INFO: task hung in synchronize_rcu

Status: upstream: reported on 2025/10/30 17:16
Reported-by: syzbot+6d7cbd2cd15cb48338f3@syzkaller.appspotmail.com
First crash: 315d, last: 4d15h
▶ ▼ Similar bugs (16)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in synchronize_rcu (3) 1 syz, C done done 374 1304d 2241d 22/29 fixed on 2023/02/24 13:50
linux-6.1 INFO: task hung in synchronize_rcu origin:lts-only 1 syz, C unreliable 200 23h34m 1259d 0/3 upstream: reported C repro on 2023/04/01 04:49
android-6-12 INFO: task hung in synchronize_rcu (3) 1 3 35d 62d 0/1 premoderation: reported on 2026/07/10 14:29
android-49 INFO: task hung in synchronize_rcu 1 1 2477d 2477d 0/3 auto-closed as invalid on 2020/03/28 16:57
linux-4.14 INFO: task hung in synchronize_rcu vfs 1 syz, C error 162 1318d 2500d 0/1 upstream: reported C repro on 2019/11/07 04:32
linux-4.19 INFO: task hung in synchronize_rcu 1 syz, C error 70 1307d 2498d 0/1 upstream: reported C repro on 2019/11/08 21:27
linux-5.15 INFO: task hung in synchronize_rcu 1 1 1244d 1244d 0/3 auto-obsoleted due to no activity on 2023/08/14 02:05
android-6-12 INFO: task hung in synchronize_rcu 1 41 302d 426d 0/1 auto-obsoleted due to no activity on 2026/01/01 15:51
linux-5.15 INFO: task hung in synchronize_rcu (3) origin:lts-only 1 syz, C error 56 4d03h 777d 0/3 upstream: reported C repro on 2024/07/26 03:55
upstream INFO: task hung in synchronize_rcu 1 syz done 1206 2477d 2503d 14/29 fixed on 2019/11/29 15:48
upstream INFO: task hung in synchronize_rcu (4) prio:high net 1 syz, C done error 4605 11m 1226d 0/29 upstream: reported C repro on 2023/05/04 02:01
linux-5.15 INFO: task hung in synchronize_rcu (2) 1 1 932d 932d 0/3 auto-obsoleted due to no activity on 2024/05/31 13:53
android-414 INFO: task hung in synchronize_rcu 1 1 2495d 2495d 0/1 auto-closed as invalid on 2020/03/10 10:42
upstream INFO: task hung in synchronize_rcu (2) trace 1 8 2476d 2477d 0/29 closed as invalid on 2019/11/30 16:54
android-6-12 INFO: task hung in synchronize_rcu (2) 1 5 167d 208d 0/1 auto-obsoleted due to no activity on 2026/06/25 10:28
upstream INFO: task hung in rtnetlink_rcv_msg net 1 syz, C inconclusive inconclusive 1970 794d 2757d 26/29 fixed on 2024/07/09 19:14

Sample crash report:
INFO: task rcu_tasks_trace:15 blocked for more than 141 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:rcu_tasks_trace state:D stack:27368 pid:15    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6834
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0x673/0xc80 kernel/locking/mutex.c:747
 exp_funnel_lock kernel/rcu/tree_exp.h:324 [inline]
 synchronize_rcu_expedited+0x3da/0x880 kernel/rcu/tree_exp.h:1004
 synchronize_rcu+0x142/0x3e0 kernel/rcu/tree.c:3627
 rcu_tasks_wait_gp+0x4a3/0xac0 kernel/rcu/tasks.h:791
 rcu_tasks_one_gp+0xc2b/0xdf0 kernel/rcu/tasks.h:615
 rcu_tasks_kthread+0x19c/0x1c0 kernel/rcu/tasks.h:651
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
INFO: task kworker/u4:134:6149 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:134  state:D stack:24488 pid:6149  ppid:2      flags:0x00004000
Workqueue: ipv6_addrconf addrconf_verify_work
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6834
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0x673/0xc80 kernel/locking/mutex.c:747
 addrconf_verify_work+0x19/0x30 net/ipv6/addrconf.c:4730
 process_one_work kernel/workqueue.c:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
INFO: task syz.5.768:10143 blocked for more than 144 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.5.768       state:D stack:22920 pid:10143 ppid:6451   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 exp_funnel_lock kernel/rcu/tree_exp.h:315 [inline]
 synchronize_rcu_expedited+0x79f/0x880 kernel/rcu/tree_exp.h:1004
 namespace_unlock+0x243/0x440 fs/namespace.c:1581
 drop_collected_mounts fs/namespace.c:2083 [inline]
 put_mnt_ns+0xdf/0x130 fs/namespace.c:4807
 free_nsproxy+0x4d/0x3c0 kernel/nsproxy.c:193
 do_exit+0x981/0x2530 kernel/exit.c:889
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1032
 get_signal+0x12a6/0x1390 kernel/signal.c:2911
 arch_do_signal_or_restart+0xc2/0x7b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 irqentry_exit_to_user_mode+0x9/0x30 kernel/entry/common.c:315
 exc_page_fault+0x8c/0x100 arch/x86/mm/fault.c:1519
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0033:0x3a3f97049a2d
RSP: 002b:0000200000000288 EFLAGS: 00010217
RAX: 0000000000000000 RBX: 00007fb4d0425fa0 RCX: 00007fb4d019e159
RDX: 0000200000000340 RSI: 0000200000000280 RDI: 0000000001020000
RBP: 00007fb4d0235024 R08: 00002000000003c0 R09: 00002000000003c0
R10: 0000200000000380 R11: 0000000000000206 R12: 0000000000000000
R13: 00007fb4d0426038 R14: 00007fb4d0425fa0 R15: 00007ffea8a47508
 </TASK>
INFO: task syz.5.774:10149 blocked for more than 146 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.5.774       state:D stack:25384 pid:10149 ppid:6451   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6834
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0x673/0xc80 kernel/locking/mutex.c:747
 perf_event_detach_bpf_prog+0x8b/0x310 kernel/trace/bpf_trace.c:2215
 perf_event_free_bpf_prog kernel/events/core.c:10735 [inline]
 _free_event+0xb84/0xfb0 kernel/events/core.c:5276
 put_event kernel/events/core.c:5378 [inline]
 perf_event_release_kernel+0x7c8/0x850 kernel/events/core.c:5503
 perf_release+0x3b/0x40 kernel/events/core.c:5513
 __fput+0x221/0x940 fs/file_table.c:418
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb4d019e159
RSP: 002b:00007ffea8a47668 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fb4d0427da0 RCX: 00007fb4d019e159
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007fb4d0427da0 R08: 0000000000000006 R09: 0000000000000000
R10: 00007fb4d0427cb0 R11: 0000000000000246 R12: 0000000000044928
R13: 00007fb4d042645c R14: 0000000000044705 R15: 00007ffea8a47770
 </TASK>
INFO: task syz.5.774:10164 blocked for more than 147 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.5.774       state:D stack:25832 pid:10164 ppid:6451   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 synchronize_rcu_expedited+0x6d8/0x880 kernel/rcu/tree_exp.h:1019
 synchronize_rcu+0x142/0x3e0 kernel/rcu/tree.c:3627
 bpf_dispatcher_update kernel/bpf/dispatcher.c:131 [inline]
 bpf_dispatcher_change_prog+0xd61/0xf10 kernel/bpf/dispatcher.c:170
 bpf_prog_test_run_xdp+0x74f/0x1140 net/bpf/test_run.c:1323
 bpf_prog_test_run+0x31f/0x390 kernel/bpf/syscall.c:4132
 __sys_bpf+0x49d/0x890 kernel/bpf/syscall.c:5496
 __do_sys_bpf kernel/bpf/syscall.c:5582 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5580 [inline]
 __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5580
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb4d019e159
RSP: 002b:00007fb4d106b028 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007fb4d0426450 RCX: 00007fb4d019e159
RDX: 0000000000000050 RSI: 0000200000002200 RDI: 000000000000000a
RBP: 00007fb4d0235024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb4d04264e8 R14: 00007fb4d0426450 R15: 00007ffea8a47508
 </TASK>
INFO: task syz.4.775:10158 blocked for more than 149 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.775       state:D stack:27048 pid:10158 ppid:6452   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 exp_funnel_lock kernel/rcu/tree_exp.h:315 [inline]
 synchronize_rcu_expedited+0x79f/0x880 kernel/rcu/tree_exp.h:1004
 dev_deactivate_many+0x61e/0xcd0 net/sched/sch_generic.c:1348
 __dev_close_many+0x166/0x2b0 net/core/dev.c:1590
 dev_close_many+0x220/0x410 net/core/dev.c:1628
 unregister_netdevice_many_notify+0x4bf/0x1910 net/core/dev.c:11135
 unregister_netdevice_many net/core/dev.c:11218 [inline]
 unregister_netdevice_queue+0x2e9/0x330 net/core/dev.c:11098
 unregister_netdevice include/linux/netdevice.h:3181 [inline]
 ppp_release+0xf0/0x1f0 drivers/net/ppp/ppp_generic.c:408
 __fput+0x221/0x940 fs/file_table.c:418
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fcedad9e159
RSP: 002b:00007ffd65c76868 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fcedb027da0 RCX: 00007fcedad9e159
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007fcedb027da0 R08: 0000000000000006 R09: 0000000000000000
R10: 00007fcedb027cb0 R11: 0000000000000246 R12: 000000000004499f
R13: 00007fcedb025fac R14: 0000000000044705 R15: 00007ffd65c76970
 </TASK>
INFO: task syz.6.776:10160 blocked for more than 151 seconds.

Crashes (14):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/06 14:58 linux-6.6.y 8b73de7da85f 4f7b22a0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: task hung in synchronize_rcu
2026/09/02 22:41 linux-6.6.y 8b73de7da85f 85995287 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in synchronize_rcu
2026/08/20 04:51 linux-6.6.y c610b395b0a5 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: task hung in synchronize_rcu
2026/08/06 22:42 linux-6.6.y 80dfb0405055 c38879ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in synchronize_rcu
2026/07/31 20:47 linux-6.6.y a1153c0deb44 7664cf44 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in synchronize_rcu
2026/07/26 10:55 linux-6.6.y c5596480c50e 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in synchronize_rcu
2026/06/28 15:03 linux-6.6.y d1cfde2d5d15 fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: task hung in synchronize_rcu
2026/06/25 17:40 linux-6.6.y d1cfde2d5d15 cfa969bf .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: task hung in synchronize_rcu
2026/04/26 13:45 linux-6.6.y 9760bf04666d 9c2d0995 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: task hung in synchronize_rcu
2026/04/20 05:23 linux-6.6.y 9760bf04666d 303e2802 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: task hung in synchronize_rcu
2026/01/15 21:39 linux-6.6.y c596736dadab d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: task hung in synchronize_rcu
2025/12/22 06:24 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: task hung in synchronize_rcu
2025/12/10 21:00 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: task hung in synchronize_rcu
2025/10/30 17:16 linux-6.6.y e5bbb12db2c7 2c50b6a9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in synchronize_rcu
* Struck through repros no longer work on HEAD.