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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 9l+TzpsJG0E94wYIiBp9EjhHwypOt+q9xOyLgeWqk0O9HzJOt+ADZ183eZ6v8eIFkLos5ntmf5PJbfIEZHU4nh/fKRBYCI9F1cNUZI5GibZkH1XI9LzOMD6JLFlNMgYHWZbSgO/IzOPcZbvWezsWq0Oy6f95iv4K0nNBAQycCx9+6MBJk/nVwmbEcGRu6sC5VZS7vX82tdL4FJjEa0DNxftw+jQVkoQi8EmyjKpbEznqcaGlc7arLfGoWWAFcgsBYOChKhiv2ToLeo5Oj/tbRqmQqJFQ2yUnpao7SVkd3kJQjXd+DuN0+6IpieMGsnGOtNESf53BKLo+mlT7i1WcHCJqNXsAOb6QMAMGDU8oPPloGPiAMI7JbKCLrQcDgDRwAVefH2omJV/i+aj/tVkeaVpzHca+DbTQwiShp0D3T3/kDqDWC5iqLIJDGJiJOpVT X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Feb 2026 06:46:01.6179 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 8647b875-ba19-4a37-36c5-08de62efe54b X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SN1PEPF000252A0.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB6186 Hello Peter, On 1/30/2026 3:04 PM, Peter Zijlstra wrote: > Two issues related to reweight_entity() were raised; poking at all that got me > these patches. > > They're in queue.git/sched/core and I spend most of yesterday staring at traces > trying to find anything wrong. So far, so good. > > Please test. I put this on top of tip:sched/urgent + tip:sched/core which contains Ingo's cleanup of removing the union and at some point in the benchmark run I hit: BUG: kernel NULL pointer dereference, address: 0000000000000051 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD c153802067 P4D c1750e7067 PUD c16067e067 PMD 0 Oops: Oops: 0000 [#1] SMP NOPTI CPU: 200 UID: 1000 PID: 92850 Comm: schbench Not tainted 6.19.0-rc6-peterz-eevdf-fix+ #4 PREEMPT(full) Hardware name: ... (Zen4c server) RIP: 0010:pick_task_fair+0x3c/0x130 Code: ... RSP: 0000:ff5cc03f25ecfd58 EFLAGS: 00010046 RAX: 0000000000000000 RBX: ff3087d6eb032380 RCX: 00000000056ae402 RDX: fffe78b16a6ed620 RSI: fffe790e92f4c046 RDI: 00027caa24e6c3ee RBP: 0000000000000000 R08: 0000000000000002 R09: 0000000000000002 R10: 0000086bfb248f00 R11: 0000000000000438 R12: ff3087d6eb032480 R13: ff5cc03f25ecfea0 R14: ff3087d6eb032380 R15: ff3087d6eb032380 FS: 00007f176438a640(0000) GS:ff3087d73d0e2000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000051 CR3: 000000c0d275c048 CR4: 0000000000f71ef0 PKRU: 55555554 Call Trace: pick_next_task_fair+0x46/0x7b0 ? task_tick_fair+0xf1/0x8b0 ? perf_event_task_tick+0x5e/0xc0 __pick_next_task+0x41/0x1d0 __schedule+0x26e/0x17a0 ? srso_alias_return_thunk+0x5/0xfbef5 ? timerqueue_add+0x9f/0xc0 ? __hrtimer_run_queues+0x139/0x240 ? ktime_get+0x3f/0xf0 ? srso_alias_return_thunk+0x5/0xfbef5 ? srso_alias_return_thunk+0x5/0xfbef5 ? srso_alias_return_thunk+0x5/0xfbef5 ? clockevents_program_event+0xaa/0x100 schedule+0x27/0xd0 irqentry_exit+0x2a8/0x610 ? srso_alias_return_thunk+0x5/0xfbef5 ? __irq_exit_rcu+0x3f/0xf0 asm_sysvec_apic_timer_interrupt+0x1a/0x20 RIP: 0033:0x7f17f2498e58 Code: ... RSP: 002b:00007f1764389d48 EFLAGS: 00000202 RAX: 0000000000000010 RBX: 00000000000000c8 RCX: 00007f17f24e57f8 RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000014cd2820 RBP: 0000000014cd2820 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000293 R12: 00007f1764389e00 R13: 00007f176439fed0 R14: 0000000000002a40 R15: 00007f17b414c778 Modules linked in: ... CR2: 0000000000000051 ---[ end trace 0000000000000000 ]--- RIP points to "se->sched_delayed" dereference in pick_task_fair(): $ scripts/faddr2line vmlinux pick_task_fair+0x3c/0x130 pick_task_fair+0x3c/0x130: pick_next_entity at kernel/sched/fair.c:5648 (inlined by) pick_task_fair at kernel/sched/fair.c:9061 $ sed -n '5645,5651p' kernel/sched/fair.c struct sched_entity *se; se = pick_eevdf(cfs_rq); if (se->sched_delayed) { dequeue_entities(rq, se, DEQUEUE_SLEEP | DEQUEUE_DELAYED); /* * Must not reference @se again, see __block_task(). so something went sideways with the avg_vruntime calculation I presume. I'm rerunning with the PARANOID_AVG feat now. Just re-running the particular schbench variant hasn't crashed the kernel in the half hour it has been running so I've re-triggered the same set of benchmarks to see if flipping PARANOID_AVG makes any difference. If you have a debug patch somewhere that you would like data on this run from, please do let me know, else I plan on capturing the rq state at the time of crash (cfs_rq walk, dumping all the vruntimes of all the queued entities). -- Thanks and Regards, Prateek