syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P20/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=94941, q=249 ncpus=2)
task:rcuc/0          state:R  running task     stack:24552 pid:20    tgid:20    ppid:2      task_flags:0x4208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x145f/0x5070 kernel/sched/core.c:6863
 preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7190
 irqentry_exit+0x5d8/0x660 kernel/entry/common.c:216
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:rcu_cblist_dequeue+0x6f/0xc0 kernel/rcu/rcu_segcblist.c:75
Code: 80 3c 20 00 74 08 4c 89 ff e8 9d 81 7a 00 49 ff 0f 4c 89 f0 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 84 81 7a 00 4d 8b 3e <43> 80 7c 25 00 00 74 08 48 89 df e8 61 82 7a 00 4c 89 3b 4d 85 ff
RSP: 0018:ffffc90000197b10 EFLAGS: 00000246
RAX: 1ffff110048fcb22 RBX: ffffc90000197c60 RCX: 0000000000ced402
RDX: 000000007a4b5786 RSI: ffffffff8b3f57c0 RDI: ffffc90000197c60
RBP: ffffc90000197cf0 R08: ffffffff818503bc R09: ffffffff8d5ae940
R10: dffffc0000000000 R11: fffffbfff1db668f R12: dffffc0000000000
R13: 1ffff92000032f8c R14: ffff8880247e5910 R15: ffff8880247e5a00
 rcu_do_batch kernel/rcu/tree.c:2593 [inline]
 rcu_core kernel/rcu/tree.c:2857 [inline]
 rcu_cpu_kthread+0xaf3/0x1af0 kernel/rcu/tree.c:2945
 smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
rcu: rcu_preempt kthread starved for 10480 jiffies! g94941 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
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:27664 pid:18    tgid:18    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x145f/0x5070 kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6960
 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
 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+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 UID: 0 PID: 15718 Comm: syz.7.2731 Tainted: G             L      syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:preempt_count_add+0x8/0x190 kernel/sched/core.c:5714
Code: 3e 7e 91 00 eb 8c e9 f1 fe ff ff 0f 1f 80 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 41 57 41 56 <53> 49 bf 00 00 00 00 00 fc ff df 48 c7 c0 40 44 be 98 48 c1 e8 03
RSP: 0018:ffffc9000575fab0 EFLAGS: 00000286
RAX: 0000000080000000 RBX: 00000000000055f1 RCX: 0000000000000000
RDX: 0000000000000384 RSI: ffffffff8b3f57c0 RDI: 0000000000000001
RBP: 0000000000000001 R08: ffffffff8edb3477 R09: 1ffffffff1db668e
R10: dffffc0000000000 R11: ffffffff8ad032e0 R12: ffff88814676f930
R13: 1ffff11006bdeb8f R14: 00000384f7ba4752 R15: 0000000000000380
FS:  0000555590541500(0000) GS:ffff888126def000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000006332a000 CR4: 00000000003526f0
DR0: 0000000000800003 DR1: 00000000000001f5 DR2: 0000000000000483
DR3: 0000000000000007 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 delay_tsc+0x65/0xc0 arch/x86/lib/delay.c:79
 udelay include/asm-generic/delay.h:62 [inline]
 snd_timer_close_locked+0x30e/0x950 sound/core/timer.c:443
 snd_timer_close+0x48/0xf0 sound/core/timer.c:476
 snd_seq_timer_close+0xaa/0xf0 sound/core/seq/seq_timer.c:311
 queue_delete sound/core/seq/seq_queue.c:126 [inline]
 snd_seq_queue_delete+0x8d/0xf0 sound/core/seq/seq_queue.c:188
 delete_seq_queue sound/core/seq/oss/seq_oss_init.c:371 [inline]
 snd_seq_oss_release+0x1bc/0x2e0 sound/core/seq/oss/seq_oss_init.c:416
 odev_release+0x51/0xa0 sound/core/seq/oss/seq_oss.c:141
 __fput+0x45b/0xa80 fs/file_table.c:468
 task_work_run+0x1d4/0x260 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:44 [inline]
 exit_to_user_mode_loop+0xef/0x4e0 kernel/entry/common.c:75
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
 do_syscall_64+0x2b7/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd06e0ef749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe74f6ccf8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fd06e347da0 RCX: 00007fd06e0ef749
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007fd06e347da0 R08: 0000000000000208 R09: 0000001e74f6cfef
R10: 00007fd06e347cb0 R11: 0000000000000246 R12: 00000000001872b2
R13: 00007fd06e346270 R14: ffffffffffffffff R15: 00007ffe74f6ce10
 </TASK>