syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (1 ticks this GP) idle=b37c/1/0x4000000000000000 softirq=24753/24753 fqs=0
rcu: 	(detected by 1, t=10502 jiffies, g=12649, q=206 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 6903 Comm: syz.0.231 Not tainted 6.15.0-rc4-syzkaller-00147-gebd297a2affa #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
RIP: 0010:preempt_count arch/x86/include/asm/preempt.h:27 [inline]
RIP: 0010:check_kcov_mode kernel/kcov.c:183 [inline]
RIP: 0010:write_comp_data+0x11/0x90 kernel/kcov.c:246
Code: cc cc 0f 1f 80 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 49 89 d2 49 89 f8 49 89 f1 65 48 8b 15 97 b3 e8 11 <65> 8b 05 a8 b3 e8 11 a9 00 01 ff 00 74 1d f6 c4 01 74 67 a9 00 00
RSP: 0018:ffffc90000007e00 EFLAGS: 00000046
RAX: 0000000000000000 RBX: ffff888036438340 RCX: ffffffff81a858e5
RDX: ffff888031dea440 RSI: 0000000000000000 RDI: 0000000000000001
RBP: ffff8880b8427940 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: ffff8880b8427840 R15: 0000000000000000
FS:  00007f0fc4c806c0(0000) GS:ffff8881249e2000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000006040 CR3: 00000000791ad000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 __remove_hrtimer+0xa5/0x290 kernel/time/hrtimer.c:1121
 __run_hrtimer kernel/time/hrtimer.c:1741 [inline]
 __hrtimer_run_queues+0x4f9/0xad0 kernel/time/hrtimer.c:1825
 hrtimer_interrupt+0x397/0x8e0 kernel/time/hrtimer.c:1887
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1038 [inline]
 __sysvec_apic_timer_interrupt+0x108/0x3f0 arch/x86/kernel/apic/apic.c:1055
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
 sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1049
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x31/0x80 kernel/locking/spinlock.c:194
Code: f5 53 48 8b 74 24 10 48 89 fb 48 83 c7 18 e8 e6 ce 28 f6 48 89 df e8 8e 22 29 f6 f7 c5 00 02 00 00 75 23 9c 58 f6 c4 02 75 37 <bf> 01 00 00 00 e8 e5 8e 19 f6 65 8b 05 1e a4 34 08 85 c0 74 16 5b
RSP: 0018:ffffc9000448f0b0 EFLAGS: 00000246
RAX: 0000000000000006 RBX: ffff8880b84256c0 RCX: 0000000000000006
RDX: 0000000000000000 RSI: ffffffff8dbe0861 RDI: ffffffff8bf47e20
RBP: 0000000000000287 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff9084fc17 R11: ffffffff9ad540f0 R12: 00000000ffffc3f1
R13: 0000000000000000 R14: ffff8880b84256c0 R15: 00000000ffffffff
 __mod_timer+0x8ed/0xd30 kernel/time/timer.c:1181
 blk_add_timer+0x229/0x2a0 block/blk-timeout.c:164
 blk_mq_start_request+0x191/0x900 block/blk-mq.c:1351
 null_queue_rq+0x512/0xfd0 drivers/block/null_blk/main.c:1682
 null_queue_rqs+0xe9/0x2f0 drivers/block/null_blk/main.c:1707
 __blk_mq_flush_plug_list block/blk-mq.c:2825 [inline]
 __blk_mq_flush_plug_list+0x97/0xc0 block/blk-mq.c:2820
 blk_mq_flush_plug_list+0x1698/0x1c70 block/blk-mq.c:2904
 __blk_flush_plug+0x2c4/0x4b0 block/blk-core.c:1220
 blk_finish_plug block/blk-core.c:1247 [inline]
 blk_finish_plug block/blk-core.c:1244 [inline]
 __submit_bio+0x545/0x690 block/blk-core.c:649
 __submit_bio_noacct_mq block/blk-core.c:722 [inline]
 submit_bio_noacct_nocheck+0x663/0xd30 block/blk-core.c:751
 submit_bio_noacct+0x50d/0x1ec0 block/blk-core.c:874
 submit_bh fs/buffer.c:2836 [inline]
 block_read_full_folio+0x4db/0x850 fs/buffer.c:2468
 filemap_read_folio+0xc5/0x2a0 mm/filemap.c:2401
 do_read_cache_folio+0x263/0x5c0 mm/filemap.c:3885
 read_mapping_folio include/linux/pagemap.h:995 [inline]
 read_part_sector+0xd4/0x310 block/partitions/core.c:722
 adfspart_check_ICS+0x93/0x940 block/partitions/acorn.c:360
 check_partition block/partitions/core.c:141 [inline]
 blk_add_partitions block/partitions/core.c:589 [inline]
 bdev_disk_changed+0x720/0x1520 block/partitions/core.c:693
 blkdev_get_whole+0x187/0x290 block/bdev.c:748
 bdev_open+0x2c7/0xe40 block/bdev.c:957
 bdev_file_open_by_dev block/bdev.c:1059 [inline]
 bdev_file_open_by_dev+0x182/0x210 block/bdev.c:1034
 disk_scan_partitions+0x1ed/0x320 block/genhd.c:374
 blkdev_common_ioctl+0x2f6/0x2480 block/ioctl.c:624
 blkdev_ioctl+0x1cb/0x6d0 block/ioctl.c:698
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl fs/ioctl.c:892 [inline]
 __x64_sys_ioctl+0x190/0x200 fs/ioctl.c:892
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f0fc3d8e969
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:00007f0fc4c80038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f0fc3fb5fa0 RCX: 00007f0fc3d8e969
RDX: 0000000000000000 RSI: 000000000000125f RDI: 0000000000000007
RBP: 00007f0fc3e10ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f0fc3fb5fa0 R15: 00007fff3a880a08
 </TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10501 jiffies! g12649 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=0 timer-softirq=7028
rcu: rcu_preempt kthread starved for 10502 jiffies! g12649 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:27304 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x116f/0x5de0 kernel/sched/core.c:6767
 __schedule_loop kernel/sched/core.c:6845 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:6860
 schedule_timeout+0x123/0x290 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x1ea/0xb00 kernel/rcu/tree.c:2046
 rcu_gp_kthread+0x270/0x380 kernel/rcu/tree.c:2248
 kthread+0x3c2/0x780 kernel/kthread.c:464
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>