INFO: rcu detected stall in preempt_schedule_thunk (4)

Status: upstream: reported syz repro on 2026/06/30 21:43
Subsystems: kernel
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+5949336bc3b8e70e1325@syzkaller.appspotmail.com
First crash: 55d, last: 1d06h
Cause bisection: failed (error log, bisect log)
  
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ID Workflow Result Correct Bug Created Started Finished Revision
87945e20 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ INFO: rcu detected stall in preempt_schedule_thunk (4) 2026/06/26 00:00 2026/06/26 00:00 2026/06/26 00:37 7ff32d8b
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Title Replies (including bot) Last reply
[syzbot] [kernel?] INFO: rcu detected stall in preempt_schedule_thunk (4) 0 (1) 2026/06/30 21:43
▶ ▼ Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in preempt_schedule_thunk 1 1 823d 823d 0/3 auto-obsoleted due to no activity on 2024/08/25 23:34
linux-6.6 INFO: rcu detected stall in preempt_schedule_thunk (3) 1 3 3d05h 57d 0/2 upstream: reported on 2026/06/22 06:08
linux-6.6 INFO: rcu detected stall in preempt_schedule_thunk 1 1 340d 340d 0/2 auto-obsoleted due to no activity on 2025/12/21 20:33
linux-6.6 INFO: rcu detected stall in preempt_schedule_thunk (2) 1 1 230d 230d 0/2 auto-obsoleted due to no activity on 2026/04/10 03:12
upstream INFO: rcu detected stall in preempt_schedule_thunk kernel 1 4 745d 786d 0/29 auto-obsoleted due to no activity on 2024/11/01 23:14
upstream INFO: rcu detected stall in preempt_schedule_thunk (3) kernel 1 1 223d 223d 0/29 auto-obsoleted due to no activity on 2026/04/07 23:53
upstream INFO: rcu detected stall in preempt_schedule_thunk (2) kernel 1 2 608d 653d 0/29 auto-obsoleted due to no activity on 2025/03/18 05:25
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/07/19 02:46 32m retest repro upstream log

Sample crash report:
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>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/30 08:38 upstream dc59e4fea9d8 fff8d0a0 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in preempt_schedule_thunk
2026/06/24 02:49 upstream f31c00c377cc 042555ff .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in preempt_schedule_thunk
2026/08/17 20:04 net ad27ed7d2309 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in preempt_schedule_thunk
* Struck through repros no longer work on HEAD.