syzbot
INFO: rcu detected stall in sys_truncate (2)
Status: auto-obsoleted due to no activity on 2026/08/28 13:10
Subsystems:
fs
Labels:
prio:high
[Documentation on labels]
First crash: 100d, last: 100d
Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 0-...!: (1 GPs behind) idle=533c/1/0x4000000000000000 softirq=78639/78639 fqs=5
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P5623/1:b..l
rcu: (detected by 1, t=10505 jiffies, g=131773, q=409 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 17516 Comm: syz.1.3864 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:enqueue_hrtimer+0x1e2/0x2f0 kernel/time/hrtimer.c:1120
Code: 00 45 84 e4 74 4b e8 1d 48 14 00 48 8d 7d 28 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 e7 00 00 00 <48> 8d 7b 48 48 8b 6d 28 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48
RSP: 0018:ffffc90000007e58 EFLAGS: 00000046
RAX: dffffc0000000000 RBX: ffff8880b8428600 RCX: ffffffff81f45839
RDX: 1ffff1100a42ae65 RSI: ffffffff81f45843 RDI: ffff888052157328
RBP: ffff888052157300 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000080010001
R13: 0000000000000002 R14: ffff8880b8428608 R15: ffff8880b8428650
FS: 00007f35934be6c0(0000) GS:ffff888124383000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b33e06ff8 CR3: 000000003d2a1000 CR4: 00000000003526f0
Call Trace:
<IRQ>
__run_hrtimer kernel/time/hrtimer.c:1946 [inline]
__hrtimer_run_queues+0x73d/0xa00 kernel/time/hrtimer.c:1994
hrtimer_interrupt+0x3e5/0x940 kernel/time/hrtimer.c:2113
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
__sysvec_apic_timer_interrupt+0x10b/0x460 arch/x86/kernel/apic/apic.c:1067
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline]
sysvec_apic_timer_interrupt+0x9e/0xc0 arch/x86/kernel/apic/apic.c:1061
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:lock_release+0x19e/0x310 kernel/locking/lockdep.c:5893
Code: ff 65 0f c1 05 db 95 25 12 83 f8 01 0f 85 28 01 00 00 9c 58 f6 c4 02 0f 85 13 01 00 00 41 f7 c6 00 02 00 00 0f 85 c0 00 00 00 <48> 8b 44 24 10 65 48 2b 05 2d 4e 25 12 0f 85 4e 01 00 00 48 83 c4
RSP: 0018:ffffc900064e7bf0 EFLAGS: 00000206
RAX: 0000000000000046 RBX: ffffffff8ea6fff0 RCX: ffffc900064e7bfc
RDX: 0000000000000001 RSI: ffffffff8dee9778 RDI: ffffffff8c1c4400
RBP: ffffffff8287ce6c R08: 0000000000000001 R09: ffffed1006ba7b08
R10: ffff888035d3d843 R11: 0000000000000000 R12: ffff888084030000
R13: ffffed1006e0b742 R14: 0000000000000287 R15: 0000000000000002
percpu_up_read include/linux/percpu-rwsem.h:112 [inline]
__break_lease+0xb91/0x19f0 fs/locks.c:1696
break_lease include/linux/filelock.h:485 [inline]
break_lease include/linux/filelock.h:470 [inline]
vfs_truncate+0x5dc/0x720 fs/open.c:112
ksys_truncate+0xee/0x190 fs/open.c:142
__do_sys_truncate fs/open.c:154 [inline]
__se_sys_truncate fs/open.c:152 [inline]
__x64_sys_truncate+0x54/0x80 fs/open.c:152
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f359259ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f35934be028 EFLAGS: 00000246 ORIG_RAX: 000000000000004c
RAX: ffffffffffffffda RBX: 00007f3592815fa0 RCX: 00007f359259ce59
RDX: 0000000000000000 RSI: 0000000000002000 RDI: 00002000000006c0
RBP: 00007f3592632d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3592816038 R14: 00007f3592815fa0 R15: 00007ffd20cb80d8
</TASK>
task:syz-executor state:R running task stack:22952 pid:5623 tgid:5623 ppid:5610 task_flags:0x400140 flags:0x00080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5388 [inline]
__schedule+0x1295/0x67a0 kernel/sched/core.c:7189
preempt_schedule_common+0x42/0xc0 kernel/sched/core.c:7370
preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
__raw_spin_unlock include/linux/spinlock_api_smp.h:169 [inline]
_raw_spin_unlock+0x3e/0x50 kernel/locking/spinlock.c:190
spin_unlock include/linux/spinlock.h:390 [inline]
copy_pte_range mm/memory.c:1347 [inline]
copy_pmd_range mm/memory.c:1408 [inline]
copy_pud_range mm/memory.c:1445 [inline]
copy_p4d_range mm/memory.c:1469 [inline]
copy_page_range+0x1c1f/0x5b20 mm/memory.c:1555
dup_mmap+0xd44/0x21b0 mm/mmap.c:1840
dup_mm kernel/fork.c:1534 [inline]
copy_mm kernel/fork.c:1586 [inline]
copy_process+0x6c78/0x7ed0 kernel/fork.c:2264
kernel_clone+0x176/0x9e0 kernel/fork.c:2722
__do_sys_clone+0xd9/0x120 kernel/fork.c:2863
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1ff9bc58d2
RSP: 002b:00007fff16c22400 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007fff16c22400 RCX: 00007f1ff9bc58d2
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007fff16c2258c R08: 0000000000000000 R09: 0000000000000001
R10: 000055557bc397d0 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000000927c0 R14: 00000000000d4fce R15: 00007fff16c225e0
</TASK>
rcu: rcu_preempt kthread starved for 10480 jiffies! g131773 f0x0 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:28904 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5388 [inline]
__schedule+0x1295/0x67a0 kernel/sched/core.c:7189
__schedule_loop kernel/sched/core.c:7268 [inline]
schedule+0xdd/0x390 kernel/sched/core.c:7283
schedule_timeout+0x127/0x280 kernel/time/sleep_timeout.c:99
rcu_gp_fqs_loop+0x1a9/0x900 kernel/rcu/tree.c:2095
rcu_gp_kthread+0x179/0x230 kernel/rcu/tree.c:2297
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:
CPU: 1 UID: 0 PID: 17525 Comm: syz.4.3868 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:csd_lock_wait kernel/smp.c:342 [inline]
RIP: 0010:smp_call_function_many_cond+0x589/0x1700 kernel/smp.c:892
Code: b8 00 00 00 00 00 fc ff df 48 8b 54 24 08 49 89 d5 49 89 d4 49 c1 ed 03 41 83 e4 07 49 01 c5 41 83 c4 03 e8 39 84 0c 00 f3 90 <41> 0f b6 45 00 41 38 c4 7c 08 84 c0 0f 85 63 0f 00 00 8b 45 08 31
RSP: 0018:ffffc900065178a8 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81fc1c4d
RDX: ffff88808343ca80 RSI: ffffffff81fc1c27 RDI: ffff88808343ca80
RBP: ffff8880b8443360 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000003
R13: ffffed101708866d R14: 0000000000000001 R15: ffff8880b853c600
FS: 0000000000000000(0000) GS:ffff888124483000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffcee5eed10 CR3: 00000000775d6000 CR4: 00000000003526f0
Call Trace:
<TASK>
on_each_cpu_cond_mask+0x40/0x90 kernel/smp.c:1057
__flush_tlb_multi arch/x86/include/asm/paravirt.h:46 [inline]
flush_tlb_multi arch/x86/mm/tlb.c:1361 [inline]
flush_tlb_mm_range+0x45f/0x16f0 arch/x86/mm/tlb.c:1451
tlb_flush arch/x86/include/asm/tlb.h:23 [inline]
tlb_flush_mmu_tlbonly include/asm-generic/tlb.h:509 [inline]
tlb_flush_mmu_tlbonly include/asm-generic/tlb.h:499 [inline]
tlb_flush_mmu mm/mmu_gather.c:423 [inline]
tlb_finish_mmu+0x3fe/0x810 mm/mmu_gather.c:549
exit_mmap+0x454/0xa10 mm/mmap.c:1313
__mmput+0x12a/0x410 kernel/fork.c:1178
mmput+0x67/0x80 kernel/fork.c:1201
exit_mm kernel/exit.c:582 [inline]
do_exit+0x8b2/0x2af0 kernel/exit.c:964
do_group_exit+0xd5/0x2a0 kernel/exit.c:1119
__do_sys_exit_group kernel/exit.c:1130 [inline]
__se_sys_exit_group kernel/exit.c:1128 [inline]
__x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1128
x64_sys_call+0x102c/0x1530 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa80139ce59
Code: Unable to access opcode bytes at 0x7fa80139ce2f.
RSP: 002b:00007ffff2ba2ea8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fa80139ce59
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007ffff2ba2f0c R08: 0000000000000000 R09: 00000000000927c0
R10: 00007fa801616128 R11: 0000000000000246 R12: 0000000000000307
R13: 00000000000927c0 R14: 00000000000d4d0b R15: 00007ffff2ba2f60
</TASK>
Struck through repros no longer work on HEAD.