn't have any effect. > > > > ...but reverting that commit actually does fix it for me. > > For me it doesn't. But reverting this one helps: > 15dd3a948855 ("hrtimer: Push reprogramming timers into the interrupt return path") Mikhail, which commit did you revert? The above discussion is about commit d8b5cf9c6314 ("s390/irq/idle: Remove psw bits early"), which is not explicitly mentioned. But it is indeed broken: irqentry_exit() has a regs_irqs_disabled() check, which I broke with this commit - but "only" for idle exit. Result: no hrtimer_rearm_deferred() being called on idle exit. Oh well. Peter, thanks for pointing to this broken commit. Will be reverted.