Hi, The following warning can be triggered by attaching/detaching the prog in the link multiple times. This is related to a previous report: https://lore.kernel.org/bpf/Y4%2F27g8EHQ9F3bDr@xxxxxxxxxx/T/#t Seems hard to prevent this, especially with kprobe. This can be reproduced on: HEAD commit: ab0350c743d5 selftests/bpf: Fix conflicts with built-in functions in bpf_iter_ksym git tree: bpf-next console log: https://pastebin.com/raw/khH3sQVG kernel config: https://pastebin.com/raw/77bXX2Wb BPF prog: https://pastebin.com/raw/A43uNuP1 ================================ WARNING: inconsistent lock state 6.1.0-rc7-01489-gab0350c743d5 #120 Not tainted -------------------------------- inconsistent {INITIAL USE} -> {IN-NMI} usage. kprobe/6606 [HC1[1]:SC0[0]:HE0:SE1] takes: ffffffff8d41bfb8 (trace_printk_lock){....}-{2:2}, at: ____bpf_trace_printk kernel/trace/bpf_trace.c:391 [inline] ffffffff8d41bfb8 (trace_printk_lock){....}-{2:2}, at: bpf_trace_printk+0xd3/0x170 kernel/trace/bpf_trace.c:377 {INITIAL USE} state was registered at: lock_acquire kernel/locking/lockdep.c:5668 [inline] lock_acquire+0x1e0/0x610 kernel/locking/lockdep.c:5633 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x3a/0x50 kernel/locking/spinlock.c:162 ____bpf_trace_printk kernel/trace/bpf_trace.c:391 [inline] bpf_trace_printk+0xd3/0x170 kernel/trace/bpf_trace.c:377 bpf_prog_cf2ac6d483d8499b_trace_bpf_trace_printk+0x2b/0x37 bpf_dispatcher_nop_func include/linux/bpf.h:1082 [inline] __bpf_prog_run include/linux/filter.h:600 [inline] bpf_prog_run include/linux/filter.h:607 [inline] bpf_prog_run_array include/linux/bpf.h:1728 [inline] trace_call_bpf+0x280/0x660 kernel/trace/bpf_trace.c:136 kprobe_perf_func+0x107/0x860 kernel/trace/trace_kprobe.c:1522 kprobe_dispatcher+0xe6/0x180 kernel/trace/trace_kprobe.c:1665 opt_pre_handler+0xd9/0x160 kernel/kprobes.c:429 optimized_callback arch/x86/kernel/kprobes/opt.c:199 [inline] optimized_callback+0x221/0x2b0 arch/x86/kernel/kprobes/opt.c:176 0xffffffffa0403034 pgdat_kswapd_lock include/linux/memory_hotplug.h:213 [inline] kswapd_is_running mm/compaction.c:1987 [inline] should_proactive_compact_node mm/compaction.c:2060 [inline] kcompactd+0x2cb/0xeb0 mm/compaction.c:2979 irq event stamp: 14116 hardirqs last enabled at (14115): [<ffffffff81d074f2>] kasan_quarantine_put+0x102/0x230 mm/kasan/quarantine.c:242 hardirqs last disabled at (14116): [<ffffffff89f217a3>] exc_int3+0x23/0x80 arch/x86/kernel/traps.c:843 softirqs last enabled at (14102): [<ffffffff81917290>] spin_unlock_bh include/linux/spinlock.h:395 [inline] softirqs last enabled at (14102): [<ffffffff81917290>] bpf_link_settle kernel/bpf/syscall.c:2879 [inline] softirqs last enabled at (14102): [<ffffffff81917290>] bpf_perf_link_attach+0x360/0x520 kernel/bpf/syscall.c:3283 softirqs last disabled at (14100): [<ffffffff81917253>] spin_lock_bh include/linux/spinlock.h:355 [inline] softirqs last disabled at (14100): [<ffffffff81917253>] bpf_link_settle kernel/bpf/syscall.c:2877 [inline] softirqs last disabled at (14100): [<ffffffff81917253>] bpf_perf_link_attach+0x323/0x520 kernel/bpf/syscall.c:3283 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(trace_printk_lock); <Interrupt> lock(trace_printk_lock); *** DEADLOCK *** 1 lock held by kprobe/6606: #0: ffff8880b98412b0 (&cpuctx_mutex){+.+.}-{3:3}, at: perf_event_ctx_lock_nested+0x227/0x480 kernel/events/core.c:1297 stack backtrace: CPU: 0 PID: 6606 Comm: kprobe Not tainted 6.1.0-rc7-01489-gab0350c743d5 #120 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.16.1-1-1 04/01/2014 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x100/0x178 lib/dump_stack.c:106 print_usage_bug include/trace/events/lock.h:24 [inline] verify_lock_unused kernel/locking/lockdep.c:5600 [inline] lock_acquire kernel/locking/lockdep.c:5659 [inline] lock_acquire.cold+0x3b/0x40 kernel/locking/lockdep.c:5633 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x3a/0x50 kernel/locking/spinlock.c:162 ____bpf_trace_printk kernel/trace/bpf_trace.c:391 [inline] bpf_trace_printk+0xd3/0x170 kernel/trace/bpf_trace.c:377 bpf_prog_cf2ac6d483d8499b_trace_bpf_trace_printk+0x33/0x37 bpf_dispatcher_nop_func include/linux/bpf.h:1082 [inline] __bpf_prog_run include/linux/filter.h:600 [inline] bpf_prog_run include/linux/filter.h:607 [inline] bpf_prog_run_array include/linux/bpf.h:1728 [inline] trace_call_bpf+0x280/0x660 kernel/trace/bpf_trace.c:136 kprobe_perf_func+0x107/0x860 kernel/trace/trace_kprobe.c:1522 kprobe_dispatcher+0xe6/0x180 kernel/trace/trace_kprobe.c:1665 aggr_pre_handler+0xdd/0x180 kernel/kprobes.c:1202 kprobe_int3_handler+0x442/0x560 arch/x86/kernel/kprobes/core.c:981 do_int3+0xd/0x50 arch/x86/kernel/traps.c:800 exc_int3+0x2d/0x80 arch/x86/kernel/traps.c:846 asm_exc_int3+0x39/0x40 arch/x86/include/asm/idtentry.h:569 RIP: 0010:trace_contention_begin+0x1/0x1e0 include/trace/events/lock.h:95 Code: f5 2b 6e 00 e9 7d fe ff ff 48 89 df e8 e8 2b 6e 00 e9 ea fe ff ff e8 fe 2b 6e 00 e9 43 ff ff ff 66 0f 1f 84 00 00 00 00 00 cc <55> 41 54 55 53 66 90 48 c7 c3 80 b7 32 8f 65 8b 2d f2 de 9f 7e 48 RSP: 0018:ffffc9000be87cb0 EFLAGS: 00000282 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000001 RDX: 1ffff11004068149 RSI: 0000000000000021 RDI: ffff8880b9841248 RBP: ffffc9000be87e10 R08: 0000000000000000 R09: ffffffff91ee6a4f R10: fffffbfff23dcd49 R11: 0000000000000000 R12: 0000000000000000 R13: dffffc0000000000 R14: ffff8880b9841248 R15: ffffed10026611c0 __mutex_lock_common kernel/locking/mutex.c:605 [inline] __mutex_lock+0x15a/0x12e0 kernel/locking/mutex.c:747 perf_event_ctx_lock_nested+0x227/0x480 kernel/events/core.c:1297 perf_event_ctx_lock kernel/events/core.c:1310 [inline] perf_ioctl+0x67/0xb0 kernel/events/core.c:5754 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x189/0x210 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f9e448e1017 Code: 00 00 00 48 8b 05 81 7e 2b 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 51 7e 2b 00 f7 d8 64 89 01 48 RSP: 002b:00007ffc65e35c48 EFLAGS: 00000206 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000007 RCX: 00007f9e448e1017 RDX: 0000000000000000 RSI: 0000000000002400 RDI: 0000000000000006 RBP: 0000000000000001 R08: 0000000727d65330 R09: 0000000500000000 R10: 0000000000000541 R11: 0000000000000206 R12: 0000000000000005 R13: 000055f027d65f70 R14: 0000000000000006 R15: 000055f027d65350 </TASK> ---------------- Code disassembly (best guess): 0: f5 cmc 1: 2b 6e 00 sub 0x0(%rsi),%ebp 4: e9 7d fe ff ff jmp 0xfffffe86 9: 48 89 df mov %rbx,%rdi c: e8 e8 2b 6e 00 call 0x6e2bf9 11: e9 ea fe ff ff jmp 0xffffff00 16: e8 fe 2b 6e 00 call 0x6e2c19 1b: e9 43 ff ff ff jmp 0xffffff63 20: 66 0f 1f 84 00 00 00 nopw 0x0(%rax,%rax,1) 27: 00 00 29: cc int3 * 2a: 55 push %rbp <-- trapping instruction 2b: 41 54 push %r12 2d: 55 push %rbp 2e: 53 push %rbx 2f: 66 90 xchg %ax,%ax 31: 48 c7 c3 80 b7 32 8f mov $0xffffffff8f32b780,%rbx 38: 65 8b 2d f2 de 9f 7e mov %gs:0x7e9fdef2(%rip),%ebp # 0x7e9fdf31 3f: 48 rex.W
