[syzbot] [kernel?] INFO: rcu detected stall in preempt_schedule_thunk (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dc59e4fea9d8 Linux 7.2-rc1
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=178cedfe580000
kernel config: https://syzkaller.appspot.com/x/.config?x=77808e35144e725c
dashboard link: https://syzkaller.appspot.com/bug?extid=5949336bc3b8e70e1325
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16850e1c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9911e5707540/disk-dc59e4fe.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bb0af0bc6e42/vmlinux-dc59e4fe.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b7ca0661e875/bzImage-dc59e4fe.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+594933...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: (detected by 0, t=10502 jiffies, g=15901, q=654 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294968259-4294957756), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10504 jiffies! g15901 f0x2 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:28984 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5510 [inline]
__schedule+0x125c/0x6730 kernel/sched/core.c:7234
__schedule_loop kernel/sched/core.c:7311 [inline]
schedule+0xdd/0x2c0 kernel/sched/core.c:7326
schedule_timeout+0x127/0x280 kernel/time/sleep_timeout.c:99
rcu_gp_fqs_loop+0x1a9/0x900 kernel/rcu/tree.c:2123
rcu_gp_kthread+0x179/0x230 kernel/rcu/tree.c:2325
kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 50 Comm: kworker/u9:0 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Workqueue: krxrpcd rxrpc_peer_keepalive_worker
RIP: 0010:asm_sysvec_apic_timer_interrupt+0x0/0x20 arch/x86/include/asm/idtentry.h:674
Code: 16 b1 9c 0a e9 81 06 00 00 90 f3 0f 1e fa 0f 01 ca fc 6a ff e8 31 05 00 00 48 89 c4 48 89 e7 e8 26 b0 9c 0a e9 61 06 00 00 90 <f3> 0f 1e fa 0f 01 ca fc 6a ff e8 11 05 00 00 48 89 c4 48 89 e7 e8
RSP: 0018:ffffc90000bb78b8 EFLAGS: 00000006
RAX: 000000000037eeeb RBX: ffff88801d35a540 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8e15d8c3 RDI: ffff88801d35bc38
RBP: ffffc90000bb7940 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff8880274d4a80
R13: 0000000000000000 R14: ffffffff90fbe664 R15: ffff8880b853b4c0
FS: 0000000000000000(0000) GS:ffff8881241e0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000058 CR3: 0000000071842000 CR4: 00000000003526f0
Call Trace:
<TASK>
RIP: 0010:finish_task_switch.isra.0+0x2cd/0x10c0 kernel/sched/core.c:5361
Code: ab 0a 00 00 41 c7 87 20 0e 00 00 00 00 00 00 0f 1f 44 00 00 49 8d 7f 48 e8 b0 a4 ca 09 e8 4b ad 3c 00 fb 48 8d bb f8 16 00 00 <48> b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 0f b6 04 02 84
RSP: 0018:ffffc90000bb78e8 EFLAGS: 00000206
context_switch kernel/sched/core.c:5513 [inline]
__schedule+0x1264/0x6730 kernel/sched/core.c:7234
preempt_schedule_irq+0x50/0x90 kernel/sched/core.c:7556
irqentry_exit_to_kernel_mode_preempt include/linux/irq-entry-common.h:468 [inline]
irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:539 [inline]
irqentry_exit+0x205/0xa00 kernel/entry/common.c:167
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:constant_test_bit arch/x86/include/asm/bitops.h:202 [inline]
RIP: 0010:arch_test_bit arch/x86/include/asm/bitops.h:232 [inline]
RIP: 0010:tif_test_bit include/linux/thread_info.h:199 [inline]
RIP: 0010:tif_need_resched include/linux/thread_info.h:215 [inline]
RIP: 0010:need_resched include/linux/sched.h:2258 [inline]
RIP: 0010:preempt_schedule_common+0x49/0xc0 kernel/sched/core.c:7421
Code: c3 65 ff 05 79 ee 95 08 65 8b 05 72 ee 95 08 25 ff ff ff 7f 83 f8 01 74 27 bf 01 00 00 00 e8 de 93 ff ff 65 ff 0d 57 ee 95 08 <80> 3b 00 75 55 48 8b 45 00 a8 10 75 ca 5b 5d 41 5c c3 cc cc cc cc
RSP: 0018:ffffc90000bb7bc0 EFLAGS: 00000286
RAX: 0000000000000000 RBX: ffffed1003a6b4a8 RCX: 1ffff92000176f65
RDX: 0000000000000000 RSI: ffffffff8c3e9b00 RDI: ffffffff8e417928
RBP: ffff88801d35a540 R08: 0000000000000000 R09: fffffbfff21f7652
R10: ffffffff90fbb297 R11: 0000000000000000 R12: ffffffff81759c96
R13: 0000000000000000 R14: ffffffff90fbe664 R15: 0000000000000001
preempt_schedule_thunk+0x16/0x40 arch/x86/entry/thunk.S:12
__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:188 [inline]
_raw_spin_unlock_irq+0x44/0x50 kernel/locking/spinlock.c:206
process_one_work+0x871/0x1940 kernel/workqueue.c:3291
process_scheduled_works kernel/workqueue.c:3405 [inline]
worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>


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