syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
rcu_preempt/15 is trying to acquire lock:
ffff8880b903a358 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x26/0x140 kernel/sched/core.c:475

but task is already holding lock:
ffffffff8c120b98 (rcu_node_0){-.-.}-{2:2}, at: force_qs_rnp kernel/rcu/tree.c:2646 [inline]
ffffffff8c120b98 (rcu_node_0){-.-.}-{2:2}, at: rcu_gp_fqs kernel/rcu/tree.c:-1 [inline]
ffffffff8c120b98 (rcu_node_0){-.-.}-{2:2}, at: rcu_gp_fqs_loop+0x768/0x11b0 kernel/rcu/tree.c:1986

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (rcu_node_0){-.-.}-{2:2}:
       __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
       _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
       check_cb_ovld kernel/rcu/tree.c:2974 [inline]
       __call_rcu kernel/rcu/tree.c:3025 [inline]
       call_rcu+0x312/0x930 kernel/rcu/tree.c:3091
       queue_rcu_work+0x81/0x90 kernel/workqueue.c:1788
       kfree_rcu_monitor+0x5fe/0x730 kernel/rcu/tree.c:3418
       process_one_work+0x863/0x1000 kernel/workqueue.c:2310
       worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
       kthread+0x436/0x520 kernel/kthread.c:334
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

-> #2 (krc.lock){..-.}-{2:2}:
       __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
       _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
       krc_this_cpu_lock kernel/rcu/tree.c:3203 [inline]
       add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3510 [inline]
       kvfree_call_rcu+0x186/0x7c0 kernel/rcu/tree.c:3601
       trie_update_elem+0x86e/0xc50 kernel/bpf/lpm_trie.c:396
       bpf_map_update_value+0x57d/0x650 kernel/bpf/syscall.c:223
       generic_map_update_batch+0x525/0x7c0 kernel/bpf/syscall.c:1430
       bpf_map_do_batch+0x466/0x600 kernel/bpf/syscall.c:-1
       __sys_bpf+0x601/0x670 kernel/bpf/syscall.c:-1
       __do_sys_bpf kernel/bpf/syscall.c:4761 [inline]
       __se_sys_bpf kernel/bpf/syscall.c:4759 [inline]
       __x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4759
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #1 (&trie->lock){-.-.}-{2:2}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162
       trie_delete_elem+0x90/0x710 kernel/bpf/lpm_trie.c:467
       0xffffffffa002e230
       bpf_dispatcher_nop_func include/linux/bpf.h:888 [inline]
       __bpf_prog_run include/linux/filter.h:628 [inline]
       bpf_prog_run include/linux/filter.h:635 [inline]
       __bpf_trace_run kernel/trace/bpf_trace.c:1878 [inline]
       bpf_trace_run3+0x17e/0x320 kernel/trace/bpf_trace.c:1916
       __traceiter_sched_switch+0x83/0xb0 include/trace/events/sched.h:220
       trace_sched_switch include/trace/events/sched.h:220 [inline]
       __schedule+0x1d71/0x4390 kernel/sched/core.c:6392
       schedule+0x11b/0x1e0 kernel/sched/core.c:6478
       freezable_schedule include/linux/freezer.h:172 [inline]
       futex_wait_queue_me+0x22d/0x440 kernel/futex/core.c:2863
       futex_wait+0x202/0x5c0 kernel/futex/core.c:2964
       do_futex+0xd1c/0x1240 kernel/futex/core.c:3982
       __do_sys_futex kernel/futex/core.c:4059 [inline]
       __se_sys_futex+0x3a3/0x430 kernel/futex/core.c:4040
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (&rq->__lock){-.-.}-{2:2}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
       lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
       _raw_spin_lock_nested+0x2e/0x40 kernel/locking/spinlock.c:368
       raw_spin_rq_lock_nested+0x26/0x140 kernel/sched/core.c:475
       raw_spin_rq_lock kernel/sched/sched.h:1326 [inline]
       _raw_spin_rq_lock_irqsave kernel/sched/sched.h:1345 [inline]
       resched_cpu+0xd4/0x240 kernel/sched/core.c:994
       rcu_implicit_dynticks_qs+0x438/0xc30 kernel/rcu/tree.c:1329
       force_qs_rnp kernel/rcu/tree.c:2664 [inline]
       rcu_gp_fqs kernel/rcu/tree.c:-1 [inline]
       rcu_gp_fqs_loop+0x972/0x11b0 kernel/rcu/tree.c:1986
       rcu_gp_kthread+0x98/0x350 kernel/rcu/tree.c:2145
       kthread+0x436/0x520 kernel/kthread.c:334
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

other info that might help us debug this:

Chain exists of:
  &rq->__lock --> krc.lock --> rcu_node_0

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(rcu_node_0);
                               lock(krc.lock);
                               lock(rcu_node_0);
  lock(&rq->__lock);

 *** DEADLOCK ***

1 lock held by rcu_preempt/15:
 #0: ffffffff8c120b98 (rcu_node_0){-.-.}-{2:2}, at: force_qs_rnp kernel/rcu/tree.c:2646 [inline]
 #0: ffffffff8c120b98 (rcu_node_0){-.-.}-{2:2}, at: rcu_gp_fqs kernel/rcu/tree.c:-1 [inline]
 #0: ffffffff8c120b98 (rcu_node_0){-.-.}-{2:2}, at: rcu_gp_fqs_loop+0x768/0x11b0 kernel/rcu/tree.c:1986

stack backtrace:
CPU: 1 PID: 15 Comm: rcu_preempt Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 check_noncircular+0x274/0x310 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
 lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
 _raw_spin_lock_nested+0x2e/0x40 kernel/locking/spinlock.c:368
 raw_spin_rq_lock_nested+0x26/0x140 kernel/sched/core.c:475
 raw_spin_rq_lock kernel/sched/sched.h:1326 [inline]
 _raw_spin_rq_lock_irqsave kernel/sched/sched.h:1345 [inline]
 resched_cpu+0xd4/0x240 kernel/sched/core.c:994
 rcu_implicit_dynticks_qs+0x438/0xc30 kernel/rcu/tree.c:1329
 force_qs_rnp kernel/rcu/tree.c:2664 [inline]
 rcu_gp_fqs kernel/rcu/tree.c:-1 [inline]
 rcu_gp_fqs_loop+0x972/0x11b0 kernel/rcu/tree.c:1986
 rcu_gp_kthread+0x98/0x350 kernel/rcu/tree.c:2145
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>