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bh=Pj/5V+KCxFaB+bX2qGxLv6ZfgJqgN4t6ZtBGPwG3SL8=; b=WvuEkTNcRtj6CpQgjjd0xbejILzhuTBB+q08LFJutgP1199WxSs0CBhIqGQUkP8gN3gQ0dQuMcFWQ5YcdO08Y/Vka/ejalybVsYE7r8zUqWR+5ole0CtZy3Pu2ThCHyZSKlroH3xth6Pf5uPWbTgp8cy3jHPcTJ6ddYxRq/9Ou0= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=os.amperecomputing.com; Received: from MW4PR01MB6436.prod.exchangelabs.com (2603:10b6:303:64::21) by DS1PR01MB9086.prod.exchangelabs.com (2603:10b6:8:221::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8207.12; Wed, 27 Nov 2024 05:56:39 +0000 Received: from MW4PR01MB6436.prod.exchangelabs.com ([fe80::77c9:9e36:e28e:7970]) by MW4PR01MB6436.prod.exchangelabs.com ([fe80::77c9:9e36:e28e:7970%4]) with mapi id 15.20.8207.010; Wed, 27 Nov 2024 05:56:39 +0000 From: Adam Li To: peterz@infradead.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org Cc: dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, linux-kernel@vger.kernel.org, patches@amperecomputing.com, cl@linux.com, christian.loehle@arm.com, vineethr@linux.ibm.com, Adam Li Subject: [PATCH v2 0/3] sched/fair: Fix NEXT_BUDDY panic and warning Date: Wed, 27 Nov 2024 05:56:07 +0000 Message-Id: <20241127055610.7076-1-adamli@os.amperecomputing.com> X-Mailer: git-send-email 2.25.1 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: SI2PR01CA0036.apcprd01.prod.exchangelabs.com (2603:1096:4:192::22) To MW4PR01MB6436.prod.exchangelabs.com (2603:10b6:303:64::21) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MW4PR01MB6436:EE_|DS1PR01MB9086:EE_ X-MS-Office365-Filtering-Correlation-Id: ba22d5c4-abad-48dc-ef77-08dd0ea8425b X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|52116014|7416014|376014|38350700014; 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The kernel panic is triggered in pick_next_entity() if pick_eevdf() returns NULL. In patch 1 ("Fix warning if NEXT_BUDDY enabled"), if sched_delayed is set we do not set next buddy. After the patch, kernel warning, rcu stall and panic disappear. However to avoid panic, we still check return value of pick_eevdf(). The 'last' and 'skip' buddy are obsoleted by EEVDF. Update the comments in pick_next_entity(). Detail log bellow: [ 124.972623] ------------[ cut here ]------------ [ 124.977300] cfs_rq->next->sched_delayed [ 124.977310] WARNING: CPU: 51 PID: 2150 at kernel/sched/fair.c:5621 pick_task_fair+0x130/0x150 [ 125.049547] CPU: 51 UID: 0 PID: 2150 Comm: kworker/51:1 Tainted: G E 6.12.0.adam+ #1 [ 125.058678] Tainted: [E]=UNSIGNED_MODULE [ 125.062591] Hardware name: IEI NF5280R7/Mitchell MB, BIOS 4.4.3.1 10/16/2024 [ 125.069629] Workqueue: 0x0 (mm_percpu_wq) [ 125.073721] pstate: 634000c9 (nZCv daIF +PAN -UAO +TCO +DIT -SSBS BTYPE=--) [ 125.080671] pc : pick_task_fair+0x130/0x150 [ 125.084841] lr : pick_task_fair+0x130/0x150 [ 125.089013] sp : ffff8000ab41bc10 [ 125.092315] x29: ffff8000ab41bc10 x28: 0000000000000000 x27: 0000000000000000 [ 125.099440] x26: ffff000123bd8788 x25: 0000000000000402 x24: 0000000000000001 [ 125.106565] x23: ffff000123bd8000 x22: ffff007dfef5cd00 x21: ffff007dfef5cd80 [ 125.113689] x20: ffff007dfef5cd80 x19: ffff2001ab20a780 x18: 0000000000000006 [ 125.120815] x17: 0000000000000000 x16: 0000000000000000 x15: ffff8000ab41b5e0 [ 125.127938] x14: 0000000000000000 x13: 646579616c65645f x12: 64656863733e2d74 [ 125.135062] x11: fffffffffc000000 x10: ffff207dfac9b420 x9 : ffff80008014ed60 [ 125.142185] x8 : 00000000ffdfffff x7 : ffff207dfac80000 x6 : 000000000000122c [ 125.149309] x5 : ffff007dfef49408 x4 : 40000000ffe0122c x3 : ffff807d7d673000 [ 125.156433] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff000123bd8000 [ 125.163561] Call trace: [ 125.165996] pick_task_fair+0x130/0x150 (P) [ 125.170167] pick_task_fair+0x130/0x150 (L) [ 125.174338] pick_next_task_fair+0x48/0x3c0 [ 125.178512] __pick_next_task+0x4c/0x220 [ 125.182426] pick_next_task+0x44/0x980 [ 125.186163] __schedule+0x3d0/0x628 [ 125.189645] schedule+0x3c/0xe0 [ 125.192776] worker_thread+0x1a4/0x368 [ 125.196516] kthread+0xfc/0x110 [ 125.199647] ret_from_fork+0x10/0x20 [ 125.203213] ---[ end trace 0000000000000000 ]--- [ 125.207818] ------------[ cut here ]------------ [ 211.151849] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: [ 211.159759] rcu: (detected by 141, t=15003 jiffies, g=5629, q=26516 ncpus=384) [ 211.169780] rcu: All QSes seen, last rcu_preempt kthread activity 15002 (4294943634-4294928632), jiffies_till_next_fqs=2, root ->qsmask 0x0 [ 211.185062] rcu: rcu_preempt kthread timer wakeup didn't happen for 15004 jiffies! g5629 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 [ 211.199043] rcu: Possible timer handling issue on cpu=352 timer-softirq=1091 [ 211.208943] rcu: rcu_preempt kthread starved for 15012 jiffies! g5629 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=352 [ 211.222141] rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior. [ 211.234037] rcu: RCU grace-period kthread stack dump: [ 211.241854] task:rcu_preempt state:R running task stack:0 pid:17 tgid:17 ppid:2 flags:0x00000008 [ 211.255487] Call trace: [ 211.260698] __switch_to+0xf0/0x150 (T) [ 211.267299] __schedule+0x238/0x628 [ 211.273553] schedule+0x3c/0xe0 [ 211.279459] schedule_timeout+0x88/0x108 [ 211.286147] rcu_gp_fqs_loop+0x158/0x4d0 [ 211.292835] rcu_gp_kthread+0x164/0x198 [ 211.299436] kthread+0xfc/0x110 [ 211.305342] ret_from_fork+0x10/0x20 [ 211.311684] rcu: Stack dump where RCU GP kthread last ran: [ 211.319940] Sending NMI from CPU 141 to CPUs 352: [ 211.327411] NMI backtrace for cpu 352 [ 211.333835] CPU: 352 UID: 0 PID: 0 Comm: swapper/352 Tainted: G W E 6.12.0.adam+ #1 [ 211.345466] Tainted: [W]=WARN, [E]=UNSIGNED_MODULE [ 211.353021] Hardware name: IEI NF5280R7/Mitchell MB, BIOS 4.4.3.1 10/16/2024 [ 211.362834] pstate: 63400009 (nZCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--) [ 211.372557] pc : cpuidle_enter_state+0xcc/0x4f0 [ 211.379851] lr : cpuidle_enter_state+0xc0/0x4f0 [ 211.387147] sp : ffff8000878c3d70 [ 211.393226] x29: ffff8000878c3d70 x28: 0000000000000000 x27: 0000000000000000 [ 211.403125] x26: 0000000000000000 x25: 0000000000000000 x24: 0000003133e26b84 [ 211.413023] x23: 0000000000000000 x22: ffff800082092d98 x21: 00000031341844e8 [ 211.422922] x20: 0000000000000000 x19: ffff20011d459800 x18: 0000000000000000 [ 211.432820] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 [ 211.442719] x14: 0000000000000000 x13: ffff800081dcf030 x12: 0000000000000001 [ 211.452619] x11: 0000003131433c14 x10: 071c71c71c71c71c x9 : ffff8000810b5900 [ 211.462517] x8 : 00000000003bf790 x7 : ffff207e031d57e4 x6 : 0000002023a22338 [ 211.472416] x5 : 1fffffffffffffff x4 : 0000000000000015 x3 : 000000000030e5a8 [ 211.482314] x2 : ffffa07d818ed000 x1 : ffff207e031d6d00 x0 : 0000000000000000 [ 211.492213] Call trace: [ 211.497426] cpuidle_enter_state+0xcc/0x4f0 (P) [ 211.504719] cpuidle_enter_state+0xc0/0x4f0 (L) [ 211.512013] cpuidle_enter+0x40/0x60 [ 211.518351] cpuidle_idle_call+0x130/0x1c8 [ 211.525212] do_idle+0xec/0xf8 [ 211.531033] cpu_startup_entry+0x40/0x50 [ 211.537719] secondary_start_kernel+0xe0/0x120 [ 211.544926] __secondary_switched+0xc0/0xc8 [ 297.371198] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000051 [ 297.406112] CPU: 116 UID: 0 PID: 10328 Comm: Grizzly-worker( Tainted: G W E 6.12.0.adam+ #1 [ 297.414884] Mem abort info: [ 297.424437] Tainted: [W]=WARN, [E]=UNSIGNED_MODULE [ 297.427219] ESR = 0x0000000096000005 [ 297.431997] Hardware name: IEI NF5280R7/Mitchell MB, BIOS 4.4.3.1 10/16/2024 [ 297.435734] EC = 0x25: DABT (current EL), IL = 32 bits [ 297.442770] pstate: a34000c9 (NzCv daIF +PAN -UAO +TCO +DIT -SSBS BTYPE=--) [ 297.448069] SET = 0, FnV = 0 [ 297.455018] pc : pick_task_fair+0x50/0x150 [ 297.458060] EA = 0, S1PTW = 0 [ 297.462144] lr : pick_task_fair+0x50/0x150 [ 297.465274] FSC = 0x05: level 1 translation fault [ 297.469358] sp : ffff800101d93ae0 [ 297.474223] Data abort info: [ 297.477526] x29: ffff800101d93ae0 [ 297.480395] ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000 [ 297.480395] x28: 0000000000000009 [ 297.483703] x27: 0000000000000000 [ 297.489177] CM = 0, WnR = 0, TnD = 0, TagAccess = 0 [ 297.492567] [ 297.495956] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [ 297.500996] x26: ffff006da4381b08 [ 297.502477] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000198b3b000 [ 297.507777] x25: 0000000000000080 [ 297.511080] [0000000000000051] pgd=08000001c0636403 [ 297.517509] x24: 0000000000000001 [ 297.520899] , p4d=08000001c0636403 [ 297.525765] [ 297.529155] , pud=0000000000000000 [ 297.532545] x23: ffff006da4381380 [ 297.534025] [ 297.537415] x22: ffff007dff7fed00 x21: ffff007dff7fed80 [ 297.547496] x20: ffff000167f60c00 x19: 0000000000000000 x18: 0000000000000006 [ 297.554621] x17: ffff8000820b3be8 x16: 0000000087c17f9e x15: ffff800083d53690 [ 297.561745] x14: 0000000000000004 x13: ffff800081df4ac8 x12: 0000000000000000 [ 297.568868] x11: ffff200111a3f0b0 x10: ffff200111a3efc8 x9 : ffff800080109e48 [ 297.575992] x8 : 00000000000000b8 x7 : 0000000000000074 x6 : 0000000000000002 [ 297.583115] x5 : 0000000000000002 x4 : 0000000000000002 x3 : 0000000000000000 [ 297.590239] x2 : fffffffffffffff0 x1 : 0000000000000000 x0 : 0000000000000000 [ 297.597362] Call trace: [ 297.599795] pick_task_fair+0x50/0x150 (P) [ 297.603879] pick_task_fair+0x50/0x150 (L) [ 297.607963] pick_next_task_fair+0x30/0x3c0 [ 297.612134] __pick_next_task+0x4c/0x220 [ 297.616045] pick_next_task+0x44/0x980 [ 297.619782] __schedule+0x3d0/0x628 [ 297.623259] do_task_dead+0x50/0x60 [ 297.626736] do_exit+0x28c/0x410 [ 297.629955] do_group_exit+0x3c/0xa0 [ 297.633518] get_signal+0x8c4/0x8d0 [ 297.636996] do_signal+0x9c/0x270 [ 297.640299] do_notify_resume+0xe0/0x198 [ 297.644212] el0_svc+0xf4/0x170 [ 297.647342] el0t_64_sync_handler+0x10c/0x138 [ 297.651687] el0t_64_sync+0x1ac/0x1b0 [ 297.655339] Code: d503201f 1400002a aa1403e0 97ffda0b (39414401) [ 297.661439] ---[ end trace 0000000000000000 ]--- [ 297.726593] Kernel panic - not syncing: Oops: Fatal exception v2: Follow Christian Loehle's suggestion, revise commit message. Add patch to check return value of pick_eevdf() in pick_next_entity(). v1: https://lore.kernel.org/all/20241125021222.356881-1-adamli@os.amperecomputing.com/ Adam Li (3): sched/fair: Fix warning if NEXT_BUDDY enabled sched/fair: Fix panic if pick_eevdf() returns NULL sched/fair: Update comments regarding last and skip buddy kernel/sched/fair.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-) -- 2.25.1