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List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6e02:1a45:b0:3ee:7c7a:c89c with SMTP id e9e14a558f8ab-3f40085fa09mr136295675ab.14.1756689275689; Sun, 31 Aug 2025 18:14:35 -0700 (PDT) Date: Sun, 31 Aug 2025 18:14:35 -0700 In-Reply-To: <672f1c3a.050a0220.138bd5.003a.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <68b4f37b.a00a0220.1337b0.003d.GAE@google.com> Subject: Re: [syzbot] [kernel?] INFO: rcu detected stall in schedule_timeout (7) From: syzbot To: anna-maria@linutronix.de, bp@alien8.de, dave.hansen@linux.intel.com, frederic@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, mingo@redhat.com, syzkaller-bugs@googlegroups.com, tglx@linutronix.de, x86@kernel.org Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: 7fa4d8dc380f Add linux-next specific files for 20250821 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=11b0a1f0580000 kernel config: https://syzkaller.appspot.com/x/.config?x=ae76068823a236b3 dashboard link: https://syzkaller.appspot.com/bug?extid=8926d1b522e7194a4b3e compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12cf5a62580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15b0a1f0580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/63178c6ef3f8/disk-7fa4d8dc.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/c5c27b0841e0/vmlinux-7fa4d8dc.xz kernel image: https://storage.googleapis.com/syzbot-assets/9a8832715cca/bzImage-7fa4d8dc.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+8926d1b522e7194a4b3e@syzkaller.appspotmail.com rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: (detected by 0, t=10502 jiffies, g=8469, q=411 ncpus=2) rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294959250-4294948747), jiffies_till_next_fqs=1, root ->qsmask 0x0 rcu: rcu_preempt kthread starved for 10504 jiffies! g8469 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0 rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior. rcu: RCU grace-period kthread stack dump: task:rcu_preempt state:R running task stack:26728 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00004000 Call Trace: context_switch kernel/sched/core.c:5357 [inline] __schedule+0x1798/0x4cc0 kernel/sched/core.c:6961 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7288 irqentry_exit+0x6f/0x90 kernel/entry/common.c:197 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 RIP: 0010:timer_destroy_on_stack+0x4/0x20 kernel/time/timer.c:822 Code: 80 e1 07 80 c1 03 38 c1 7c b4 e8 f7 63 76 00 eb ad 0f 1f 44 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa <53> 48 89 fb e8 43 b9 12 00 48 89 df 48 c7 c6 60 e2 ac 8b 5b e9 c3 RSP: 0018:ffffc90000157a38 EFLAGS: 00000246 RAX: 0000000000000000 RBX: 00000000ffffb78c RCX: ffff88801d29da00 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffc90000157a60 RBP: ffffc90000157b30 R08: ffffffff8fe52d37 R09: 1ffffffff1fca5a6 R10: dffffc0000000000 R11: fffffbfff1fca5a7 R12: 1ffff9200002af48 R13: 1ffffffff1c42240 R14: ffffc90000157a60 R15: dffffc0000000000 schedule_timeout+0x13b/0x270 kernel/time/sleep_timeout.c:103 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x47c/0x820 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 rcu: Stack dump where RCU GP kthread last ran: CPU: 0 UID: 0 PID: 6118 Comm: syz.1.31 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 RIP: 0010:__local_bh_disable_ip+0x44/0x190 kernel/softirq.c:329 Code: 89 f3 65 48 8b 05 4c b6 5f 11 48 89 44 24 68 49 bf 00 00 00 00 00 fc ff df 48 c7 04 24 b3 8a b5 41 48 c7 44 24 08 5d 5b ce 8d <48> c7 44 24 10 b0 09 86 81 49 89 e4 49 c1 ec 03 48 b8 f1 f1 f1 f1 RSP: 0018:ffffc90003597c80 EFLAGS: 00000282 RAX: 63bb6213f70ec600 RBX: 0000000000000200 RCX: ffff88807d190000 RDX: 0000000000000000 RSI: 0000000000000200 RDI: ffffffff81699312 RBP: ffffc90003597d30 R08: 0000000000000001 R09: 0000000000000000 R10: dffffc0000000000 R11: fffff520006b2fc6 R12: ffff88807d191940 R13: ffff88807d19002c R14: dffffc0000000000 R15: dffffc0000000000 FS: 00007fe55f3cd6c0(0000) GS:ffff8881257c4000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000200000000058 CR3: 00000000741c6000 CR4: 00000000003526f0 Call Trace: local_bh_disable include/linux/bottom_half.h:20 [inline] fpregs_lock arch/x86/include/asm/fpu/api.h:69 [inline] fpu__clear_user_states+0x90/0x350 arch/x86/kernel/fpu/core.c:813 handle_signal arch/x86/kernel/signal.c:310 [inline] arch_do_signal_or_restart+0x452/0x750 arch/x86/kernel/signal.c:339 exit_to_user_mode_loop+0x75/0x130 kernel/entry/common.c:40 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline] syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline] do_syscall_64+0x2bd/0xfa0 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fe55e5b7320 Code: 83 c0 16 83 e0 f7 74 12 50 48 8d 3d 4a 3e 08 00 e8 f5 8f f8 ff 0f 1f 44 00 00 c3 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 <83> ff 21 74 0b c3 66 2e 0f 1f 84 00 00 00 00 00 55 53 48 89 f3 48 RSP: 002b:00007fe55f3ccb38 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: 0000000000000000 RBX: 00007fe55e7c5fa8 RCX: 00007fe55e58ebe9 RDX: 00007fe55f3ccb40 RSI: 00007fe55f3ccc70 RDI: 0000000000000021 RBP: 00007fe55e7c5fa0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fe55e7c6038 R14: 00007ffe9f8ccd20 R15: 00007ffe9f8cce08 --- If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing.