BUG: soft lockup in gate_timer_func

Status: upstream: reported C repro on 2026/08/17 16:04
Subsystems: kernel
Labels: prio:normal
[Documentation on labels]
Reported-by: syzbot+0054fed3dc9085390f51@syzkaller.appspotmail.com
First crash: 23d, last: 4d11h
✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision
4544dad7 repro-c Reproduced: ✅ BUG: soft lockup in gate_timer_func 2026/08/16 13:30 2026/08/16 13:30 2026/08/16 18:10 746171ee
08a1e7df repro-c Reproduced: ✅ BUG: soft lockup in gate_timer_func 2026/08/16 13:30 2026/08/16 13:30 2026/08/16 15:19 746171ee
fc1838a9 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ BUG: soft lockup in gate_timer_func 2026/08/08 22:05 2026/08/08 22:05 2026/08/08 22:50 5d63f80b
Discussions (2)
Title Replies (including bot) Last reply
[PATCH] net/sched: act_gate: Limit the max value for cycletime 10 (10) 2026/08/27 19:17
[syzbot] [kernel?] BUG: soft lockup in gate_timer_func 5 (11) 2026/08/25 12:10
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in gate_timer_func 1 1 6d07h 6d07h 0/3 upstream: reported on 2026/08/23 13:40
Last patch testing requests (6)
Created Duration User Patch Repo Result
2026/08/25 11:32 21m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci OK job log log
2026/08/23 03:23 19m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci OK job log log
2026/08/18 09:37 46m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci OK job log log
2026/08/18 08:24 16m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci OK job log log
2026/08/18 04:45 57m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci OK job log log
2026/08/17 08:59 2h18m nogikh@google.com git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci report job log log

Sample crash report:
watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [syz-executor:4723]
Modules linked in:
irq event stamp: 33138499
hardirqs last  enabled at (33138498): [<ffff800080557c84>] seqcount_lockdep_reader_access+0x7c/0xf8 include/linux/seqlock.h:75
hardirqs last disabled at (33138499): [<ffff80008690b4b4>] __el1_irq arch/arm64/kernel/entry-common.c:527 [inline]
hardirqs last disabled at (33138499): [<ffff80008690b4b4>] el1_interrupt+0x28/0x60 arch/arm64/kernel/entry-common.c:543
softirqs last  enabled at (363270): [<ffff800084bf467c>] spin_unlock_bh include/linux/spinlock.h:396 [inline]
softirqs last  enabled at (363270): [<ffff800084bf467c>] release_sock+0x150/0x228 net/core/sock.c:3869
softirqs last disabled at (363273): [<ffff8000800204c0>] __do_softirq+0x14/0x20 kernel/softirq.c:656
CPU: 1 UID: 0 PID: 4723 Comm: syz-executor Not tainted syzkaller #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
pstate: 43400005 (nZcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
pc : seqcount_lockdep_reader_access+0xd8/0xf8 include/linux/seqlock.h:76
lr : seqcount_lockdep_reader_access+0xd4/0xf8 include/linux/seqlock.h:75
sp : ffff80008eb77ce0
x29: ffff80008eb77ce0 x28: 1fffe00034bbc63a x27: ffff80008e853110
x26: dfff800000000000 x25: ffff0000c831ac80 x24: 1fffe0001aaa7526
x23: dfff800000000000 x22: ffff0000c831acb0 x21: 0000000000000000
x20: ffff8000805580e8 x19: 00000000000000c0 x18: 00000000ffffffff
x17: ffff80008199aec4 x16: ffff80008199b124 x15: ffff80008199c72c
x14: 000000008030dda8 x13: 0000000000000001 x12: ffff0000d456d7c0
x11: ffff80008a5d5e28 x10: 0000000000000003 x9 : 0000000000000101
x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
x5 : 0000000000000001 x4 : 0000000000000008 x3 : ffff800080557cd4
x2 : 0000000000000080 x1 : ffff0000d456d7c0 x0 : 0000000000000000
Call trace:
 __daif_local_irq_restore arch/arm64/include/asm/irqflags.h:175 [inline] (P)
 arch_local_irq_restore arch/arm64/include/asm/irqflags.h:195 [inline] (P)
 seqcount_lockdep_reader_access+0xd8/0xf8 include/linux/seqlock.h:75 (P)
 ktime_get+0x68/0x218 kernel/time/timekeeping.c:971
 gate_get_time+0x1c/0xa4 net/sched/act_gate.c:23
 gate_timer_func+0x1a8/0x390 net/sched/act_gate.c:101
 __run_hrtimer kernel/time/hrtimer.c:2032 [inline]
 __hrtimer_run_queues+0x314/0xbe0 kernel/time/hrtimer.c:2096
 hrtimer_run_softirq+0x15c/0x21c kernel/time/hrtimer.c:2113
 handle_softirqs+0x2ec/0xd98 kernel/softirq.c:622
 __do_softirq+0x14/0x20 kernel/softirq.c:656
 ____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:78
 call_on_irq_stack+0x30/0x48 arch/arm64/kernel/entry.S:885
 do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:83
 invoke_softirq kernel/softirq.c:503 [inline]
 __irq_exit_rcu+0x1ac/0x428 kernel/softirq.c:735
 irq_exit_rcu+0x14/0x84 kernel/softirq.c:752
 __el1_irq arch/arm64/kernel/entry-common.c:531 [inline]
 el1_interrupt+0x40/0x60 arch/arm64/kernel/entry-common.c:543
 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:548
 el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:586
 __sanitizer_cov_trace_pc+0x58/0x5c kernel/kcov.c:235 (P)
 sock_write_iter+0x220/0x310 net/socket.c:1241
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x51c/0xa0c fs/read_write.c:687
 ksys_write+0x12c/0x228 fs/read_write.c:739
 __do_sys_write fs/read_write.c:750 [inline]
 __se_sys_write fs/read_write.c:747 [inline]
 __arm64_sys_write+0x84/0x98 fs/read_write.c:747
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
 do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
 el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:758
 el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:777
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:590
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at __daif_local_irq_enable arch/arm64/include/asm/irqflags.h:26 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_local_irq_enable arch/arm64/include/asm/irqflags.h:48 [inline]
NMI backtrace for cpu 0 skipped: idling at default_idle_call+0xd0/0xfc kernel/sched/idle.c:129

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/24 04:16 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 21d6ac051080 1e72964b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 BUG: soft lockup in gate_timer_func
2026/08/17 16:03 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 21d6ac051080 cd5b1963 .config console log report C ci-upstream-gce-arm64 BUG: soft lockup in gate_timer_func
2026/08/25 09:41 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 68f892e99df9 614e416a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 BUG: soft lockup in gate_timer_func
2026/08/05 23:09 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 7235a3e71949 cd5b1963 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 BUG: soft lockup in gate_timer_func
* Struck through repros no longer work on HEAD.