syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P9746/1:b..l
	(detected by 1, t=10503 jiffies, g=46045, q=21 ncpus=2)
task:syz.2.1719      state:R  running task     stack:25232 pid:9746  ppid:4268   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5245 [inline]
 __schedule+0x11d1/0x40e0 kernel/sched/core.c:6562
 preempt_schedule_notrace+0xd9/0x120 kernel/sched/core.c:6824
 preempt_schedule_notrace_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:35
 rcu_is_watching+0x76/0xa0 kernel/rcu/tree.c:722
 rcu_read_unlock include/linux/rcupdate.h:820 [inline]
 mapping_get_entry mm/filemap.c:1899 [inline]
 __filemap_get_folio+0x340/0xdb0 mm/filemap.c:1943
 shmem_get_folio_gfp+0x310/0x3400 mm/shmem.c:1881
 shmem_fault+0x1b6/0x780 mm/shmem.c:2156
 __do_fault+0x13b/0x4e0 mm/memory.c:4278
 do_read_fault mm/memory.c:4629 [inline]
 do_fault mm/memory.c:4758 [inline]
 handle_pte_fault mm/memory.c:5029 [inline]
 __handle_mm_fault mm/memory.c:5171 [inline]
 handle_mm_fault+0x2407/0x3ee0 mm/memory.c:5292
 faultin_page mm/gup.c:1026 [inline]
 __get_user_pages+0x40d/0xec0 mm/gup.c:1250
 populate_vma_page_range+0x214/0x2b0 mm/gup.c:1607
 __mm_populate+0x25c/0x380 mm/gup.c:1721
 mm_populate include/linux/mm.h:2891 [inline]
 vm_mmap_pgoff+0x212/0x2d0 mm/util.c:525
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7ff01f39bf79
RSP: 002b:00007ff02022d028 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007ff01f615fa0 RCX: 00007ff01f39bf79
RDX: 0000000002000004 RSI: 0000000000b36000 RDI: 0000200000000000
RBP: 00007ff01f4327e0 R08: ffffffffffffffff R09: 0000000055c4c000
R10: 0000000000008031 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff01f616038 R14: 00007ff01f615fa0 R15: 00007ffd096a1ce8
 </TASK>
rcu: rcu_preempt kthread starved for 10520 jiffies! g46045 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
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:28016 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5245 [inline]
 __schedule+0x11d1/0x40e0 kernel/sched/core.c:6562
 schedule+0xb9/0x180 kernel/sched/core.c:6638
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x303/0x1340 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x99/0x3b0 kernel/rcu/tree.c:1905
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 9762 Comm: syz.5.1724 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:hlock_class kernel/locking/lockdep.c:228 [inline]
RIP: 0010:check_wait_context kernel/locking/lockdep.c:4723 [inline]
RIP: 0010:__lock_acquire+0x549/0x7d10 kernel/locking/lockdep.c:4999
Code: 81 e3 ff 1f 00 00 41 c1 ed 03 41 81 e5 f8 03 00 00 49 8d bd 40 42 af 90 be 08 00 00 00 e8 3f 17 6f 00 48 0f a3 1d 87 f8 4a 0f <73> 1f 48 8d 04 5b c1 e0 06 48 8d 98 00 c1 47 90 48 ba 00 00 00 00
RSP: 0018:ffffc90012287580 EFLAGS: 00000057
RAX: 0000000000000001 RBX: 0000000000000049 RCX: ffffffff816449b1
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff90af4248
RBP: ffffc900122877d0 R08: ffffffff90af424f R09: 1ffffffff215e849
R10: dffffc0000000000 R11: fffffbfff215e84a R12: ffff88802a129dc0
R13: 0000000000000008 R14: 0000000000000000 R15: 0000000000000049
FS:  00007f915871c6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2fa1fff8 CR3: 000000003ac80000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5662
 seqcount_lockdep_reader_access+0xcd/0x1d0 include/linux/seqlock.h:102
 timekeeping_get_delta kernel/time/timekeeping.c:254 [inline]
 timekeeping_get_ns kernel/time/timekeeping.c:388 [inline]
 ktime_get+0x7b/0x270 kernel/time/timekeeping.c:848
 clockevents_program_event+0xe2/0x310 kernel/time/clockevents.c:326
 hrtimer_start_range_ns+0xb9a/0xfc0 kernel/time/hrtimer.c:1349
 posixtimer_rearm+0x131/0x340 kernel/time/posix-timers.c:329
 dequeue_signal+0x1b6/0x4b0 kernel/signal.c:704
 get_signal+0x547/0x1350 kernel/signal.c:2751
 arch_do_signal_or_restart+0xc4/0x1350 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f915779bf77
Code: 83 c8 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
RSP: 002b:00007f915871c0e8 EFLAGS: 00000246
RAX: 00000000000000ca RBX: 00007f9157a15fa8 RCX: 00007f915779bf79
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f9157a15fa8
RBP: 00007f9157a15fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9157a16038 R14: 00007fffc74ca2b0 R15: 00007fffc74ca398
 </TASK>