BUG: soft lockup in __hrtimer_run_queues

Status: upstream: reported on 2026/10/02 17:39
Reported-by: syzbot+b8bc2ae8a4388e1a6b84@syzkaller.appspotmail.com
First crash: 20h16m, last: 20h16m
▶ ▼ Similar bugs (8)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream BUG: soft lockup in __hrtimer_run_queues (4) kernel 1 1 549d 545d 0/29 auto-obsoleted due to no activity on 2025/06/30 23:58
upstream INFO: rcu detected stall in __hrtimer_run_queues (3) prio:high kernel 1 syz, C 51 3d18h 55d 0/29 upstream: reported C repro on 2026/08/08 20:09
upstream BUG: soft lockup in __hrtimer_run_queues (2) kernel 1 1 825d 821d 0/29 auto-obsoleted due to no activity on 2024/09/27 22:42
upstream BUG: soft lockup in __hrtimer_run_queues (3) kernel 1 1 642d 638d 0/29 auto-obsoleted due to no activity on 2025/03/30 03:09
upstream BUG: soft lockup in __hrtimer_run_queues kernel 1 2 2087d 2131d 0/29 auto-closed as invalid on 2021/04/15 12:33
upstream INFO: rcu detected stall in __hrtimer_run_queues kernel 1 syz, C inconclusive done 22 1504d 2050d 0/29 auto-obsoleted due to no activity on 2022/12/19 03:45
linux-5.15 INFO: rcu detected stall in __hrtimer_run_queues 1 1 57d 57d 0/3 upstream: reported on 2026/08/07 07:45
upstream INFO: rcu detected stall in __hrtimer_run_queues (2) kernel 1 1 458d 458d 0/29 auto-obsoleted due to no activity on 2025/09/29 21:02

Sample crash report:
watchdog: BUG: soft lockup - CPU#0 stuck for 26s! [ksoftirqd/0:15]
Modules linked in:
irq event stamp: 58403685
hardirqs last  enabled at (58403684): [<ffff800011c9da4c>] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline]
hardirqs last  enabled at (58403684): [<ffff800011c9da4c>] _raw_spin_unlock_irqrestore+0x48/0xac kernel/locking/spinlock.c:194
hardirqs last disabled at (58403685): [<ffff800011bb2924>] __el1_irq arch/arm64/kernel/entry-common.c:468 [inline]
hardirqs last disabled at (58403685): [<ffff800011bb2924>] el1_interrupt+0x24/0x54 arch/arm64/kernel/entry-common.c:486
softirqs last  enabled at (1960992): [<ffff8000081ae3b4>] softirq_handle_end kernel/softirq.c:439 [inline]
softirqs last  enabled at (1960992): [<ffff8000081ae3b4>] handle_softirqs+0xb1c/0xc90 kernel/softirq.c:624
softirqs last disabled at (1960997): [<ffff8000081b1364>] run_ksoftirqd+0x7c/0x2ac kernel/softirq.c:968
CPU: 0 PID: 15 Comm: ksoftirqd/0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2026
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
pc : _raw_spin_unlock_irqrestore+0x58/0xac kernel/locking/spinlock.c:194
lr : __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline]
lr : _raw_spin_unlock_irqrestore+0x48/0xac kernel/locking/spinlock.c:194
sp : ffff80001cbd7ac0
x29: ffff80001cbd7ac0 x28: ffff0000f50b9d48 x27: ffff00019f34fc00
x26: ffff00019f34f944 x25: 0000000000000005 x24: ffff00019f34fc10
x23: 0000000000000001 x22: 1fffe00033e69f82 x21: 1fffe0001ea173b0
x20: ffff00019f34f900 x19: 0000000000000000 x18: 1fffe00033e6997e
x17: ffff8000081adbb0 x16: ffff8000082dd284 x15: 0000000000000000
x14: 0000000000000001 x13: 1fffe00033e69f20 x12: 0000000000000000
x11: ff0080000a97ca20 x10: 0000000000000003 x9 : 0000000000000080
x8 : 00000000000000c0 x7 : ffff80000a97dfc4 x6 : 0000000000000000
x5 : 0000000000000080 x4 : 0000000000000001 x3 : 0000000000000000
x2 : ffff80001cbd7a00 x1 : ffff800011d1dc80 x0 : ffff80018a036000
Call trace:
 arch_local_irq_restore arch/arm64/include/asm/irqflags.h:122 [inline]
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline]
 _raw_spin_unlock_irqrestore+0x58/0xac kernel/locking/spinlock.c:194
 __run_hrtimer kernel/time/hrtimer.c:1747 [inline]
 __hrtimer_run_queues+0x334/0xc58 kernel/time/hrtimer.c:1815
 hrtimer_run_softirq+0x164/0x408 kernel/time/hrtimer.c:1832
 handle_softirqs+0x318/0xc90 kernel/softirq.c:596
 run_ksoftirqd+0x7c/0x2ac kernel/softirq.c:968
 smpboot_thread_fn+0x4e8/0x960 kernel/smpboot.c:164
 kthread+0x254/0x2e0 kernel/kthread.c:376
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/02 17:38 linux-6.1.y 1a8763b93150 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 BUG: soft lockup in __hrtimer_run_queues
* Struck through repros no longer work on HEAD.