INFO: task syz-executor:29013 blocked for more than 143 seconds.
Not tainted 6.13.0-rc2-syzkaller-00362-g2d8308bf5b67 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor state:D stack:21280 pid:29013 tgid:29013 ppid:1 flags:0x00000004
Call Trace:
context_switch kernel/sched/core.c:5369 [inline]
__schedule+0x1850/0x4c30 kernel/sched/core.c:6756
__schedule_loop kernel/sched/core.c:6833 [inline]
schedule+0x14b/0x320 kernel/sched/core.c:6848
schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6905
__mutex_lock_common kernel/locking/mutex.c:665 [inline]
__mutex_lock+0x7e7/0xee0 kernel/locking/mutex.c:735
del_device_store+0xfc/0x480 drivers/net/netdevsim/bus.c:216
kernfs_fop_write_iter+0x3a0/0x500 fs/kernfs/file.c:334
new_sync_write fs/read_write.c:586 [inline]
vfs_write+0xaeb/0xd30 fs/read_write.c:679
ksys_write+0x18f/0x2b0 fs/read_write.c:731
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7294d847cf
RSP: 002b:00007f729509f220 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00007f7294d847cf
RDX: 0000000000000001 RSI: 00007f729509f270 RDI: 0000000000000005
RBP: 00007f7294e02c2d R08: 0000000000000000 R09: 00007f729509f077
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001
R13: 00007f729509f270 R14: 00007f7295aa4620 R15: 0000000000000003
Showing all locks held in the system:
4 locks held by ksoftirqd/0/16:
1 lock held by khungtaskd/30:
#0: ffffffff8e937ae0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
#0: ffffffff8e937ae0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
#0: ffffffff8e937ae0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x55/0x2a0 kernel/locking/lockdep.c:6744
4 locks held by kworker/u8:8/3460:
#0: ffff88801baed948 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3204 [inline]
#0: ffff88801baed948 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1840 kernel/workqueue.c:3310
#1: ffffc9000ccf7d00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3205 [inline]
#1: ffffc9000ccf7d00 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1840 kernel/workqueue.c:3310
#2: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0x16a/0xd50 net/core/net_namespace.c:602
#3: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: ipmr_net_exit_batch+0x20/0x90 net/ipv4/ipmr.c:3158
1 lock held by dhcpcd/5500:
#0: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:79 [inline]
#0: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:326 [inline]
#0: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0xbcb/0x2150 net/core/rtnetlink.c:4010
2 locks held by getty/5583:
#0: ffff888030a240a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc9000332b2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x6a6/0x1e00 drivers/tty/n_tty.c:2211
3 locks held by kworker/1:4/5881:
#0: ffff88801ac80948 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3204 [inline]
#0: ffff88801ac80948 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1840 kernel/workqueue.c:3310
#1: ffffc9000414fd00 (deferred_process_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3205 [inline]
#1: ffffc9000414fd00 (deferred_process_work){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1840 kernel/workqueue.c:3310
#2: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: switchdev_deferred_process_work+0xe/0x20 net/switchdev/switchdev.c:104
3 locks held by kworker/u8:15/10610:
#0: ffff8880303f4948 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3204 [inline]
#0: ffff8880303f4948 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1840 kernel/workqueue.c:3310
#1: ffffc90003507d00 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3205 [inline]
#1: ffffc90003507d00 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1840 kernel/workqueue.c:3310
#2: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_dad_work+0xd0/0x16f0 net/ipv6/addrconf.c:4215
2 locks held by kworker/u8:9/27028:
3 locks held by kworker/u8:11/27029:
#0: ffff88801ac89148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3204 [inline]
#0: ffff88801ac89148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1840 kernel/workqueue.c:3310
#1: ffffc9000489fd00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3205 [inline]
#1: ffffc9000489fd00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1840 kernel/workqueue.c:3310
#2: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: linkwatch_event+0xe/0x60 net/core/link_watch.c:281
2 locks held by syz.1.3312/28875:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: ip_tunnel_init_net+0x20e/0x720 net/ipv4/ip_tunnel.c:1159
2 locks held by syz-executor/28933:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: ppp_exit_net+0xe3/0x3d0 drivers/net/ppp/ppp_generic.c:1146
8 locks held by syz-executor/28946:
#0: ffff888034fb0420 (sb_writers#8){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2964 [inline]
#0: ffff888034fb0420 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x225/0xd30 fs/read_write.c:675
#1: ffff8880699b3c88 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1ea/0x500 fs/kernfs/file.c:325
#2: ffff888027c27788 (kn->active#49){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x20e/0x500 fs/kernfs/file.c:326
#3: ffffffff8f55e628 (nsim_bus_dev_list_lock){+.+.}-{4:4}, at: del_device_store+0xfc/0x480 drivers/net/netdevsim/bus.c:216
#4: ffff88805bc530e8 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:1014 [inline]
#4: ffff88805bc530e8 (&dev->mutex){....}-{4:4}, at: __device_driver_lock drivers/base/dd.c:1095 [inline]
#4: ffff88805bc530e8 (&dev->mutex){....}-{4:4}, at: device_release_driver_internal+0xce/0x7c0 drivers/base/dd.c:1293
#5: ffff888077366250 (&devlink->lock_key#67){+.+.}-{4:4}, at: nsim_drv_remove+0x50/0x160 drivers/net/netdevsim/dev.c:1675
#6: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: nsim_destroy+0x71/0x5c0 drivers/net/netdevsim/netdev.c:816
#7: ffffffff8e7d2ed0 (cpu_hotplug_lock){++++}-{0:0}, at: flush_all_backlogs net/core/dev.c:6031 [inline]
#7: ffffffff8e7d2ed0 (cpu_hotplug_lock){++++}-{0:0}, at: unregister_netdevice_many_notify+0x5ea/0x1da0 net/core/dev.c:11507
2 locks held by syz-executor/28986:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: ip_tunnel_init_net+0x20e/0x720 net/ipv4/ip_tunnel.c:1159
2 locks held by syz-executor/28992:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: wg_netns_pre_exit+0x1f/0x1e0 drivers/net/wireguard/device.c:415
2 locks held by syz-executor/29000:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: ip_tunnel_init_net+0x20e/0x720 net/ipv4/ip_tunnel.c:1159
2 locks held by syz-executor/29002:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: ip_tunnel_init_net+0x20e/0x720 net/ipv4/ip_tunnel.c:1159
2 locks held by syz-executor/29007:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: caif_exit_net+0x6f/0x4a0 net/caif/caif_dev.c:528
4 locks held by syz-executor/29013:
#0: ffff888034fb0420 (sb_writers#8){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2964 [inline]
#0: ffff888034fb0420 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x225/0xd30 fs/read_write.c:675
#1: ffff888037b99c88 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1ea/0x500 fs/kernfs/file.c:325
#2: ffff888027c27788 (kn->active#49){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x20e/0x500 fs/kernfs/file.c:326
#3: ffffffff8f55e628 (nsim_bus_dev_list_lock){+.+.}-{4:4}, at: del_device_store+0xfc/0x480 drivers/net/netdevsim/bus.c:216
2 locks held by syz-executor/29026:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: ip_tunnel_init_net+0x20e/0x720 net/ipv4/ip_tunnel.c:1159
2 locks held by syz-executor/29038:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: ip_tunnel_init_net+0x20e/0x720 net/ipv4/ip_tunnel.c:1159
2 locks held by syz-executor/29039:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: ip_tunnel_init_net+0x20e/0x720 net/ipv4/ip_tunnel.c:1159
2 locks held by syz-executor/29044:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: ip_tunnel_init_net+0x20e/0x720 net/ipv4/ip_tunnel.c:1159
2 locks held by syz-executor/29051:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: ip_tunnel_init_net+0x20e/0x720 net/ipv4/ip_tunnel.c:1159
2 locks held by syz-executor/29058:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: register_nexthop_notifier+0x84/0x290 net/ipv4/nexthop.c:3878
2 locks held by syz-executor/29070:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: register_nexthop_notifier+0x84/0x290 net/ipv4/nexthop.c:3878
2 locks held by syz-executor/29071:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: register_nexthop_notifier+0x84/0x290 net/ipv4/nexthop.c:3878
2 locks held by syz-executor/29077:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: register_nexthop_notifier+0x84/0x290 net/ipv4/nexthop.c:3878
2 locks held by syz-executor/29084:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: register_nexthop_notifier+0x84/0x290 net/ipv4/nexthop.c:3878
2 locks held by syz-executor/29091:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: register_nexthop_notifier+0x84/0x290 net/ipv4/nexthop.c:3878
2 locks held by syz-executor/29099:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: register_nexthop_notifier+0x84/0x290 net/ipv4/nexthop.c:3878
2 locks held by syz-executor/29101:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: register_nexthop_notifier+0x84/0x290 net/ipv4/nexthop.c:3878
2 locks held by syz-executor/29104:
#0: ffffffff8fca6390 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x328/0x570 net/core/net_namespace.c:512
#1: ffffffff8fcb2848 (rtnl_mutex){+.+.}-{4:4}, at: register_nexthop_notifier+0x84/0x290 net/ipv4/nexthop.c:3878
=============================================
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 30 Comm: khungtaskd Not tainted 6.13.0-rc2-syzkaller-00362-g2d8308bf5b67 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024
Call Trace:
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
nmi_cpu_backtrace+0x49c/0x4d0 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x198/0x320 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:234 [inline]
watchdog+0xff6/0x1040 kernel/hung_task.c:397
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 1205 Comm: kworker/0:2 Not tainted 6.13.0-rc2-syzkaller-00362-g2d8308bf5b67 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024
Workqueue: wg-kex-wg2 wg_packet_handshake_receive_worker
RIP: 0010:kernel_text_address+0x5/0xe0 kernel/extable.c:95
Code: c2 20 ca 08 c2 0f b6 c2 5b c3 cc cc 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 66 0f 1f 00 55 <41> 56 53 48 89 fb 48 c7 c0 00 00 00 81 bd 01 00 00 00 48 39 c7 72
RSP: 0018:ffffc90000006b60 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffffffff86779dc2 RCX: 0000000080000101
RDX: dffffc0000000000 RSI: ffffc90004558000 RDI: ffffffff86779dc2
RBP: ffffc90000006c30 R08: ffffc9000455f970 R09: 0000000000000000
R10: ffffc90000006bf0 R11: fffff52000000d80 R12: ffff8880277d5a00
R13: ffffffff818b2450 R14: dffffc0000000000 R15: 1ffff92000000d7d
FS: 0000000000000000(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c3e5cb8 CR3: 000000000e736000 CR4: 00000000003526f0
Call Trace:
__kernel_text_address+0xd/0x40 kernel/extable.c:79
unwind_get_return_address+0x4d/0x90 arch/x86/kernel/unwind_orc.c:369
arch_stack_walk+0xfd/0x150 arch/x86/kernel/stacktrace.c:26
stack_trace_save+0x118/0x1d0 kernel/stacktrace.c:122
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
unpoison_slab_object mm/kasan/common.c:319 [inline]
__kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:345
kasan_slab_alloc include/linux/kasan.h:250 [inline]
slab_post_alloc_hook mm/slub.c:4119 [inline]
slab_alloc_node mm/slub.c:4168 [inline]
kmem_cache_alloc_noprof+0x1d9/0x380 mm/slub.c:4175
skb_clone+0x20c/0x390 net/core/skbuff.c:2084
deliver_clone net/bridge/br_forward.c:125 [inline]
br_flood+0x3dc/0x660 net/bridge/br_forward.c:245
br_handle_frame_finish+0x18ba/0x1fe0 net/bridge/br_input.c:215
br_nf_hook_thresh+0x472/0x590
br_nf_pre_routing_finish_ipv6+0xaa0/0xdd0
NF_HOOK include/linux/netfilter.h:314 [inline]
br_nf_pre_routing_ipv6+0x379/0x770 net/bridge/br_netfilter_ipv6.c:184
nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline]
nf_hook_bridge_pre net/bridge/br_input.c:277 [inline]
br_handle_frame+0x9fd/0x1530 net/bridge/br_input.c:424
__netif_receive_skb_core+0x14eb/0x4690 net/core/dev.c:5566
__netif_receive_skb_one_core net/core/dev.c:5670 [inline]
__netif_receive_skb+0x12f/0x650 net/core/dev.c:5785
process_backlog+0x662/0x15b0 net/core/dev.c:6117
__napi_poll+0xcb/0x490 net/core/dev.c:6883
napi_poll net/core/dev.c:6952 [inline]
net_rx_action+0x89b/0x1240 net/core/dev.c:7074
handle_softirqs+0x2d4/0x9b0 kernel/softirq.c:561
do_softirq+0x11b/0x1e0 kernel/softirq.c:462
__local_bh_enable_ip+0x1bb/0x200 kernel/softirq.c:389
local_bh_enable include/linux/bottom_half.h:33 [inline]
rcu_read_unlock_bh include/linux/rcupdate.h:919 [inline]
wg_noise_handshake_begin_session+0x846/0xb80 drivers/net/wireguard/noise.c:856
wg_receive_handshake_packet drivers/net/wireguard/receive.c:176 [inline]
wg_packet_handshake_receive_worker+0x632/0xf50 drivers/net/wireguard/receive.c:213
process_one_work kernel/workqueue.c:3229 [inline]
process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310
worker_thread+0x870/0xd30 kernel/workqueue.c:3391
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
vkms_vblank_simulate: vblank timer overrun