====================================================== WARNING: possible circular locking dependency detected 6.12.0-rc4-syzkaller-00047-gc2ee9f594da8 #0 Not tainted ------------------------------------------------------ rcu_exp_gp_kthr/19 is trying to acquire lock: ffff8880b8629598 (krc.lock){..-.}-{2:2}, at: krc_this_cpu_lock kernel/rcu/tree.c:3312 [inline] ffff8880b8629598 (krc.lock){..-.}-{2:2}, at: add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3725 [inline] ffff8880b8629598 (krc.lock){..-.}-{2:2}, at: kvfree_call_rcu+0xda/0xbe0 kernel/rcu/tree.c:3811 but task is already holding lock: ffff8880b862a858 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x5d/0x220 kernel/time/timer.c:1051 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&base->lock){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162 lock_timer_base+0x5d/0x220 kernel/time/timer.c:1051 __mod_timer+0x426/0xdc0 kernel/time/timer.c:1132 add_timer_global+0x8a/0xc0 kernel/time/timer.c:1330 __queue_delayed_work+0x1ba/0x2e0 kernel/workqueue.c:2523 queue_delayed_work_on+0x12a/0x150 kernel/workqueue.c:2552 kvfree_call_rcu+0x749/0xbe0 kernel/rcu/tree.c:3839 pwq_release_workfn+0x4dd/0xa50 kernel/workqueue.c:5078 kthread_worker_fn+0x305/0xba0 kernel/kthread.c:844 kthread+0x2c1/0x3a0 kernel/kthread.c:389 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 -> #0 (krc.lock){..-.}-{2:2}: check_prev_add kernel/locking/lockdep.c:3161 [inline] check_prevs_add kernel/locking/lockdep.c:3280 [inline] validate_chain kernel/locking/lockdep.c:3904 [inline] __lock_acquire+0x250b/0x3ce0 kernel/locking/lockdep.c:5202 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5825 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 krc_this_cpu_lock kernel/rcu/tree.c:3312 [inline] add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3725 [inline] kvfree_call_rcu+0xda/0xbe0 kernel/rcu/tree.c:3811 trie_delete_elem+0x5c5/0x820 kernel/bpf/lpm_trie.c:540 bpf_prog_2e5e7763945ac34e+0x45/0x49 bpf_dispatcher_nop_func include/linux/bpf.h:1257 [inline] __bpf_prog_run include/linux/filter.h:701 [inline] bpf_prog_run include/linux/filter.h:708 [inline] __bpf_trace_run kernel/trace/bpf_trace.c:2318 [inline] bpf_trace_run2+0x231/0x590 kernel/trace/bpf_trace.c:2359 __bpf_trace_timer_start+0xc7/0x100 include/trace/events/timer.h:52 trace_timer_start include/trace/events/timer.h:52 [inline] enqueue_timer+0x2b4/0x550 kernel/time/timer.c:663 internal_add_timer kernel/time/timer.c:688 [inline] __mod_timer+0x8d7/0xdc0 kernel/time/timer.c:1183 schedule_timeout+0x131/0x2a0 kernel/time/timer.c:2614 synchronize_rcu_expedited_wait_once kernel/rcu/tree_exp.h:536 [inline] synchronize_rcu_expedited_wait kernel/rcu/tree_exp.h:649 [inline] rcu_exp_wait_wake+0x95b/0x1640 kernel/rcu/tree_exp.h:678 kthread_worker_fn+0x305/0xba0 kernel/kthread.c:844 kthread+0x2c1/0x3a0 kernel/kthread.c:389 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&base->lock); lock(krc.lock); lock(&base->lock); lock(krc.lock); *** DEADLOCK *** 2 locks held by rcu_exp_gp_kthr/19: #0: ffff8880b862a858 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x5d/0x220 kernel/time/timer.c:1051 #1: ffffffff8e1b8380 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline] #1: ffffffff8e1b8380 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #1: ffffffff8e1b8380 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2317 [inline] #1: ffffffff8e1b8380 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x1c2/0x590 kernel/trace/bpf_trace.c:2359 stack backtrace: CPU: 0 UID: 0 PID: 19 Comm: rcu_exp_gp_kthr Not tainted 6.12.0-rc4-syzkaller-00047-gc2ee9f594da8 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x41c/0x610 kernel/locking/lockdep.c:2074 check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2206 check_prev_add kernel/locking/lockdep.c:3161 [inline] check_prevs_add kernel/locking/lockdep.c:3280 [inline] validate_chain kernel/locking/lockdep.c:3904 [inline] __lock_acquire+0x250b/0x3ce0 kernel/locking/lockdep.c:5202 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5825 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 krc_this_cpu_lock kernel/rcu/tree.c:3312 [inline] add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3725 [inline] kvfree_call_rcu+0xda/0xbe0 kernel/rcu/tree.c:3811 trie_delete_elem+0x5c5/0x820 kernel/bpf/lpm_trie.c:540 bpf_prog_2e5e7763945ac34e+0x45/0x49 bpf_dispatcher_nop_func include/linux/bpf.h:1257 [inline] __bpf_prog_run include/linux/filter.h:701 [inline] bpf_prog_run include/linux/filter.h:708 [inline] __bpf_trace_run kernel/trace/bpf_trace.c:2318 [inline] bpf_trace_run2+0x231/0x590 kernel/trace/bpf_trace.c:2359 __bpf_trace_timer_start+0xc7/0x100 include/trace/events/timer.h:52 trace_timer_start include/trace/events/timer.h:52 [inline] enqueue_timer+0x2b4/0x550 kernel/time/timer.c:663 internal_add_timer kernel/time/timer.c:688 [inline] __mod_timer+0x8d7/0xdc0 kernel/time/timer.c:1183 schedule_timeout+0x131/0x2a0 kernel/time/timer.c:2614 synchronize_rcu_expedited_wait_once kernel/rcu/tree_exp.h:536 [inline] synchronize_rcu_expedited_wait kernel/rcu/tree_exp.h:649 [inline] rcu_exp_wait_wake+0x95b/0x1640 kernel/rcu/tree_exp.h:678 kthread_worker_fn+0x305/0xba0 kernel/kthread.c:844 kthread+0x2c1/0x3a0 kernel/kthread.c:389 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244