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Sun, 19 Oct 2025 23:08:26 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHCfcVkBiu61OspSB+hr3+Eu+dpCS0oJKyzY5B2GW/2d+oKy9v8Txx/pdsyxDdViW8IOdN+1A== X-Received: by 2002:a05:600c:1e1f:b0:46f:b42e:e38d with SMTP id 5b1f17b1804b1-4711792a2admr85862135e9.40.1760940506470; Sun, 19 Oct 2025 23:08:26 -0700 (PDT) Received: from jlelli-thinkpadt14gen4.remote.csb ([176.206.13.103]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-427f00b9fdfsm13385253f8f.40.2025.10.19.23.08.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 19 Oct 2025 23:08:25 -0700 (PDT) Date: Mon, 20 Oct 2025 08:08:23 +0200 From: Juri Lelli To: Youngmin Nam Cc: Shrikanth Hegde , peterz@infradead.org, mingo@redhat.com, vincent.guittot@linaro.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, m.szyprowski@samsung.com, venkat88@linux.ibm.com, jstultz@google.com, d7271.choe@samsung.com, soohyuni.kim@samsung.com, bongkyu7.kim@samsung.com, jkkkkk.choi@samsung.com Subject: Re: [PATCH] sched/deadline: stop dl_server before CPU goes offline Message-ID: References: <20251009184727.673081-1-sshegde@linux.ibm.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: vW9s8z1PtiHPdNUhR_c4ZlKwesaWFuqEU-p6sLeMess_1760940507 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On 17/10/25 15:01, Youngmin Nam wrote: > On Tue, Oct 14, 2025 at 11:11:31AM +0200, Juri Lelli wrote: > > Hello, > > > > On 10/10/25 00:17, Shrikanth Hegde wrote: > > > From: Peter Zijlstra (Intel) > > > > > > IBM CI tool reported kernel warning[1] when running a CPU removal > > > operation through drmgr[2]. i.e "drmgr -c cpu -r -q 1" > > > > > > WARNING: CPU: 0 PID: 0 at kernel/sched/cpudeadline.c:219 cpudl_set+0x58/0x170 > > > NIP [c0000000002b6ed8] cpudl_set+0x58/0x170 > > > LR [c0000000002b7cb8] dl_server_timer+0x168/0x2a0 > > > Call Trace: > > > [c000000002c2f8c0] init_stack+0x78c0/0x8000 (unreliable) > > > [c0000000002b7cb8] dl_server_timer+0x168/0x2a0 > > > [c00000000034df84] __hrtimer_run_queues+0x1a4/0x390 > > > [c00000000034f624] hrtimer_interrupt+0x124/0x300 > > > [c00000000002a230] timer_interrupt+0x140/0x320 > > > > > > Git bisects to: commit 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck") > > > > > > This happens since: > > > - dl_server hrtimer gets enqueued close to cpu offline, when > > > kthread_park enqueues a fair task. > > > - CPU goes offline and drmgr removes it from cpu_present_mask. > > > - hrtimer fires and warning is hit. > > > > > > Fix it by stopping the dl_server before CPU is marked dead. > > > > > > [1]: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.com/ > > > [2]: https://github.com/ibm-power-utilities/powerpc-utils/tree/next/src/drmgr > > > > > > [sshegde: wrote the changelog and tested it] > > > Fixes: 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck") > > > Reported-by: Venkat Rao Bagalkote > > > Closes: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.com > > > Signed-off-by: Peter Zijlstra (Intel) > > > Signed-off-by: Shrikanth Hegde > > > Tested-by: Marek Szyprowski > > > Tested-by: Shrikanth Hegde > > > > Looks good to me. > > > > Acked-by: Juri Lelli > > > > Thanks! > > Juri > > > > Hi All, > > Could we expect this patch to address the following issue as well? > > https://lore.kernel.org/all/aMKTHKfegBk4DgjA@jlelli-thinkpadt14gen4.remote.csb/ I don't think I see a direct connection with it. Thanks, Juri