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Wed, 02 Oct 2024 08:40:46 +0200 Message-ID: <12242825054bb861578de6405504875e4d1bb6c2.camel@gmx.de> Subject: Re: sched/fair: Kernel panics in pick_next_entity From: Mike Galbraith To: Vishal Chourasia Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, Ingo Molnar , Vincent Guittot , Juri Lelli , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , luis.machado@arm.com Date: Wed, 02 Oct 2024 08:40:44 +0200 In-Reply-To: <09e16088690e6577b60de489e6e52a3e5769f96f.camel@gmx.de> References: <20240930144157.GH5594@noisy.programming.kicks-ass.net> <55a2acefffb8c99e4234bd18656a75625447c2d0.camel@gmx.de> <09e16088690e6577b60de489e6e52a3e5769f96f.camel@gmx.de> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.42.4 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:jhj5PZvjMqouGBqy1K5kV5mmtIkrpkPAoj2lBKzJK9T71lnh686 SKB22Yi/xbOyKH9rA3kb/yYqQFr2EcuN3vpoZ4SjzXWULYgs0xy5NgRWfVk7yhQgjh9c3CA K8tfZ6zYvSTb6MjTysG1KxsbVpKJZw6iGZyAP0PHxP+C5PcEcIRmJ+wVxJ0yzLoj2xxz07h JJ/opoSF8TLRSph97M9rw== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:QpSexjVcPWk=;d+AXr70HESbkv013Y+eIbTfGt3c A2DZflCeZrp8c/5VwBRVE03pWkN/7PbOnVn1BUBwW0Wf1ly1KHD3OEtF5cKvE48OrbZh+Q65x imX2Ovls4jhLm3xglPSaMc+AWWlyPmKzF+FheFYdsNsGNGwU82p01vBoRfvQZ1JtIU819rIGe vmhe7CfC6FS7hEkS41riUFXq4R3WxbIpwSJ8TN1cW5SKsAo3KqhCk0eeseH6/qiJAgJfOWvIP niCAp/A/xuAvNy5PnZouOyhnBXE+jGle2+/tyPhUrUg9s1MubxtKhu45RtaCQrstXAXvcTeNB Co1Ir4QdeitzNGPofi745xvZqKiUoOeIAkJOfvzUmy0jXPEGD6Np4vl1B8pqmjHBLomKymYns QcruCjw9orhOjtXWYcjkYXGbFW/Vj5dpO6p5QeFw96+ORkXXLU8ZFfCKV5LEfQuMz2BI23mMS k2HygLRkFtiA7hOeIdcuBAUzCCXbZhUcNSyZSyT5fAe0k4qJ0uUG/ZkQENdKu9s8SaD09ifx3 hci8aTqPFlnVP13eYgngEuUI+VZ2KfKtxJ7iddZV/CApL+fLf6VjtAB2WOjQ29r1EUByLPj0S V9k9OR0lyRKG/wdF+2cwYbNy0UK807GL0afZk6VbNQuHY1aHvxD1qdR1iMhv4/7BudcuKznbZ RT4WMDXK0BrB0llWTO/Vt3lFOLfve6aC+O2EcE1I7IkZMa4oV9v02/tFKLI4WDtnrMyHv7T2Z 1bl4nv71YyNeRDRrKbBKl7ZVWfqNWmZLG6KhXPQbMyJzVacDWbPBW44EIX9fbplk24dIJ5qo/ +Lp9tKBwJG3xr0lS77X/nN9A== On Tue, 2024-10-01 at 18:41 +0200, Mike Galbraith wrote: > > When I hit $subject, LTPs cfs_bandwidth01 was running, but there was no > warning prelude, box went straight to panic.=C2=A0 Trying to reproduce u= sing > that testcase plus hackbench as efficacy booster produced lots of dying > box noise, but zero sneaky $subject instances before or after quash. Hohum, this morning I did hit.. 1. WARNING: CPU: 5 PID: 931 at kernel/sched/fair.c:6062 unthrottle_cfs_rq+= 0x4c3/0x4d0 2. WARNING: CPU: 0 PID: 786 at kernel/sched/fair.c:704 update_entity_lag+0= x79/0x90 3. NULL dereference in pick_next_entity() ..instead of brick, workqueue stall etc. Twice. Not that it matters. I was only mucking about with it because I was curious whether telling LB to stop moving sched_delayed tasks about would matter. (nope) -Mike